diff options
Diffstat (limited to 'mm/gup.c')
| -rw-r--r-- | mm/gup.c | 3728 |
1 files changed, 2698 insertions, 1030 deletions
@@ -1,61 +1,777 @@ +// SPDX-License-Identifier: GPL-2.0-only #include <linux/kernel.h> #include <linux/errno.h> #include <linux/err.h> #include <linux/spinlock.h> #include <linux/mm.h> +#include <linux/memfd.h> #include <linux/memremap.h> #include <linux/pagemap.h> #include <linux/rmap.h> #include <linux/swap.h> #include <linux/swapops.h> +#include <linux/secretmem.h> #include <linux/sched/signal.h> #include <linux/rwsem.h> #include <linux/hugetlb.h> +#include <linux/migrate.h> +#include <linux/mm_inline.h> +#include <linux/pagevec.h> +#include <linux/sched/mm.h> +#include <linux/shmem_fs.h> #include <asm/mmu_context.h> -#include <asm/pgtable.h> #include <asm/tlbflush.h> #include "internal.h" +#include "swap.h" -struct follow_page_context { - struct dev_pagemap *pgmap; - unsigned int page_mask; -}; +static inline void sanity_check_pinned_pages(struct page **pages, + unsigned long npages) +{ + if (!IS_ENABLED(CONFIG_DEBUG_VM)) + return; + + /* + * We only pin anonymous pages if they are exclusive. Once pinned, we + * can no longer turn them possibly shared and PageAnonExclusive() will + * stick around until the page is freed. + * + * We'd like to verify that our pinned anonymous pages are still mapped + * exclusively. The issue with anon THP is that we don't know how + * they are/were mapped when pinning them. However, for anon + * THP we can assume that either the given page (PTE-mapped THP) or + * the head page (PMD-mapped THP) should be PageAnonExclusive(). If + * neither is the case, there is certainly something wrong. + */ + for (; npages; npages--, pages++) { + struct page *page = *pages; + struct folio *folio; + + if (!page) + continue; + + folio = page_folio(page); + + if (is_zero_page(page) || + !folio_test_anon(folio)) + continue; + if (!folio_test_large(folio) || folio_test_hugetlb(folio)) + VM_WARN_ON_ONCE_FOLIO(!PageAnonExclusive(&folio->page), folio); + else + /* Either a PTE-mapped or a PMD-mapped THP. */ + VM_WARN_ON_ONCE_PAGE(!PageAnonExclusive(&folio->page) && + !PageAnonExclusive(page), page); + } +} + +/* + * Return the folio with ref appropriately incremented, + * or NULL if that failed. + */ +static inline struct folio *try_get_folio(struct page *page, int refs) +{ + struct folio *folio; + +retry: + folio = page_folio(page); + if (WARN_ON_ONCE(folio_ref_count(folio) < 0)) + return NULL; + if (unlikely(!folio_ref_try_add(folio, refs))) + return NULL; + + /* + * At this point we have a stable reference to the folio; but it + * could be that between calling page_folio() and the refcount + * increment, the folio was split, in which case we'd end up + * holding a reference on a folio that has nothing to do with the page + * we were given anymore. + * So now that the folio is stable, recheck that the page still + * belongs to this folio. + */ + if (unlikely(page_folio(page) != folio)) { + folio_put_refs(folio, refs); + goto retry; + } + + return folio; +} + +static void gup_put_folio(struct folio *folio, int refs, unsigned int flags) +{ + if (flags & FOLL_PIN) { + if (is_zero_folio(folio)) + return; + node_stat_mod_folio(folio, NR_FOLL_PIN_RELEASED, refs); + if (folio_has_pincount(folio)) + atomic_sub(refs, &folio->_pincount); + else + refs *= GUP_PIN_COUNTING_BIAS; + } + + folio_put_refs(folio, refs); +} + +/** + * try_grab_folio() - add a folio's refcount by a flag-dependent amount + * @folio: pointer to folio to be grabbed + * @refs: the value to (effectively) add to the folio's refcount + * @flags: gup flags: these are the FOLL_* flag values + * + * This might not do anything at all, depending on the flags argument. + * + * "grab" names in this file mean, "look at flags to decide whether to use + * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount. + * + * Either FOLL_PIN or FOLL_GET (or neither) may be set, but not both at the same + * time. + * + * Return: 0 for success, or if no action was required (if neither FOLL_PIN + * nor FOLL_GET was set, nothing is done). A negative error code for failure: + * + * -ENOMEM FOLL_GET or FOLL_PIN was set, but the folio could not + * be grabbed. + * + * It is called when we have a stable reference for the folio, typically in + * GUP slow path. + */ +int __must_check try_grab_folio(struct folio *folio, int refs, + unsigned int flags) +{ + if (WARN_ON_ONCE(folio_ref_count(folio) <= 0)) + return -ENOMEM; + + if (unlikely(!(flags & FOLL_PCI_P2PDMA) && folio_is_pci_p2pdma(folio))) + return -EREMOTEIO; + + if (flags & FOLL_GET) + folio_ref_add(folio, refs); + else if (flags & FOLL_PIN) { + /* + * Don't take a pin on the zero page - it's not going anywhere + * and it is used in a *lot* of places. + */ + if (is_zero_folio(folio)) + return 0; + + /* + * Increment the normal page refcount field at least once, + * so that the page really is pinned. + */ + if (folio_has_pincount(folio)) { + folio_ref_add(folio, refs); + atomic_add(refs, &folio->_pincount); + } else { + folio_ref_add(folio, refs * GUP_PIN_COUNTING_BIAS); + } + + node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs); + } + + return 0; +} + +/** + * unpin_user_page() - release a dma-pinned page + * @page: pointer to page to be released + * + * Pages that were pinned via pin_user_pages*() must be released via either + * unpin_user_page(), or one of the unpin_user_pages*() routines. This is so + * that such pages can be separately tracked and uniquely handled. In + * particular, interactions with RDMA and filesystems need special handling. + */ +void unpin_user_page(struct page *page) +{ + sanity_check_pinned_pages(&page, 1); + gup_put_folio(page_folio(page), 1, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_user_page); + +/** + * unpin_folio() - release a dma-pinned folio + * @folio: pointer to folio to be released + * + * Folios that were pinned via memfd_pin_folios() or other similar routines + * must be released either using unpin_folio() or unpin_folios(). + */ +void unpin_folio(struct folio *folio) +{ + gup_put_folio(folio, 1, FOLL_PIN); +} +EXPORT_SYMBOL_GPL(unpin_folio); + +/** + * folio_add_pin - Try to get an additional pin on a pinned folio + * @folio: The folio to be pinned + * + * Get an additional pin on a folio we already have a pin on. Makes no change + * if the folio is a zero_page. + */ +void folio_add_pin(struct folio *folio) +{ + if (is_zero_folio(folio)) + return; + + /* + * Similar to try_grab_folio(): be sure to *also* increment the normal + * page refcount field at least once, so that the page really is + * pinned. + */ + if (folio_has_pincount(folio)) { + WARN_ON_ONCE(atomic_read(&folio->_pincount) < 1); + folio_ref_inc(folio); + atomic_inc(&folio->_pincount); + } else { + WARN_ON_ONCE(folio_ref_count(folio) < GUP_PIN_COUNTING_BIAS); + folio_ref_add(folio, GUP_PIN_COUNTING_BIAS); + } +} + +static inline struct folio *gup_folio_range_next(struct page *start, + unsigned long npages, unsigned long i, unsigned int *ntails) +{ + struct page *next = start + i; + struct folio *folio = page_folio(next); + unsigned int nr = 1; + + if (folio_test_large(folio)) + nr = min_t(unsigned int, npages - i, + folio_nr_pages(folio) - folio_page_idx(folio, next)); + + *ntails = nr; + return folio; +} + +static inline struct folio *gup_folio_next(struct page **list, + unsigned long npages, unsigned long i, unsigned int *ntails) +{ + struct folio *folio = page_folio(list[i]); + unsigned int nr; + + for (nr = i + 1; nr < npages; nr++) { + if (page_folio(list[nr]) != folio) + break; + } + + *ntails = nr - i; + return folio; +} + +/** + * unpin_user_pages_dirty_lock() - release and optionally dirty gup-pinned pages + * @pages: array of pages to be maybe marked dirty, and definitely released. + * @npages: number of pages in the @pages array. + * @make_dirty: whether to mark the pages dirty + * + * "gup-pinned page" refers to a page that has had one of the get_user_pages() + * variants called on that page. + * + * For each page in the @pages array, make that page (or its head page, if a + * compound page) dirty, if @make_dirty is true, and if the page was previously + * listed as clean. In any case, releases all pages using unpin_user_page(), + * possibly via unpin_user_pages(), for the non-dirty case. + * + * Please see the unpin_user_page() documentation for details. + * + * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is + * required, then the caller should a) verify that this is really correct, + * because _lock() is usually required, and b) hand code it: + * set_page_dirty_lock(), unpin_user_page(). + * + */ +void unpin_user_pages_dirty_lock(struct page **pages, unsigned long npages, + bool make_dirty) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + if (!make_dirty) { + unpin_user_pages(pages, npages); + return; + } + + sanity_check_pinned_pages(pages, npages); + for (i = 0; i < npages; i += nr) { + folio = gup_folio_next(pages, npages, i, &nr); + /* + * Checking PageDirty at this point may race with + * clear_page_dirty_for_io(), but that's OK. Two key + * cases: + * + * 1) This code sees the page as already dirty, so it + * skips the call to set_page_dirty(). That could happen + * because clear_page_dirty_for_io() called + * folio_mkclean(), followed by set_page_dirty(). + * However, now the page is going to get written back, + * which meets the original intention of setting it + * dirty, so all is well: clear_page_dirty_for_io() goes + * on to call TestClearPageDirty(), and write the page + * back. + * + * 2) This code sees the page as clean, so it calls + * set_page_dirty(). The page stays dirty, despite being + * written back, so it gets written back again in the + * next writeback cycle. This is harmless. + */ + if (!folio_test_dirty(folio)) { + folio_lock(folio); + folio_mark_dirty(folio); + folio_unlock(folio); + } + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_pages_dirty_lock); + +/** + * unpin_user_page_range_dirty_lock() - release and optionally dirty + * gup-pinned page range + * + * @page: the starting page of a range maybe marked dirty, and definitely released. + * @npages: number of consecutive pages to release. + * @make_dirty: whether to mark the pages dirty + * + * "gup-pinned page range" refers to a range of pages that has had one of the + * pin_user_pages() variants called on that page. + * + * The page range must be truly physically contiguous: the page range + * corresponds to a contiguous PFN range and all pages can be iterated + * naturally. + * + * For the page ranges defined by [page .. page+npages], make that range (or + * its head pages, if a compound page) dirty, if @make_dirty is true, and if the + * page range was previously listed as clean. + * + * set_page_dirty_lock() is used internally. If instead, set_page_dirty() is + * required, then the caller should a) verify that this is really correct, + * because _lock() is usually required, and b) hand code it: + * set_page_dirty_lock(), unpin_user_page(). + * + */ +void unpin_user_page_range_dirty_lock(struct page *page, unsigned long npages, + bool make_dirty) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + VM_WARN_ON_ONCE(!page_range_contiguous(page, npages)); + + for (i = 0; i < npages; i += nr) { + folio = gup_folio_range_next(page, npages, i, &nr); + if (make_dirty && !folio_test_dirty(folio)) { + folio_lock(folio); + folio_mark_dirty(folio); + folio_unlock(folio); + } + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_page_range_dirty_lock); + +static void gup_fast_unpin_user_pages(struct page **pages, unsigned long npages) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + /* + * Don't perform any sanity checks because we might have raced with + * fork() and some anonymous pages might now actually be shared -- + * which is why we're unpinning after all. + */ + for (i = 0; i < npages; i += nr) { + folio = gup_folio_next(pages, npages, i, &nr); + gup_put_folio(folio, nr, FOLL_PIN); + } +} + +/** + * unpin_user_pages() - release an array of gup-pinned pages. + * @pages: array of pages to be marked dirty and released. + * @npages: number of pages in the @pages array. + * + * For each page in the @pages array, release the page using unpin_user_page(). + * + * Please see the unpin_user_page() documentation for details. + */ +void unpin_user_pages(struct page **pages, unsigned long npages) +{ + unsigned long i; + struct folio *folio; + unsigned int nr; + + /* + * If this WARN_ON() fires, then the system *might* be leaking pages (by + * leaving them pinned), but probably not. More likely, gup/pup returned + * a hard -ERRNO error to the caller, who erroneously passed it here. + */ + if (WARN_ON(IS_ERR_VALUE(npages))) + return; + + sanity_check_pinned_pages(pages, npages); + for (i = 0; i < npages; i += nr) { + if (!pages[i]) { + nr = 1; + continue; + } + folio = gup_folio_next(pages, npages, i, &nr); + gup_put_folio(folio, nr, FOLL_PIN); + } +} +EXPORT_SYMBOL(unpin_user_pages); + +/** + * unpin_user_folio() - release pages of a folio + * @folio: pointer to folio to be released + * @npages: number of pages of same folio + * + * Release npages of the folio + */ +void unpin_user_folio(struct folio *folio, unsigned long npages) +{ + gup_put_folio(folio, npages, FOLL_PIN); +} +EXPORT_SYMBOL(unpin_user_folio); + +/** + * unpin_folios() - release an array of gup-pinned folios. + * @folios: array of folios to be marked dirty and released. + * @nfolios: number of folios in the @folios array. + * + * For each folio in the @folios array, release the folio using gup_put_folio. + * + * Please see the unpin_folio() documentation for details. + */ +void unpin_folios(struct folio **folios, unsigned long nfolios) +{ + unsigned long i = 0, j; + + /* + * If this WARN_ON() fires, then the system *might* be leaking folios + * (by leaving them pinned), but probably not. More likely, gup/pup + * returned a hard -ERRNO error to the caller, who erroneously passed + * it here. + */ + if (WARN_ON(IS_ERR_VALUE(nfolios))) + return; + + while (i < nfolios) { + for (j = i + 1; j < nfolios; j++) + if (folios[i] != folios[j]) + break; + + if (folios[i]) + gup_put_folio(folios[i], j - i, FOLL_PIN); + i = j; + } +} +EXPORT_SYMBOL_GPL(unpin_folios); + +/* + * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for the mm's + * lifecycle. Avoid setting the bit unless necessary, or it might cause write + * cache bouncing on large SMP machines for concurrent pinned gups. + */ +static inline void mm_set_has_pinned_flag(struct mm_struct *mm) +{ + if (!mm_flags_test(MMF_HAS_PINNED, mm)) + mm_flags_set(MMF_HAS_PINNED, mm); +} + +#ifdef CONFIG_MMU + +#ifdef CONFIG_HAVE_GUP_FAST +/** + * try_grab_folio_fast() - Attempt to get or pin a folio in fast path. + * @page: pointer to page to be grabbed + * @refs: the value to (effectively) add to the folio's refcount + * @flags: gup flags: these are the FOLL_* flag values. + * + * "grab" names in this file mean, "look at flags to decide whether to use + * FOLL_PIN or FOLL_GET behavior, when incrementing the folio's refcount. + * + * Either FOLL_PIN or FOLL_GET (or neither) must be set, but not both at the + * same time. (That's true throughout the get_user_pages*() and + * pin_user_pages*() APIs.) Cases: + * + * FOLL_GET: folio's refcount will be incremented by @refs. + * + * FOLL_PIN on large folios: folio's refcount will be incremented by + * @refs, and its pincount will be incremented by @refs. + * + * FOLL_PIN on single-page folios: folio's refcount will be incremented by + * @refs * GUP_PIN_COUNTING_BIAS. + * + * Return: The folio containing @page (with refcount appropriately + * incremented) for success, or NULL upon failure. If neither FOLL_GET + * nor FOLL_PIN was set, that's considered failure, and furthermore, + * a likely bug in the caller, so a warning is also emitted. + * + * It uses add ref unless zero to elevate the folio refcount and must be called + * in fast path only. + */ +static struct folio *try_grab_folio_fast(struct page *page, int refs, + unsigned int flags) +{ + struct folio *folio; + + /* Raise warn if it is not called in fast GUP */ + VM_WARN_ON_ONCE(!irqs_disabled()); + + if (WARN_ON_ONCE((flags & (FOLL_GET | FOLL_PIN)) == 0)) + return NULL; + + if (unlikely(!(flags & FOLL_PCI_P2PDMA) && is_pci_p2pdma_page(page))) + return NULL; + + if (flags & FOLL_GET) + return try_get_folio(page, refs); + + /* FOLL_PIN is set */ + + /* + * Don't take a pin on the zero page - it's not going anywhere + * and it is used in a *lot* of places. + */ + if (is_zero_page(page)) + return page_folio(page); + + folio = try_get_folio(page, refs); + if (!folio) + return NULL; + + /* + * Can't do FOLL_LONGTERM + FOLL_PIN gup fast path if not in a + * right zone, so fail and let the caller fall back to the slow + * path. + */ + if (unlikely((flags & FOLL_LONGTERM) && + !folio_is_longterm_pinnable(folio))) { + folio_put_refs(folio, refs); + return NULL; + } + + /* + * When pinning a large folio, use an exact count to track it. + * + * However, be sure to *also* increment the normal folio + * refcount field at least once, so that the folio really + * is pinned. That's why the refcount from the earlier + * try_get_folio() is left intact. + */ + if (folio_has_pincount(folio)) + atomic_add(refs, &folio->_pincount); + else + folio_ref_add(folio, + refs * (GUP_PIN_COUNTING_BIAS - 1)); + /* + * Adjust the pincount before re-checking the PTE for changes. + * This is essentially a smp_mb() and is paired with a memory + * barrier in folio_try_share_anon_rmap_*(). + */ + smp_mb__after_atomic(); + + node_stat_mod_folio(folio, NR_FOLL_PIN_ACQUIRED, refs); + + return folio; +} +#endif /* CONFIG_HAVE_GUP_FAST */ + +/* Common code for can_follow_write_* */ +static inline bool can_follow_write_common(struct page *page, + struct vm_area_struct *vma, unsigned int flags) +{ + /* Maybe FOLL_FORCE is set to override it? */ + if (!(flags & FOLL_FORCE)) + return false; + + /* But FOLL_FORCE has no effect on shared mappings */ + if (vma->vm_flags & (VM_MAYSHARE | VM_SHARED)) + return false; + + /* ... or read-only private ones */ + if (!(vma->vm_flags & VM_MAYWRITE)) + return false; + + /* ... or already writable ones that just need to take a write fault */ + if (vma->vm_flags & VM_WRITE) + return false; + + /* + * See can_change_pte_writable(): we broke COW and could map the page + * writable if we have an exclusive anonymous page ... + */ + return page && PageAnon(page) && PageAnonExclusive(page); +} static struct page *no_page_table(struct vm_area_struct *vma, - unsigned int flags) + unsigned int flags, unsigned long address) { + if (!(flags & FOLL_DUMP)) + return NULL; + /* - * When core dumping an enormous anonymous area that nobody - * has touched so far, we don't want to allocate unnecessary pages or + * When core dumping, we don't want to allocate unnecessary pages or * page tables. Return error instead of NULL to skip handle_mm_fault, * then get_dump_page() will return NULL to leave a hole in the dump. * But we can only make this optimization where a hole would surely * be zero-filled if handle_mm_fault() actually did handle it. */ - if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma->vm_ops->fault)) + if (is_vm_hugetlb_page(vma)) { + struct hstate *h = hstate_vma(vma); + + if (!hugetlbfs_pagecache_present(h, vma, address)) + return ERR_PTR(-EFAULT); + } else if ((vma_is_anonymous(vma) || !vma->vm_ops->fault)) { + return ERR_PTR(-EFAULT); + } + + return NULL; +} + +#ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES +/* FOLL_FORCE can write to even unwritable PUDs in COW mappings. */ +static inline bool can_follow_write_pud(pud_t pud, struct page *page, + struct vm_area_struct *vma, + unsigned int flags) +{ + /* If the pud is writable, we can write to the page. */ + if (pud_write(pud)) + return true; + + return can_follow_write_common(page, vma, flags); +} + +static struct page *follow_huge_pud(struct vm_area_struct *vma, + unsigned long addr, pud_t *pudp, + int flags, unsigned long *page_mask) +{ + struct mm_struct *mm = vma->vm_mm; + struct page *page; + pud_t pud = *pudp; + unsigned long pfn = pud_pfn(pud); + int ret; + + assert_spin_locked(pud_lockptr(mm, pudp)); + + if (!pud_present(pud)) + return NULL; + + if ((flags & FOLL_WRITE) && + !can_follow_write_pud(pud, pfn_to_page(pfn), vma, flags)) + return NULL; + + pfn += (addr & ~PUD_MASK) >> PAGE_SHIFT; + page = pfn_to_page(pfn); + + if (!pud_write(pud) && gup_must_unshare(vma, flags, page)) + return ERR_PTR(-EMLINK); + + ret = try_grab_folio(page_folio(page), 1, flags); + if (ret) + page = ERR_PTR(ret); + else + *page_mask = HPAGE_PUD_NR - 1; + + return page; +} + +/* FOLL_FORCE can write to even unwritable PMDs in COW mappings. */ +static inline bool can_follow_write_pmd(pmd_t pmd, struct page *page, + struct vm_area_struct *vma, + unsigned int flags) +{ + /* If the pmd is writable, we can write to the page. */ + if (pmd_write(pmd)) + return true; + + if (!can_follow_write_common(page, vma, flags)) + return false; + + /* ... and a write-fault isn't required for other reasons. */ + if (pmd_needs_soft_dirty_wp(vma, pmd)) + return false; + return !userfaultfd_huge_pmd_wp(vma, pmd); +} + +static struct page *follow_huge_pmd(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmd, + unsigned int flags, + unsigned long *page_mask) +{ + struct mm_struct *mm = vma->vm_mm; + pmd_t pmdval = *pmd; + struct page *page; + int ret; + + assert_spin_locked(pmd_lockptr(mm, pmd)); + + page = pmd_page(pmdval); + if ((flags & FOLL_WRITE) && + !can_follow_write_pmd(pmdval, page, vma, flags)) + return NULL; + + /* Avoid dumping huge zero page */ + if ((flags & FOLL_DUMP) && is_huge_zero_pmd(pmdval)) return ERR_PTR(-EFAULT); + + if (pmd_protnone(*pmd) && !gup_can_follow_protnone(vma, flags)) + return NULL; + + if (!pmd_write(pmdval) && gup_must_unshare(vma, flags, page)) + return ERR_PTR(-EMLINK); + + VM_WARN_ON_ONCE_PAGE((flags & FOLL_PIN) && PageAnon(page) && + !PageAnonExclusive(page), page); + + ret = try_grab_folio(page_folio(page), 1, flags); + if (ret) + return ERR_PTR(ret); + +#ifdef CONFIG_TRANSPARENT_HUGEPAGE + if (pmd_trans_huge(pmdval) && (flags & FOLL_TOUCH)) + touch_pmd(vma, addr, pmd, flags & FOLL_WRITE); +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + + page += (addr & ~HPAGE_PMD_MASK) >> PAGE_SHIFT; + *page_mask = HPAGE_PMD_NR - 1; + + return page; +} + +#else /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */ +static struct page *follow_huge_pud(struct vm_area_struct *vma, + unsigned long addr, pud_t *pudp, + int flags, unsigned long *page_mask) +{ + return NULL; +} + +static struct page *follow_huge_pmd(struct vm_area_struct *vma, + unsigned long addr, pmd_t *pmd, + unsigned int flags, + unsigned long *page_mask) +{ return NULL; } +#endif /* CONFIG_PGTABLE_HAS_HUGE_LEAVES */ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, pte_t *pte, unsigned int flags) { - /* No page to get reference */ - if (flags & FOLL_GET) - return -EFAULT; - if (flags & FOLL_TOUCH) { - pte_t entry = *pte; + pte_t orig_entry = ptep_get(pte); + pte_t entry = orig_entry; if (flags & FOLL_WRITE) entry = pte_mkdirty(entry); entry = pte_mkyoung(entry); - if (!pte_same(*pte, entry)) { + if (!pte_same(orig_entry, entry)) { set_pte_at(vma->vm_mm, address, pte, entry); update_mmu_cache(vma, address, pte); } @@ -65,68 +781,55 @@ static int follow_pfn_pte(struct vm_area_struct *vma, unsigned long address, return -EEXIST; } -/* - * FOLL_FORCE can write to even unwritable pte's, but only - * after we've gone through a COW cycle and they are dirty. - */ -static inline bool can_follow_write_pte(pte_t pte, unsigned int flags) +/* FOLL_FORCE can write to even unwritable PTEs in COW mappings. */ +static inline bool can_follow_write_pte(pte_t pte, struct page *page, + struct vm_area_struct *vma, + unsigned int flags) { - return pte_write(pte) || - ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte)); + /* If the pte is writable, we can write to the page. */ + if (pte_write(pte)) + return true; + + if (!can_follow_write_common(page, vma, flags)) + return false; + + /* ... and a write-fault isn't required for other reasons. */ + if (pte_needs_soft_dirty_wp(vma, pte)) + return false; + return !userfaultfd_pte_wp(vma, pte); } static struct page *follow_page_pte(struct vm_area_struct *vma, - unsigned long address, pmd_t *pmd, unsigned int flags, - struct dev_pagemap **pgmap) + unsigned long address, pmd_t *pmd, unsigned int flags) { struct mm_struct *mm = vma->vm_mm; + struct folio *folio; struct page *page; spinlock_t *ptl; pte_t *ptep, pte; - -retry: - if (unlikely(pmd_bad(*pmd))) - return no_page_table(vma, flags); + int ret; ptep = pte_offset_map_lock(mm, pmd, address, &ptl); - pte = *ptep; - if (!pte_present(pte)) { - swp_entry_t entry; - /* - * KSM's break_ksm() relies upon recognizing a ksm page - * even while it is being migrated, so for that case we - * need migration_entry_wait(). - */ - if (likely(!(flags & FOLL_MIGRATION))) - goto no_page; - if (pte_none(pte)) - goto no_page; - entry = pte_to_swp_entry(pte); - if (!is_migration_entry(entry)) - goto no_page; - pte_unmap_unlock(ptep, ptl); - migration_entry_wait(mm, pmd, address); - goto retry; - } - if ((flags & FOLL_NUMA) && pte_protnone(pte)) + if (!ptep) + return no_page_table(vma, flags, address); + pte = ptep_get(ptep); + if (!pte_present(pte)) + goto no_page; + if (pte_protnone(pte) && !gup_can_follow_protnone(vma, flags)) goto no_page; - if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags)) { - pte_unmap_unlock(ptep, ptl); - return NULL; - } page = vm_normal_page(vma, address, pte); - if (!page && pte_devmap(pte) && (flags & FOLL_GET)) { - /* - * Only return device mapping pages in the FOLL_GET case since - * they are only valid while holding the pgmap reference. - */ - *pgmap = get_dev_pagemap(pte_pfn(pte), *pgmap); - if (*pgmap) - page = pte_page(pte); - else - goto no_page; - } else if (unlikely(!page)) { + + /* + * We only care about anon pages in can_follow_write_pte(). + */ + if ((flags & FOLL_WRITE) && + !can_follow_write_pte(pte, page, vma, flags)) { + page = NULL; + goto out; + } + + if (unlikely(!page)) { if (flags & FOLL_DUMP) { /* Avoid special (like zero) pages in core dumps */ page = ERR_PTR(-EFAULT); @@ -136,65 +839,51 @@ retry: if (is_zero_pfn(pte_pfn(pte))) { page = pte_page(pte); } else { - int ret; - ret = follow_pfn_pte(vma, address, ptep, flags); page = ERR_PTR(ret); goto out; } } + folio = page_folio(page); - if (flags & FOLL_SPLIT && PageTransCompound(page)) { - int ret; - get_page(page); - pte_unmap_unlock(ptep, ptl); - lock_page(page); - ret = split_huge_page(page); - unlock_page(page); - put_page(page); - if (ret) - return ERR_PTR(ret); - goto retry; + if (!pte_write(pte) && gup_must_unshare(vma, flags, page)) { + page = ERR_PTR(-EMLINK); + goto out; } - if (flags & FOLL_GET) - get_page(page); + VM_WARN_ON_ONCE_PAGE((flags & FOLL_PIN) && PageAnon(page) && + !PageAnonExclusive(page), page); + + /* try_grab_folio() does nothing unless FOLL_GET or FOLL_PIN is set. */ + ret = try_grab_folio(folio, 1, flags); + if (unlikely(ret)) { + page = ERR_PTR(ret); + goto out; + } + + /* + * We need to make the page accessible if and only if we are going + * to access its content (the FOLL_PIN case). Please see + * Documentation/core-api/pin_user_pages.rst for details. + */ + if (flags & FOLL_PIN) { + ret = arch_make_folio_accessible(folio); + if (ret) { + unpin_user_page(page); + page = ERR_PTR(ret); + goto out; + } + } if (flags & FOLL_TOUCH) { if ((flags & FOLL_WRITE) && - !pte_dirty(pte) && !PageDirty(page)) - set_page_dirty(page); + !pte_dirty(pte) && !folio_test_dirty(folio)) + folio_mark_dirty(folio); /* * pte_mkyoung() would be more correct here, but atomic care * is needed to avoid losing the dirty bit: it is easier to use - * mark_page_accessed(). - */ - mark_page_accessed(page); - } - if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) { - /* Do not mlock pte-mapped THP */ - if (PageTransCompound(page)) - goto out; - - /* - * The preliminary mapping check is mainly to avoid the - * pointless overhead of lock_page on the ZERO_PAGE - * which might bounce very badly if there is contention. - * - * If the page is already locked, we don't need to - * handle it now - vmscan will handle it later if and - * when it attempts to reclaim the page. + * folio_mark_accessed(). */ - if (page->mapping && trylock_page(page)) { - lru_add_drain(); /* push cached pages to LRU */ - /* - * Because we lock page here, and migration is - * blocked by the pte's page reference, and we - * know the page is still mapped, we don't even - * need to check for file-cache page truncation. - */ - mlock_vma_page(page); - unlock_page(page); - } + folio_mark_accessed(folio); } out: pte_unmap_unlock(ptep, ptl); @@ -203,13 +892,13 @@ no_page: pte_unmap_unlock(ptep, ptl); if (!pte_none(pte)) return NULL; - return no_page_table(vma, flags); + return no_page_table(vma, flags, address); } static struct page *follow_pmd_mask(struct vm_area_struct *vma, unsigned long address, pud_t *pudp, unsigned int flags, - struct follow_page_context *ctx) + unsigned long *page_mask) { pmd_t *pmd, pmdval; spinlock_t *ptl; @@ -217,167 +906,82 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma, struct mm_struct *mm = vma->vm_mm; pmd = pmd_offset(pudp, address); - /* - * The READ_ONCE() will stabilize the pmdval in a register or - * on the stack so that it will stop changing under the code. - */ - pmdval = READ_ONCE(*pmd); + pmdval = pmdp_get_lockless(pmd); if (pmd_none(pmdval)) - return no_page_table(vma, flags); - if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) { - page = follow_huge_pmd(mm, address, pmd, flags); - if (page) - return page; - return no_page_table(vma, flags); - } - if (is_hugepd(__hugepd(pmd_val(pmdval)))) { - page = follow_huge_pd(vma, address, - __hugepd(pmd_val(pmdval)), flags, - PMD_SHIFT); - if (page) - return page; - return no_page_table(vma, flags); - } -retry: - if (!pmd_present(pmdval)) { - if (likely(!(flags & FOLL_MIGRATION))) - return no_page_table(vma, flags); - VM_BUG_ON(thp_migration_supported() && - !is_pmd_migration_entry(pmdval)); - if (is_pmd_migration_entry(pmdval)) - pmd_migration_entry_wait(mm, pmd); - pmdval = READ_ONCE(*pmd); - /* - * MADV_DONTNEED may convert the pmd to null because - * mmap_sem is held in read mode - */ - if (pmd_none(pmdval)) - return no_page_table(vma, flags); - goto retry; - } - if (pmd_devmap(pmdval)) { - ptl = pmd_lock(mm, pmd); - page = follow_devmap_pmd(vma, address, pmd, flags, &ctx->pgmap); - spin_unlock(ptl); - if (page) - return page; - } - if (likely(!pmd_trans_huge(pmdval))) - return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + return no_page_table(vma, flags, address); + if (!pmd_present(pmdval)) + return no_page_table(vma, flags, address); + if (likely(!pmd_leaf(pmdval))) + return follow_page_pte(vma, address, pmd, flags); - if ((flags & FOLL_NUMA) && pmd_protnone(pmdval)) - return no_page_table(vma, flags); + if (pmd_protnone(pmdval) && !gup_can_follow_protnone(vma, flags)) + return no_page_table(vma, flags, address); -retry_locked: ptl = pmd_lock(mm, pmd); - if (unlikely(pmd_none(*pmd))) { + pmdval = *pmd; + if (unlikely(!pmd_present(pmdval))) { spin_unlock(ptl); - return no_page_table(vma, flags); + return no_page_table(vma, flags, address); } - if (unlikely(!pmd_present(*pmd))) { + if (unlikely(!pmd_leaf(pmdval))) { spin_unlock(ptl); - if (likely(!(flags & FOLL_MIGRATION))) - return no_page_table(vma, flags); - pmd_migration_entry_wait(mm, pmd); - goto retry_locked; + return follow_page_pte(vma, address, pmd, flags); } - if (unlikely(!pmd_trans_huge(*pmd))) { + if (pmd_trans_huge(pmdval) && (flags & FOLL_SPLIT_PMD)) { spin_unlock(ptl); - return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); + split_huge_pmd(vma, pmd, address); + /* If pmd was left empty, stuff a page table in there quickly */ + return pte_alloc(mm, pmd) ? ERR_PTR(-ENOMEM) : + follow_page_pte(vma, address, pmd, flags); } - if (flags & FOLL_SPLIT) { - int ret; - page = pmd_page(*pmd); - if (is_huge_zero_page(page)) { - spin_unlock(ptl); - ret = 0; - split_huge_pmd(vma, pmd, address); - if (pmd_trans_unstable(pmd)) - ret = -EBUSY; - } else { - get_page(page); - spin_unlock(ptl); - lock_page(page); - ret = split_huge_page(page); - unlock_page(page); - put_page(page); - if (pmd_none(*pmd)) - return no_page_table(vma, flags); - } - - return ret ? ERR_PTR(ret) : - follow_page_pte(vma, address, pmd, flags, &ctx->pgmap); - } - page = follow_trans_huge_pmd(vma, address, pmd, flags); + page = follow_huge_pmd(vma, address, pmd, flags, page_mask); spin_unlock(ptl); - ctx->page_mask = HPAGE_PMD_NR - 1; return page; } static struct page *follow_pud_mask(struct vm_area_struct *vma, unsigned long address, p4d_t *p4dp, unsigned int flags, - struct follow_page_context *ctx) + unsigned long *page_mask) { - pud_t *pud; + pud_t *pudp, pud; spinlock_t *ptl; struct page *page; struct mm_struct *mm = vma->vm_mm; - pud = pud_offset(p4dp, address); - if (pud_none(*pud)) - return no_page_table(vma, flags); - if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) { - page = follow_huge_pud(mm, address, pud, flags); - if (page) - return page; - return no_page_table(vma, flags); - } - if (is_hugepd(__hugepd(pud_val(*pud)))) { - page = follow_huge_pd(vma, address, - __hugepd(pud_val(*pud)), flags, - PUD_SHIFT); - if (page) - return page; - return no_page_table(vma, flags); - } - if (pud_devmap(*pud)) { - ptl = pud_lock(mm, pud); - page = follow_devmap_pud(vma, address, pud, flags, &ctx->pgmap); + pudp = pud_offset(p4dp, address); + pud = pudp_get(pudp); + if (!pud_present(pud)) + return no_page_table(vma, flags, address); + if (pud_leaf(pud)) { + ptl = pud_lock(mm, pudp); + page = follow_huge_pud(vma, address, pudp, flags, page_mask); spin_unlock(ptl); if (page) return page; + return no_page_table(vma, flags, address); } - if (unlikely(pud_bad(*pud))) - return no_page_table(vma, flags); + if (unlikely(pud_bad(pud))) + return no_page_table(vma, flags, address); - return follow_pmd_mask(vma, address, pud, flags, ctx); + return follow_pmd_mask(vma, address, pudp, flags, page_mask); } static struct page *follow_p4d_mask(struct vm_area_struct *vma, unsigned long address, pgd_t *pgdp, unsigned int flags, - struct follow_page_context *ctx) + unsigned long *page_mask) { - p4d_t *p4d; - struct page *page; + p4d_t *p4dp, p4d; - p4d = p4d_offset(pgdp, address); - if (p4d_none(*p4d)) - return no_page_table(vma, flags); - BUILD_BUG_ON(p4d_huge(*p4d)); - if (unlikely(p4d_bad(*p4d))) - return no_page_table(vma, flags); - - if (is_hugepd(__hugepd(p4d_val(*p4d)))) { - page = follow_huge_pd(vma, address, - __hugepd(p4d_val(*p4d)), flags, - P4D_SHIFT); - if (page) - return page; - return no_page_table(vma, flags); - } - return follow_pud_mask(vma, address, p4d, flags, ctx); + p4dp = p4d_offset(pgdp, address); + p4d = p4dp_get(p4dp); + BUILD_BUG_ON(p4d_leaf(p4d)); + + if (!p4d_present(p4d) || p4d_bad(p4d)) + return no_page_table(vma, flags, address); + + return follow_pud_mask(vma, address, p4dp, flags, page_mask); } /** @@ -385,69 +989,41 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma, * @vma: vm_area_struct mapping @address * @address: virtual address to look up * @flags: flags modifying lookup behaviour - * @ctx: contains dev_pagemap for %ZONE_DEVICE memory pinning and a - * pointer to output page_mask + * @page_mask: a pointer to output page_mask * * @flags can have FOLL_ flags set, defined in <linux/mm.h> * - * When getting pages from ZONE_DEVICE memory, the @ctx->pgmap caches - * the device's dev_pagemap metadata to avoid repeating expensive lookups. + * When getting an anonymous page and the caller has to trigger unsharing + * of a shared anonymous page first, -EMLINK is returned. The caller should + * trigger a fault with FAULT_FLAG_UNSHARE set. Note that unsharing is only + * relevant with FOLL_PIN and !FOLL_WRITE. * - * On output, the @ctx->page_mask is set according to the size of the page. + * On output, @page_mask is set according to the size of the page. * * Return: the mapped (struct page *), %NULL if no mapping exists, or * an error pointer if there is a mapping to something not represented * by a page descriptor (see also vm_normal_page()). */ -struct page *follow_page_mask(struct vm_area_struct *vma, +static struct page *follow_page_mask(struct vm_area_struct *vma, unsigned long address, unsigned int flags, - struct follow_page_context *ctx) + unsigned long *page_mask) { pgd_t *pgd; - struct page *page; struct mm_struct *mm = vma->vm_mm; + struct page *page; - ctx->page_mask = 0; - - /* make this handle hugepd */ - page = follow_huge_addr(mm, address, flags & FOLL_WRITE); - if (!IS_ERR(page)) { - BUG_ON(flags & FOLL_GET); - return page; - } + vma_pgtable_walk_begin(vma); + *page_mask = 0; pgd = pgd_offset(mm, address); if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd))) - return no_page_table(vma, flags); - - if (pgd_huge(*pgd)) { - page = follow_huge_pgd(mm, address, pgd, flags); - if (page) - return page; - return no_page_table(vma, flags); - } - if (is_hugepd(__hugepd(pgd_val(*pgd)))) { - page = follow_huge_pd(vma, address, - __hugepd(pgd_val(*pgd)), flags, - PGDIR_SHIFT); - if (page) - return page; - return no_page_table(vma, flags); - } + page = no_page_table(vma, flags, address); + else + page = follow_p4d_mask(vma, address, pgd, flags, page_mask); - return follow_p4d_mask(vma, address, pgd, flags, ctx); -} + vma_pgtable_walk_end(vma); -struct page *follow_page(struct vm_area_struct *vma, unsigned long address, - unsigned int foll_flags) -{ - struct follow_page_context ctx = { NULL }; - struct page *page; - - page = follow_page_mask(vma, address, foll_flags, &ctx); - if (ctx.pgmap) - put_dev_pagemap(ctx.pgmap); return page; } @@ -460,44 +1036,42 @@ static int get_gate_page(struct mm_struct *mm, unsigned long address, pud_t *pud; pmd_t *pmd; pte_t *pte; + pte_t entry; int ret = -EFAULT; /* user gate pages are read-only */ if (gup_flags & FOLL_WRITE) return -EFAULT; - if (address > TASK_SIZE) - pgd = pgd_offset_k(address); - else - pgd = pgd_offset_gate(mm, address); - BUG_ON(pgd_none(*pgd)); + pgd = pgd_offset(mm, address); + if (pgd_none(*pgd)) + return -EFAULT; p4d = p4d_offset(pgd, address); - BUG_ON(p4d_none(*p4d)); + if (p4d_none(*p4d)) + return -EFAULT; pud = pud_offset(p4d, address); - BUG_ON(pud_none(*pud)); + if (pud_none(*pud)) + return -EFAULT; pmd = pmd_offset(pud, address); if (!pmd_present(*pmd)) return -EFAULT; - VM_BUG_ON(pmd_trans_huge(*pmd)); pte = pte_offset_map(pmd, address); - if (pte_none(*pte)) + if (!pte) + return -EFAULT; + entry = ptep_get(pte); + if (pte_none(entry)) goto unmap; *vma = get_gate_vma(mm); if (!page) goto out; - *page = vm_normal_page(*vma, address, *pte); + *page = vm_normal_page(*vma, address, entry); if (!*page) { - if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(*pte))) - goto unmap; - *page = pte_page(*pte); - - /* - * This should never happen (a device public page in the gate - * area). - */ - if (is_device_public_page(*page)) + if ((gup_flags & FOLL_DUMP) || !is_zero_pfn(pte_pfn(entry))) goto unmap; + *page = pte_page(entry); } - get_page(*page); + ret = try_grab_folio(page_folio(*page), 1, gup_flags); + if (unlikely(ret)) + goto unmap; out: ret = 0; unmap: @@ -506,66 +1080,121 @@ unmap: } /* - * mmap_sem must be held on entry. If @nonblocking != NULL and - * *@flags does not include FOLL_NOWAIT, the mmap_sem may be released. - * If it is, *@nonblocking will be set to 0 and -EBUSY returned. + * mmap_lock must be held on entry. If @flags has FOLL_UNLOCKABLE but not + * FOLL_NOWAIT, the mmap_lock may be released. If it is, *@locked will be set + * to 0 and -EBUSY returned. */ -static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma, - unsigned long address, unsigned int *flags, int *nonblocking) +static int faultin_page(struct vm_area_struct *vma, + unsigned long address, unsigned int flags, bool unshare, + int *locked) { unsigned int fault_flags = 0; vm_fault_t ret; - /* mlock all present pages, but do not fault in new pages */ - if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) - return -ENOENT; - if (*flags & FOLL_WRITE) + if (flags & FOLL_NOFAULT) + return -EFAULT; + if (flags & FOLL_WRITE) fault_flags |= FAULT_FLAG_WRITE; - if (*flags & FOLL_REMOTE) + if (flags & FOLL_REMOTE) fault_flags |= FAULT_FLAG_REMOTE; - if (nonblocking) - fault_flags |= FAULT_FLAG_ALLOW_RETRY; - if (*flags & FOLL_NOWAIT) + if (flags & FOLL_UNLOCKABLE) { + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; + /* + * FAULT_FLAG_INTERRUPTIBLE is opt-in. GUP callers must set + * FOLL_INTERRUPTIBLE to enable FAULT_FLAG_INTERRUPTIBLE. + * That's because some callers may not be prepared to + * handle early exits caused by non-fatal signals. + */ + if (flags & FOLL_INTERRUPTIBLE) + fault_flags |= FAULT_FLAG_INTERRUPTIBLE; + } + if (flags & FOLL_NOWAIT) fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT; - if (*flags & FOLL_TRIED) { - VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_ALLOW_RETRY); + if (flags & FOLL_TRIED) { + /* + * Note: FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_TRIED + * can co-exist + */ fault_flags |= FAULT_FLAG_TRIED; } + if (unshare) { + fault_flags |= FAULT_FLAG_UNSHARE; + /* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */ + VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_WRITE); + } + + ret = handle_mm_fault(vma, address, fault_flags, NULL); + + if (ret & VM_FAULT_COMPLETED) { + /* + * With FAULT_FLAG_RETRY_NOWAIT we'll never release the + * mmap lock in the page fault handler. Sanity check this. + */ + WARN_ON_ONCE(fault_flags & FAULT_FLAG_RETRY_NOWAIT); + *locked = 0; + + /* + * We should do the same as VM_FAULT_RETRY, but let's not + * return -EBUSY since that's not reflecting the reality of + * what has happened - we've just fully completed a page + * fault, with the mmap lock released. Use -EAGAIN to show + * that we want to take the mmap lock _again_. + */ + return -EAGAIN; + } - ret = handle_mm_fault(vma, address, fault_flags); if (ret & VM_FAULT_ERROR) { - int err = vm_fault_to_errno(ret, *flags); + int err = vm_fault_to_errno(ret, flags); if (err) return err; BUG(); } - if (tsk) { - if (ret & VM_FAULT_MAJOR) - tsk->maj_flt++; - else - tsk->min_flt++; - } - if (ret & VM_FAULT_RETRY) { - if (nonblocking && !(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) - *nonblocking = 0; + if (!(fault_flags & FAULT_FLAG_RETRY_NOWAIT)) + *locked = 0; return -EBUSY; } + return 0; +} + +/* + * Writing to file-backed mappings which require folio dirty tracking using GUP + * is a fundamentally broken operation, as kernel write access to GUP mappings + * do not adhere to the semantics expected by a file system. + * + * Consider the following scenario:- + * + * 1. A folio is written to via GUP which write-faults the memory, notifying + * the file system and dirtying the folio. + * 2. Later, writeback is triggered, resulting in the folio being cleaned and + * the PTE being marked read-only. + * 3. The GUP caller writes to the folio, as it is mapped read/write via the + * direct mapping. + * 4. The GUP caller, now done with the page, unpins it and sets it dirty + * (though it does not have to). + * + * This results in both data being written to a folio without writenotify, and + * the folio being dirtied unexpectedly (if the caller decides to do so). + */ +static bool writable_file_mapping_allowed(struct vm_area_struct *vma, + unsigned long gup_flags) +{ /* - * The VM_FAULT_WRITE bit tells us that do_wp_page has broken COW when - * necessary, even if maybe_mkwrite decided not to set pte_write. We - * can thus safely do subsequent page lookups as if they were reads. - * But only do so when looping for pte_write is futile: in some cases - * userspace may also be wanting to write to the gotten user page, - * which a read fault here might prevent (a readonly page might get - * reCOWed by userspace write). + * If we aren't pinning then no problematic write can occur. A long term + * pin is the most egregious case so this is the case we disallow. */ - if ((ret & VM_FAULT_WRITE) && !(vma->vm_flags & VM_WRITE)) - *flags |= FOLL_COW; - return 0; + if ((gup_flags & (FOLL_PIN | FOLL_LONGTERM)) != + (FOLL_PIN | FOLL_LONGTERM)) + return true; + + /* + * If the VMA does not require dirty tracking then no problematic write + * can occur either. + */ + return !vma_needs_dirty_tracking(vma); } static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) @@ -573,15 +1202,29 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) vm_flags_t vm_flags = vma->vm_flags; int write = (gup_flags & FOLL_WRITE); int foreign = (gup_flags & FOLL_REMOTE); + bool vma_anon = vma_is_anonymous(vma); if (vm_flags & (VM_IO | VM_PFNMAP)) return -EFAULT; - if (gup_flags & FOLL_ANON && !vma_is_anonymous(vma)) + if ((gup_flags & FOLL_ANON) && !vma_anon) + return -EFAULT; + + if ((gup_flags & FOLL_LONGTERM) && vma_is_fsdax(vma)) + return -EOPNOTSUPP; + + if ((gup_flags & FOLL_SPLIT_PMD) && is_vm_hugetlb_page(vma)) + return -EOPNOTSUPP; + + if (vma_is_secretmem(vma)) return -EFAULT; if (write) { - if (!(vm_flags & VM_WRITE)) { + if (!vma_anon && + !writable_file_mapping_allowed(vma, gup_flags)) + return -EFAULT; + + if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; /* @@ -615,9 +1258,47 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) return 0; } +/* + * This is "vma_lookup()", but with a warning if we would have + * historically expanded the stack in the GUP code. + */ +static struct vm_area_struct *gup_vma_lookup(struct mm_struct *mm, + unsigned long addr) +{ +#ifdef CONFIG_STACK_GROWSUP + return vma_lookup(mm, addr); +#else + static volatile unsigned long next_warn; + struct vm_area_struct *vma; + unsigned long now, next; + + vma = find_vma(mm, addr); + if (!vma || (addr >= vma->vm_start)) + return vma; + + /* Only warn for half-way relevant accesses */ + if (!(vma->vm_flags & VM_GROWSDOWN)) + return NULL; + if (vma->vm_start - addr > 65536) + return NULL; + + /* Let's not warn more than once an hour.. */ + now = jiffies; next = next_warn; + if (next && time_before(now, next)) + return NULL; + next_warn = now + 60*60*HZ; + + /* Let people know things may have changed. */ + pr_warn("GUP no longer grows the stack in %s (%d): %lx-%lx (%lx)\n", + current->comm, task_pid_nr(current), + vma->vm_start, vma->vm_end, addr); + dump_stack(); + return NULL; +#endif +} + /** * __get_user_pages() - pin user pages in memory - * @tsk: task_struct of target task * @mm: mm_struct of target mm * @start: starting user address * @nr_pages: number of pages from start to pin @@ -625,17 +1306,20 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) * @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. Or NULL, if caller * only intends to ensure the pages are faulted in. - * @vmas: array of pointers to vmas corresponding to each page. - * Or NULL if the caller does not require them. - * @nonblocking: whether waiting for disk IO or mmap_sem contention + * @locked: whether we're still with the mmap_lock held + * + * Returns either number of pages pinned (which may be less than the + * number requested), or an error. Details about the return value: * - * Returns number of pages pinned. This may be fewer than the number - * requested. If nr_pages is 0 or negative, returns 0. If no pages - * were pinned, returns -errno. Each page returned must be released - * with a put_page() call when it is finished with. vmas will only - * remain valid while mmap_sem is held. + * -- If nr_pages is 0, returns 0. + * -- If nr_pages is >0, but no pages were pinned, returns -errno. + * -- If nr_pages is >0, and some pages were pinned, returns the number of + * pages pinned. Again, this may be less than nr_pages. + * -- 0 return value is possible when the fault would need to be retried. * - * Must be called with mmap_sem held. It may be released. See below. + * The caller is responsible for releasing returned @pages, via put_page(). + * + * Must be called with mmap_lock held. It may be released. See below. * * __get_user_pages walks a process's page tables and takes a reference to * each struct page that each user address corresponds to at a given @@ -645,7 +1329,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) * This does not guarantee that the page exists in the user mappings when * __get_user_pages returns, and there may even be a completely different * page there in some cases (eg. if mmapped pagecache has been invalidated - * and subsequently re faulted). However it does guarantee that the page + * and subsequently re-faulted). However it does guarantee that the page * won't be freed completely. And mostly callers simply care that the page * contains data that was valid *at some point in time*. Typically, an IO * or similar operation cannot guarantee anything stronger anyway because @@ -656,71 +1340,77 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) * appropriate) must be called after the page is finished with, and * before put_page is called. * - * If @nonblocking != NULL, __get_user_pages will not wait for disk IO - * or mmap_sem contention, and if waiting is needed to pin all pages, - * *@nonblocking will be set to 0. Further, if @gup_flags does not - * include FOLL_NOWAIT, the mmap_sem will be released via up_read() in - * this case. + * If FOLL_UNLOCKABLE is set without FOLL_NOWAIT then the mmap_lock may + * be released. If this happens *@locked will be set to 0 on return. * - * A caller using such a combination of @nonblocking and @gup_flags - * must therefore hold the mmap_sem for reading only, and recognize - * when it's been released. Otherwise, it must be held for either - * reading or writing and will not be released. + * A caller using such a combination of @gup_flags must therefore hold the + * mmap_lock for reading only, and recognize when it's been released. Otherwise, + * it must be held for either reading or writing and will not be released. * * In most cases, get_user_pages or get_user_pages_fast should be used * instead of __get_user_pages. __get_user_pages should be used only if * you need some special @gup_flags. */ -static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, +static long __get_user_pages(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, unsigned int gup_flags, struct page **pages, - struct vm_area_struct **vmas, int *nonblocking) + int *locked) { long ret = 0, i = 0; struct vm_area_struct *vma = NULL; - struct follow_page_context ctx = { NULL }; + unsigned long page_mask = 0; if (!nr_pages) return 0; - VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); + start = untagged_addr_remote(mm, start); - /* - * If FOLL_FORCE is set then do not force a full fault as the hinting - * fault information is unrelated to the reference behaviour of a task - * using the address space - */ - if (!(gup_flags & FOLL_FORCE)) - gup_flags |= FOLL_NUMA; + VM_WARN_ON_ONCE(!!pages != !!(gup_flags & (FOLL_GET | FOLL_PIN))); + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + VM_WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET)); do { struct page *page; - unsigned int foll_flags = gup_flags; unsigned int page_increm; /* first iteration or cross vma bound */ if (!vma || start >= vma->vm_end) { - vma = find_extend_vma(mm, start); + /* + * MADV_POPULATE_(READ|WRITE) wants to handle VMA + * lookups+error reporting differently. + */ + if (gup_flags & FOLL_MADV_POPULATE) { + vma = vma_lookup(mm, start); + if (!vma) { + ret = -ENOMEM; + goto out; + } + if (check_vma_flags(vma, gup_flags)) { + ret = -EINVAL; + goto out; + } + goto retry; + } + vma = gup_vma_lookup(mm, start); if (!vma && in_gate_area(mm, start)) { ret = get_gate_page(mm, start & PAGE_MASK, gup_flags, &vma, - pages ? &pages[i] : NULL); + pages ? &page : NULL); if (ret) goto out; - ctx.page_mask = 0; + page_mask = 0; goto next_page; } - if (!vma || check_vma_flags(vma, gup_flags)) { + if (!vma) { ret = -EFAULT; goto out; } - if (is_vm_hugetlb_page(vma)) { - i = follow_hugetlb_page(mm, vma, pages, vmas, - &start, &nr_pages, i, - gup_flags, nonblocking); - continue; - } + ret = check_vma_flags(vma, gup_flags); + if (ret) + goto out; } retry: /* @@ -728,60 +1418,94 @@ retry: * potentially allocating memory. */ if (fatal_signal_pending(current)) { - ret = -ERESTARTSYS; + ret = -EINTR; goto out; } cond_resched(); - page = follow_page_mask(vma, start, foll_flags, &ctx); - if (!page) { - ret = faultin_page(tsk, vma, start, &foll_flags, - nonblocking); + page = follow_page_mask(vma, start, gup_flags, &page_mask); + if (!page || PTR_ERR(page) == -EMLINK) { + ret = faultin_page(vma, start, gup_flags, + PTR_ERR(page) == -EMLINK, locked); switch (ret) { case 0: goto retry; case -EBUSY: + case -EAGAIN: ret = 0; - /* FALLTHRU */ + fallthrough; case -EFAULT: case -ENOMEM: case -EHWPOISON: goto out; - case -ENOENT: - goto next_page; } BUG(); } else if (PTR_ERR(page) == -EEXIST) { /* * Proper page table entry exists, but no corresponding - * struct page. + * struct page. If the caller expects **pages to be + * filled in, bail out now, because that can't be done + * for this page. */ - goto next_page; + if (pages) { + ret = PTR_ERR(page); + goto out; + } } else if (IS_ERR(page)) { ret = PTR_ERR(page); goto out; } - if (pages) { - pages[i] = page; - flush_anon_page(vma, page, start); - flush_dcache_page(page); - ctx.page_mask = 0; - } next_page: - if (vmas) { - vmas[i] = vma; - ctx.page_mask = 0; - } - page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); + page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask); if (page_increm > nr_pages) page_increm = nr_pages; + + if (pages) { + struct page *subpage; + unsigned int j; + + /* + * This must be a large folio (and doesn't need to + * be the whole folio; it can be part of it), do + * the refcount work for all the subpages too. + * + * NOTE: here the page may not be the head page + * e.g. when start addr is not thp-size aligned. + * try_grab_folio() should have taken care of tail + * pages. + */ + if (page_increm > 1) { + struct folio *folio = page_folio(page); + + /* + * Since we already hold refcount on the + * large folio, this should never fail. + */ + if (try_grab_folio(folio, page_increm - 1, + gup_flags)) { + /* + * Release the 1st page ref if the + * folio is problematic, fail hard. + */ + gup_put_folio(folio, 1, gup_flags); + ret = -EFAULT; + goto out; + } + } + + for (j = 0; j < page_increm; j++) { + subpage = page + j; + pages[i + j] = subpage; + flush_anon_page(vma, subpage, start + j * PAGE_SIZE); + flush_dcache_page(subpage); + } + } + i += page_increm; start += page_increm * PAGE_SIZE; nr_pages -= page_increm; } while (nr_pages); out: - if (ctx.pgmap) - put_dev_pagemap(ctx.pgmap); return i ? i : ret; } @@ -808,15 +1532,14 @@ static bool vma_permits_fault(struct vm_area_struct *vma, return true; } -/* +/** * fixup_user_fault() - manually resolve a user page fault - * @tsk: the task_struct to use for page fault accounting, or - * NULL if faults are not to be recorded. * @mm: mm_struct of target mm * @address: user address * @fault_flags:flags to pass down to handle_mm_fault() - * @unlocked: did we unlock the mmap_sem while retrying, maybe NULL if caller - * does not allow retry + * @unlocked: did we unlock the mmap_lock while retrying, maybe NULL if caller + * does not allow retry. If NULL, the caller must guarantee + * that fault_flags does not contain FAULT_FLAG_ALLOW_RETRY. * * This is meant to be called in the specific scenario where for locking reasons * we try to access user memory in atomic context (within a pagefault_disable() @@ -835,29 +1558,46 @@ static bool vma_permits_fault(struct vm_area_struct *vma, * such architectures, gup() will not be enough to make a subsequent access * succeed. * - * This function will not return with an unlocked mmap_sem. So it has not the - * same semantics wrt the @mm->mmap_sem as does filemap_fault(). + * This function will not return with an unlocked mmap_lock. So it has not the + * same semantics wrt the @mm->mmap_lock as does filemap_fault(). */ -int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, +int fixup_user_fault(struct mm_struct *mm, unsigned long address, unsigned int fault_flags, bool *unlocked) { struct vm_area_struct *vma; - vm_fault_t ret, major = 0; + vm_fault_t ret; + + address = untagged_addr_remote(mm, address); if (unlocked) - fault_flags |= FAULT_FLAG_ALLOW_RETRY; + fault_flags |= FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; retry: - vma = find_extend_vma(mm, address); - if (!vma || address < vma->vm_start) + vma = gup_vma_lookup(mm, address); + if (!vma) return -EFAULT; if (!vma_permits_fault(vma, fault_flags)) return -EFAULT; - ret = handle_mm_fault(vma, address, fault_flags); - major |= ret & VM_FAULT_MAJOR; + if ((fault_flags & FAULT_FLAG_KILLABLE) && + fatal_signal_pending(current)) + return -EINTR; + + ret = handle_mm_fault(vma, address, fault_flags, NULL); + + if (ret & VM_FAULT_COMPLETED) { + /* + * NOTE: it's a pity that we need to retake the lock here + * to pair with the unlock() in the callers. Ideally we + * could tell the callers so they do not need to unlock. + */ + mmap_read_lock(mm); + *unlocked = true; + return 0; + } + if (ret & VM_FAULT_ERROR) { int err = vm_fault_to_errno(ret, 0); @@ -867,65 +1607,98 @@ retry: } if (ret & VM_FAULT_RETRY) { - down_read(&mm->mmap_sem); - if (!(fault_flags & FAULT_FLAG_TRIED)) { - *unlocked = true; - fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; - fault_flags |= FAULT_FLAG_TRIED; - goto retry; - } + mmap_read_lock(mm); + *unlocked = true; + fault_flags |= FAULT_FLAG_TRIED; + goto retry; } - if (tsk) { - if (major) - tsk->maj_flt++; - else - tsk->min_flt++; - } return 0; } EXPORT_SYMBOL_GPL(fixup_user_fault); -static __always_inline long __get_user_pages_locked(struct task_struct *tsk, - struct mm_struct *mm, +/* + * GUP always responds to fatal signals. When FOLL_INTERRUPTIBLE is + * specified, it'll also respond to generic signals. The caller of GUP + * that has FOLL_INTERRUPTIBLE should take care of the GUP interruption. + */ +static bool gup_signal_pending(unsigned int flags) +{ + if (fatal_signal_pending(current)) + return true; + + if (!(flags & FOLL_INTERRUPTIBLE)) + return false; + + return signal_pending(current); +} + +/* + * Locking: (*locked == 1) means that the mmap_lock has already been acquired by + * the caller. This function may drop the mmap_lock. If it does so, then it will + * set (*locked = 0). + * + * (*locked == 0) means that the caller expects this function to acquire and + * drop the mmap_lock. Therefore, the value of *locked will still be zero when + * the function returns, even though it may have changed temporarily during + * function execution. + * + * Please note that this function, unlike __get_user_pages(), will not return 0 + * for nr_pages > 0, unless FOLL_NOWAIT is used. + */ +static __always_inline long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, unsigned long nr_pages, struct page **pages, - struct vm_area_struct **vmas, int *locked, unsigned int flags) { long ret, pages_done; - bool lock_dropped; + bool must_unlock = false; - if (locked) { - /* if VM_FAULT_RETRY can be returned, vmas become invalid */ - BUG_ON(vmas); - /* check caller initialized locked */ - BUG_ON(*locked != 1); + if (!nr_pages) + return 0; + + /* + * The internal caller expects GUP to manage the lock internally and the + * lock must be released when this returns. + */ + if (!*locked) { + if (mmap_read_lock_killable(mm)) + return -EAGAIN; + must_unlock = true; + *locked = 1; } + else + mmap_assert_locked(mm); + + if (flags & FOLL_PIN) + mm_set_has_pinned_flag(mm); - if (pages) + /* + * FOLL_PIN and FOLL_GET are mutually exclusive. Traditional behavior + * is to set FOLL_GET if the caller wants pages[] filled in (but has + * carelessly failed to specify FOLL_GET), so keep doing that, but only + * for FOLL_GET, not for the newer FOLL_PIN. + * + * FOLL_PIN always expects pages to be non-null, but no need to assert + * that here, as any failures will be obvious enough. + */ + if (pages && !(flags & FOLL_PIN)) flags |= FOLL_GET; pages_done = 0; - lock_dropped = false; for (;;) { - ret = __get_user_pages(tsk, mm, start, nr_pages, flags, pages, - vmas, locked); - if (!locked) + ret = __get_user_pages(mm, start, nr_pages, flags, pages, + locked); + if (!(flags & FOLL_UNLOCKABLE)) { /* VM_FAULT_RETRY couldn't trigger, bypass */ - return ret; - - /* VM_FAULT_RETRY cannot return errors */ - if (!*locked) { - BUG_ON(ret < 0); - BUG_ON(ret >= nr_pages); + pages_done = ret; + break; } - if (!pages) - /* If it's a prefault don't insist harder */ - return ret; + /* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */ + VM_WARN_ON_ONCE(!*locked && (ret < 0 || ret >= nr_pages)); if (ret > 0) { nr_pages -= ret; @@ -942,22 +1715,49 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, pages_done = ret; break; } - /* VM_FAULT_RETRY triggered, so seek to the faulting offset */ - pages += ret; + /* + * VM_FAULT_RETRY triggered, so seek to the faulting offset. + * For the prefault case (!pages) we only update counts. + */ + if (likely(pages)) + pages += ret; start += ret << PAGE_SHIFT; + /* The lock was temporarily dropped, so we must unlock later */ + must_unlock = true; + +retry: /* * Repeat on the address that fired VM_FAULT_RETRY - * without FAULT_FLAG_ALLOW_RETRY but with - * FAULT_FLAG_TRIED. + * with both FAULT_FLAG_ALLOW_RETRY and + * FAULT_FLAG_TRIED. Note that GUP can be interrupted + * by fatal signals of even common signals, depending on + * the caller's request. So we need to check it before we + * start trying again otherwise it can loop forever. */ + if (gup_signal_pending(flags)) { + if (!pages_done) + pages_done = -EINTR; + break; + } + + ret = mmap_read_lock_killable(mm); + if (ret) { + if (!pages_done) + pages_done = ret; + break; + } + *locked = 1; - lock_dropped = true; - down_read(&mm->mmap_sem); - ret = __get_user_pages(tsk, mm, start, 1, flags | FOLL_TRIED, - pages, NULL, NULL); + ret = __get_user_pages(mm, start, 1, flags | FOLL_TRIED, + pages, locked); + if (!*locked) { + /* Continue to retry until we succeeded */ + VM_WARN_ON_ONCE(ret != 0); + goto retry; + } if (ret != 1) { - BUG_ON(ret > 1); + VM_WARN_ON_ONCE(ret > 1); if (!pages_done) pages_done = ret; break; @@ -966,286 +1766,153 @@ static __always_inline long __get_user_pages_locked(struct task_struct *tsk, pages_done++; if (!nr_pages) break; - pages++; + if (likely(pages)) + pages++; start += PAGE_SIZE; } - if (lock_dropped && *locked) { + if (must_unlock && *locked) { /* - * We must let the caller know we temporarily dropped the lock - * and so the critical section protected by it was lost. + * We either temporarily dropped the lock, or the caller + * requested that we both acquire and drop the lock. Either way, + * we must now unlock, and notify the caller of that state. */ - up_read(&mm->mmap_sem); + mmap_read_unlock(mm); *locked = 0; } - return pages_done; -} - -/* - * We can leverage the VM_FAULT_RETRY functionality in the page fault - * paths better by using either get_user_pages_locked() or - * get_user_pages_unlocked(). - * - * get_user_pages_locked() is suitable to replace the form: - * - * down_read(&mm->mmap_sem); - * do_something() - * get_user_pages(tsk, mm, ..., pages, NULL); - * up_read(&mm->mmap_sem); - * - * to: - * - * int locked = 1; - * down_read(&mm->mmap_sem); - * do_something() - * get_user_pages_locked(tsk, mm, ..., pages, &locked); - * if (locked) - * up_read(&mm->mmap_sem); - */ -long get_user_pages_locked(unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - int *locked) -{ - return __get_user_pages_locked(current, current->mm, start, nr_pages, - pages, NULL, locked, - gup_flags | FOLL_TOUCH); -} -EXPORT_SYMBOL(get_user_pages_locked); - -/* - * get_user_pages_unlocked() is suitable to replace the form: - * - * down_read(&mm->mmap_sem); - * get_user_pages(tsk, mm, ..., pages, NULL); - * up_read(&mm->mmap_sem); - * - * with: - * - * get_user_pages_unlocked(tsk, mm, ..., pages); - * - * It is functionally equivalent to get_user_pages_fast so - * get_user_pages_fast should be used instead if specific gup_flags - * (e.g. FOLL_FORCE) are not required. - */ -long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, - struct page **pages, unsigned int gup_flags) -{ - struct mm_struct *mm = current->mm; - int locked = 1; - long ret; - - down_read(&mm->mmap_sem); - ret = __get_user_pages_locked(current, mm, start, nr_pages, pages, NULL, - &locked, gup_flags | FOLL_TOUCH); - if (locked) - up_read(&mm->mmap_sem); - return ret; -} -EXPORT_SYMBOL(get_user_pages_unlocked); - -/* - * get_user_pages_remote() - pin user pages in memory - * @tsk: the task_struct to use for page fault accounting, or - * NULL if faults are not to be recorded. - * @mm: mm_struct of target mm - * @start: starting user address - * @nr_pages: number of pages from start to pin - * @gup_flags: flags modifying lookup behaviour - * @pages: array that receives pointers to the pages pinned. - * Should be at least nr_pages long. Or NULL, if caller - * only intends to ensure the pages are faulted in. - * @vmas: array of pointers to vmas corresponding to each page. - * Or NULL if the caller does not require them. - * @locked: pointer to lock flag indicating whether lock is held and - * subsequently whether VM_FAULT_RETRY functionality can be - * utilised. Lock must initially be held. - * - * Returns number of pages pinned. This may be fewer than the number - * requested. If nr_pages is 0 or negative, returns 0. If no pages - * were pinned, returns -errno. Each page returned must be released - * with a put_page() call when it is finished with. vmas will only - * remain valid while mmap_sem is held. - * - * Must be called with mmap_sem held for read or write. - * - * get_user_pages walks a process's page tables and takes a reference to - * each struct page that each user address corresponds to at a given - * instant. That is, it takes the page that would be accessed if a user - * thread accesses the given user virtual address at that instant. - * - * This does not guarantee that the page exists in the user mappings when - * get_user_pages returns, and there may even be a completely different - * page there in some cases (eg. if mmapped pagecache has been invalidated - * and subsequently re faulted). However it does guarantee that the page - * won't be freed completely. And mostly callers simply care that the page - * contains data that was valid *at some point in time*. Typically, an IO - * or similar operation cannot guarantee anything stronger anyway because - * locks can't be held over the syscall boundary. - * - * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page - * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must - * be called after the page is finished with, and before put_page is called. - * - * get_user_pages is typically used for fewer-copy IO operations, to get a - * handle on the memory by some means other than accesses via the user virtual - * addresses. The pages may be submitted for DMA to devices or accessed via - * their kernel linear mapping (via the kmap APIs). Care should be taken to - * use the correct cache flushing APIs. - * - * See also get_user_pages_fast, for performance critical applications. - * - * get_user_pages should be phased out in favor of - * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing - * should use get_user_pages because it cannot pass - * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. - */ -long get_user_pages_remote(struct task_struct *tsk, struct mm_struct *mm, - unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - struct vm_area_struct **vmas, int *locked) -{ - return __get_user_pages_locked(tsk, mm, start, nr_pages, pages, vmas, - locked, - gup_flags | FOLL_TOUCH | FOLL_REMOTE); -} -EXPORT_SYMBOL(get_user_pages_remote); - -/* - * This is the same as get_user_pages_remote(), just with a - * less-flexible calling convention where we assume that the task - * and mm being operated on are the current task's and don't allow - * passing of a locked parameter. We also obviously don't pass - * FOLL_REMOTE in here. - */ -long get_user_pages(unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - struct vm_area_struct **vmas) -{ - return __get_user_pages_locked(current, current->mm, start, nr_pages, - pages, vmas, NULL, - gup_flags | FOLL_TOUCH); -} -EXPORT_SYMBOL(get_user_pages); - -#ifdef CONFIG_FS_DAX -/* - * This is the same as get_user_pages() in that it assumes we are - * operating on the current task's mm, but it goes further to validate - * that the vmas associated with the address range are suitable for - * longterm elevated page reference counts. For example, filesystem-dax - * mappings are subject to the lifetime enforced by the filesystem and - * we need guarantees that longterm users like RDMA and V4L2 only - * establish mappings that have a kernel enforced revocation mechanism. - * - * "longterm" == userspace controlled elevated page count lifetime. - * Contrast this to iov_iter_get_pages() usages which are transient. - */ -long get_user_pages_longterm(unsigned long start, unsigned long nr_pages, - unsigned int gup_flags, struct page **pages, - struct vm_area_struct **vmas_arg) -{ - struct vm_area_struct **vmas = vmas_arg; - struct vm_area_struct *vma_prev = NULL; - long rc, i; - - if (!pages) - return -EINVAL; - - if (!vmas) { - vmas = kcalloc(nr_pages, sizeof(struct vm_area_struct *), - GFP_KERNEL); - if (!vmas) - return -ENOMEM; - } - - rc = get_user_pages(start, nr_pages, gup_flags, pages, vmas); - - for (i = 0; i < rc; i++) { - struct vm_area_struct *vma = vmas[i]; - - if (vma == vma_prev) - continue; - - vma_prev = vma; - - if (vma_is_fsdax(vma)) - break; - } /* - * Either get_user_pages() failed, or the vma validation - * succeeded, in either case we don't need to put_page() before - * returning. + * Failing to pin anything implies something has gone wrong (except when + * FOLL_NOWAIT is specified). */ - if (i >= rc) - goto out; + if (WARN_ON_ONCE(pages_done == 0 && !(flags & FOLL_NOWAIT))) + return -EFAULT; - for (i = 0; i < rc; i++) - put_page(pages[i]); - rc = -EOPNOTSUPP; -out: - if (vmas != vmas_arg) - kfree(vmas); - return rc; + return pages_done; } -EXPORT_SYMBOL(get_user_pages_longterm); -#endif /* CONFIG_FS_DAX */ /** * populate_vma_page_range() - populate a range of pages in the vma. * @vma: target vma * @start: start address * @end: end address - * @nonblocking: + * @locked: whether the mmap_lock is still held * * This takes care of mlocking the pages too if VM_LOCKED is set. * - * return 0 on success, negative error code on error. + * Return either number of pages pinned in the vma, or a negative error + * code on error. * - * vma->vm_mm->mmap_sem must be held. + * vma->vm_mm->mmap_lock must be held. * - * If @nonblocking is NULL, it may be held for read or write and will + * If @locked is NULL, it may be held for read or write and will * be unperturbed. * - * If @nonblocking is non-NULL, it must held for read only and may be - * released. If it's released, *@nonblocking will be set to 0. + * If @locked is non-NULL, it must held for read only and may be + * released. If it's released, *@locked will be set to 0. */ long populate_vma_page_range(struct vm_area_struct *vma, - unsigned long start, unsigned long end, int *nonblocking) + unsigned long start, unsigned long end, int *locked) { struct mm_struct *mm = vma->vm_mm; unsigned long nr_pages = (end - start) / PAGE_SIZE; + int local_locked = 1; int gup_flags; + long ret; - VM_BUG_ON(start & ~PAGE_MASK); - VM_BUG_ON(end & ~PAGE_MASK); - VM_BUG_ON_VMA(start < vma->vm_start, vma); - VM_BUG_ON_VMA(end > vma->vm_end, vma); - VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_sem), mm); + VM_WARN_ON_ONCE(!PAGE_ALIGNED(start)); + VM_WARN_ON_ONCE(!PAGE_ALIGNED(end)); + VM_WARN_ON_ONCE_VMA(start < vma->vm_start, vma); + VM_WARN_ON_ONCE_VMA(end > vma->vm_end, vma); + mmap_assert_locked(mm); - gup_flags = FOLL_TOUCH | FOLL_POPULATE | FOLL_MLOCK; + /* + * Rightly or wrongly, the VM_LOCKONFAULT case has never used + * faultin_page() to break COW, so it has no work to do here. + */ if (vma->vm_flags & VM_LOCKONFAULT) - gup_flags &= ~FOLL_POPULATE; + return nr_pages; + + /* ... similarly, we've never faulted in PROT_NONE pages */ + if (!vma_is_accessible(vma)) + return -EFAULT; + + gup_flags = FOLL_TOUCH; /* * We want to touch writable mappings with a write fault in order * to break COW, except for shared mappings because these don't COW * and we would not want to dirty them for nothing. + * + * Otherwise, do a read fault, and use FOLL_FORCE in case it's not + * readable (ie write-only or executable). */ if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE) gup_flags |= FOLL_WRITE; - - /* - * We want mlock to succeed for regions that have any permissions - * other than PROT_NONE. - */ - if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) + else gup_flags |= FOLL_FORCE; + if (locked) + gup_flags |= FOLL_UNLOCKABLE; + /* * We made sure addr is within a VMA, so the following will * not result in a stack expansion that recurses back here. */ - return __get_user_pages(current, mm, start, nr_pages, gup_flags, - NULL, NULL, nonblocking); + ret = __get_user_pages(mm, start, nr_pages, gup_flags, + NULL, locked ? locked : &local_locked); + lru_add_drain(); + return ret; +} + +/* + * faultin_page_range() - populate (prefault) page tables inside the + * given range readable/writable + * + * This takes care of mlocking the pages, too, if VM_LOCKED is set. + * + * @mm: the mm to populate page tables in + * @start: start address + * @end: end address + * @write: whether to prefault readable or writable + * @locked: whether the mmap_lock is still held + * + * Returns either number of processed pages in the MM, or a negative error + * code on error (see __get_user_pages()). Note that this function reports + * errors related to VMAs, such as incompatible mappings, as expected by + * MADV_POPULATE_(READ|WRITE). + * + * The range must be page-aligned. + * + * mm->mmap_lock must be held. If it's released, *@locked will be set to 0. + */ +long faultin_page_range(struct mm_struct *mm, unsigned long start, + unsigned long end, bool write, int *locked) +{ + unsigned long nr_pages = (end - start) / PAGE_SIZE; + int gup_flags; + long ret; + + VM_WARN_ON_ONCE(!PAGE_ALIGNED(start)); + VM_WARN_ON_ONCE(!PAGE_ALIGNED(end)); + mmap_assert_locked(mm); + + /* + * FOLL_TOUCH: Mark page accessed and thereby young; will also mark + * the page dirty with FOLL_WRITE -- which doesn't make a + * difference with !FOLL_FORCE, because the page is writable + * in the page table. + * FOLL_HWPOISON: Return -EHWPOISON instead of -EFAULT when we hit + * a poisoned page. + * !FOLL_FORCE: Require proper access permissions. + */ + gup_flags = FOLL_TOUCH | FOLL_HWPOISON | FOLL_UNLOCKABLE | + FOLL_MADV_POPULATE; + if (write) + gup_flags |= FOLL_WRITE; + + ret = __get_user_pages_locked(mm, start, nr_pages, NULL, locked, + gup_flags); + lru_add_drain(); + return ret; } /* @@ -1253,7 +1920,7 @@ long populate_vma_page_range(struct vm_area_struct *vma, * * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap * flags. VMAs must be already marked with the desired vm_flags, and - * mmap_sem must not be held. + * mmap_lock must not be held. */ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) { @@ -1272,11 +1939,12 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) */ if (!locked) { locked = 1; - down_read(&mm->mmap_sem); - vma = find_vma(mm, nstart); + mmap_read_lock(mm); + vma = find_vma_intersection(mm, nstart, end); } else if (nstart >= vma->vm_end) - vma = vma->vm_next; - if (!vma || vma->vm_start >= end) + vma = find_vma_intersection(mm, vma->vm_end, end); + + if (!vma) break; /* * Set [nstart; nend) to intersection of desired address @@ -1304,13 +1972,206 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) ret = 0; } if (locked) - up_read(&mm->mmap_sem); + mmap_read_unlock(mm); return ret; /* 0 or negative error code */ } +#else /* CONFIG_MMU */ +static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, + unsigned long nr_pages, struct page **pages, + int *locked, unsigned int foll_flags) +{ + struct vm_area_struct *vma; + bool must_unlock = false; + vm_flags_t vm_flags; + long i; + + if (!nr_pages) + return 0; + + /* + * The internal caller expects GUP to manage the lock internally and the + * lock must be released when this returns. + */ + if (!*locked) { + if (mmap_read_lock_killable(mm)) + return -EAGAIN; + must_unlock = true; + *locked = 1; + } + + /* calculate required read or write permissions. + * If FOLL_FORCE is set, we only require the "MAY" flags. + */ + vm_flags = (foll_flags & FOLL_WRITE) ? + (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD); + vm_flags &= (foll_flags & FOLL_FORCE) ? + (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE); + + for (i = 0; i < nr_pages; i++) { + vma = find_vma(mm, start); + if (!vma) + break; + + /* protect what we can, including chardevs */ + if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) || + !(vm_flags & vma->vm_flags)) + break; + + if (pages) { + pages[i] = virt_to_page((void *)start); + if (pages[i]) + get_page(pages[i]); + } + + start = (start + PAGE_SIZE) & PAGE_MASK; + } + + if (must_unlock && *locked) { + mmap_read_unlock(mm); + *locked = 0; + } + + return i ? : -EFAULT; +} +#endif /* !CONFIG_MMU */ + +/** + * fault_in_writeable - fault in userspace address range for writing + * @uaddr: start of address range + * @size: size of address range + * + * Returns the number of bytes not faulted in (like copy_to_user() and + * copy_from_user()). + */ +size_t fault_in_writeable(char __user *uaddr, size_t size) +{ + const unsigned long start = (unsigned long)uaddr; + const unsigned long end = start + size; + unsigned long cur; + + if (unlikely(size == 0)) + return 0; + if (!user_write_access_begin(uaddr, size)) + return size; + + /* Stop once we overflow to 0. */ + for (cur = start; cur && cur < end; cur = PAGE_ALIGN_DOWN(cur + PAGE_SIZE)) + unsafe_put_user(0, (char __user *)cur, out); +out: + user_write_access_end(); + if (size > cur - start) + return size - (cur - start); + return 0; +} +EXPORT_SYMBOL(fault_in_writeable); + +/** + * fault_in_subpage_writeable - fault in an address range for writing + * @uaddr: start of address range + * @size: size of address range + * + * Fault in a user address range for writing while checking for permissions at + * sub-page granularity (e.g. arm64 MTE). This function should be used when + * the caller cannot guarantee forward progress of a copy_to_user() loop. + * + * Returns the number of bytes not faulted in (like copy_to_user() and + * copy_from_user()). + */ +size_t fault_in_subpage_writeable(char __user *uaddr, size_t size) +{ + size_t faulted_in; + + /* + * Attempt faulting in at page granularity first for page table + * permission checking. The arch-specific probe_subpage_writeable() + * functions may not check for this. + */ + faulted_in = size - fault_in_writeable(uaddr, size); + if (faulted_in) + faulted_in -= probe_subpage_writeable(uaddr, faulted_in); + + return size - faulted_in; +} +EXPORT_SYMBOL(fault_in_subpage_writeable); + +/* + * fault_in_safe_writeable - fault in an address range for writing + * @uaddr: start of address range + * @size: length of address range + * + * Faults in an address range for writing. This is primarily useful when we + * already know that some or all of the pages in the address range aren't in + * memory. + * + * Unlike fault_in_writeable(), this function is non-destructive. + * + * Note that we don't pin or otherwise hold the pages referenced that we fault + * in. There's no guarantee that they'll stay in memory for any duration of + * time. + * + * Returns the number of bytes not faulted in, like copy_to_user() and + * copy_from_user(). + */ +size_t fault_in_safe_writeable(const char __user *uaddr, size_t size) +{ + const unsigned long start = (unsigned long)uaddr; + const unsigned long end = start + size; + unsigned long cur; + struct mm_struct *mm = current->mm; + bool unlocked = false; + + if (unlikely(size == 0)) + return 0; + + mmap_read_lock(mm); + /* Stop once we overflow to 0. */ + for (cur = start; cur && cur < end; cur = PAGE_ALIGN_DOWN(cur + PAGE_SIZE)) + if (fixup_user_fault(mm, cur, FAULT_FLAG_WRITE, &unlocked)) + break; + mmap_read_unlock(mm); + + if (size > cur - start) + return size - (cur - start); + return 0; +} +EXPORT_SYMBOL(fault_in_safe_writeable); + +/** + * fault_in_readable - fault in userspace address range for reading + * @uaddr: start of user address range + * @size: size of user address range + * + * Returns the number of bytes not faulted in (like copy_to_user() and + * copy_from_user()). + */ +size_t fault_in_readable(const char __user *uaddr, size_t size) +{ + const unsigned long start = (unsigned long)uaddr; + const unsigned long end = start + size; + unsigned long cur; + volatile char c; + + if (unlikely(size == 0)) + return 0; + if (!user_read_access_begin(uaddr, size)) + return size; + + /* Stop once we overflow to 0. */ + for (cur = start; cur && cur < end; cur = PAGE_ALIGN_DOWN(cur + PAGE_SIZE)) + unsafe_get_user(c, (const char __user *)cur, out); +out: + user_read_access_end(); + (void)c; + if (size > cur - start) + return size - (cur - start); + return 0; +} +EXPORT_SYMBOL(fault_in_readable); /** * get_dump_page() - pin user page in memory while writing it to core dump * @addr: user address + * @locked: a pointer to an int denoting whether the mmap sem is held * * Returns struct page pointer of user page pinned for dump, * to be freed afterwards by put_page(). @@ -1318,27 +2179,512 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors) * Returns NULL on any kind of failure - a hole must then be inserted into * the corefile, to preserve alignment with its headers; and also returns * NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found - - * allowing a hole to be left in the corefile to save diskspace. + * allowing a hole to be left in the corefile to save disk space. * - * Called without mmap_sem, but after all other threads have been killed. + * Called without mmap_lock (takes and releases the mmap_lock by itself). */ #ifdef CONFIG_ELF_CORE -struct page *get_dump_page(unsigned long addr) +struct page *get_dump_page(unsigned long addr, int *locked) { - struct vm_area_struct *vma; struct page *page; + int ret; - if (__get_user_pages(current, current->mm, addr, 1, - FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma, - NULL) < 1) - return NULL; - flush_cache_page(vma, addr, page_to_pfn(page)); - return page; + ret = __get_user_pages_locked(current->mm, addr, 1, &page, locked, + FOLL_FORCE | FOLL_DUMP | FOLL_GET); + return (ret == 1) ? page : NULL; } #endif /* CONFIG_ELF_CORE */ +#ifdef CONFIG_MIGRATION + +/* + * An array of either pages or folios ("pofs"). Although it may seem tempting to + * avoid this complication, by simply interpreting a list of folios as a list of + * pages, that approach won't work in the longer term, because eventually the + * layouts of struct page and struct folio will become completely different. + * Furthermore, this pof approach avoids excessive page_folio() calls. + */ +struct pages_or_folios { + union { + struct page **pages; + struct folio **folios; + void **entries; + }; + bool has_folios; + long nr_entries; +}; + +static struct folio *pofs_get_folio(struct pages_or_folios *pofs, long i) +{ + if (pofs->has_folios) + return pofs->folios[i]; + return page_folio(pofs->pages[i]); +} + +static void pofs_clear_entry(struct pages_or_folios *pofs, long i) +{ + pofs->entries[i] = NULL; +} + +static void pofs_unpin(struct pages_or_folios *pofs) +{ + if (pofs->has_folios) + unpin_folios(pofs->folios, pofs->nr_entries); + else + unpin_user_pages(pofs->pages, pofs->nr_entries); +} + +static struct folio *pofs_next_folio(struct folio *folio, + struct pages_or_folios *pofs, long *index_ptr) +{ + long i = *index_ptr + 1; + + if (!pofs->has_folios && folio_test_large(folio)) { + const unsigned long start_pfn = folio_pfn(folio); + const unsigned long end_pfn = start_pfn + folio_nr_pages(folio); + + for (; i < pofs->nr_entries; i++) { + unsigned long pfn = page_to_pfn(pofs->pages[i]); + + /* Is this page part of this folio? */ + if (pfn < start_pfn || pfn >= end_pfn) + break; + } + } + + if (unlikely(i == pofs->nr_entries)) + return NULL; + *index_ptr = i; + + return pofs_get_folio(pofs, i); +} + +/* + * Returns the number of collected folios. Return value is always >= 0. + */ +static unsigned long collect_longterm_unpinnable_folios( + struct list_head *movable_folio_list, + struct pages_or_folios *pofs) +{ + unsigned long collected = 0; + struct folio *folio; + int drained = 0; + long i = 0; + + for (folio = pofs_get_folio(pofs, i); folio; + folio = pofs_next_folio(folio, pofs, &i)) { + + if (folio_is_longterm_pinnable(folio)) + continue; + + collected++; + + if (folio_is_device_coherent(folio)) + continue; + + if (folio_test_hugetlb(folio)) { + folio_isolate_hugetlb(folio, movable_folio_list); + continue; + } + + if (drained == 0 && folio_may_be_lru_cached(folio) && + folio_ref_count(folio) != + folio_expected_ref_count(folio) + 1) { + lru_add_drain(); + drained = 1; + } + if (drained == 1 && folio_may_be_lru_cached(folio) && + folio_ref_count(folio) != + folio_expected_ref_count(folio) + 1) { + lru_add_drain_all(); + drained = 2; + } + + if (!folio_isolate_lru(folio)) + continue; + + list_add_tail(&folio->lru, movable_folio_list); + node_stat_mod_folio(folio, + NR_ISOLATED_ANON + folio_is_file_lru(folio), + folio_nr_pages(folio)); + } + + return collected; +} + +/* + * Unpins all folios and migrates device coherent folios and movable_folio_list. + * Returns -EAGAIN if all folios were successfully migrated or -errno for + * failure (or partial success). + */ +static int +migrate_longterm_unpinnable_folios(struct list_head *movable_folio_list, + struct pages_or_folios *pofs) +{ + int ret; + unsigned long i; + + for (i = 0; i < pofs->nr_entries; i++) { + struct folio *folio = pofs_get_folio(pofs, i); + + if (folio_is_device_coherent(folio)) { + /* + * Migration will fail if the folio is pinned, so + * convert the pin on the source folio to a normal + * reference. + */ + pofs_clear_entry(pofs, i); + folio_get(folio); + gup_put_folio(folio, 1, FOLL_PIN); + + if (migrate_device_coherent_folio(folio)) { + ret = -EBUSY; + goto err; + } + + continue; + } + + /* + * We can't migrate folios with unexpected references, so drop + * the reference obtained by __get_user_pages_locked(). + * Migrating folios have been added to movable_folio_list after + * calling folio_isolate_lru() which takes a reference so the + * folio won't be freed if it's migrating. + */ + unpin_folio(folio); + pofs_clear_entry(pofs, i); + } + + if (!list_empty(movable_folio_list)) { + struct migration_target_control mtc = { + .nid = NUMA_NO_NODE, + .gfp_mask = GFP_USER | __GFP_NOWARN, + .reason = MR_LONGTERM_PIN, + }; + + if (migrate_pages(movable_folio_list, alloc_migration_target, + NULL, (unsigned long)&mtc, MIGRATE_SYNC, + MR_LONGTERM_PIN, NULL)) { + ret = -ENOMEM; + goto err; + } + } + + putback_movable_pages(movable_folio_list); + + return -EAGAIN; + +err: + pofs_unpin(pofs); + putback_movable_pages(movable_folio_list); + + return ret; +} + +static long +check_and_migrate_movable_pages_or_folios(struct pages_or_folios *pofs) +{ + LIST_HEAD(movable_folio_list); + unsigned long collected; + + collected = collect_longterm_unpinnable_folios(&movable_folio_list, + pofs); + if (!collected) + return 0; + + return migrate_longterm_unpinnable_folios(&movable_folio_list, pofs); +} + +/* + * Check whether all folios are *allowed* to be pinned indefinitely (long term). + * Rather confusingly, all folios in the range are required to be pinned via + * FOLL_PIN, before calling this routine. + * + * Return values: + * + * 0: if everything is OK and all folios in the range are allowed to be pinned, + * then this routine leaves all folios pinned and returns zero for success. + * + * -EAGAIN: if any folios in the range are not allowed to be pinned, then this + * routine will migrate those folios away, unpin all the folios in the range. If + * migration of the entire set of folios succeeds, then -EAGAIN is returned. The + * caller should re-pin the entire range with FOLL_PIN and then call this + * routine again. + * + * -ENOMEM, or any other -errno: if an error *other* than -EAGAIN occurs, this + * indicates a migration failure. The caller should give up, and propagate the + * error back up the call stack. The caller does not need to unpin any folios in + * that case, because this routine will do the unpinning. + */ +static long check_and_migrate_movable_folios(unsigned long nr_folios, + struct folio **folios) +{ + struct pages_or_folios pofs = { + .folios = folios, + .has_folios = true, + .nr_entries = nr_folios, + }; + + return check_and_migrate_movable_pages_or_folios(&pofs); +} + +/* + * Return values and behavior are the same as those for + * check_and_migrate_movable_folios(). + */ +static long check_and_migrate_movable_pages(unsigned long nr_pages, + struct page **pages) +{ + struct pages_or_folios pofs = { + .pages = pages, + .has_folios = false, + .nr_entries = nr_pages, + }; + + return check_and_migrate_movable_pages_or_folios(&pofs); +} +#else +static long check_and_migrate_movable_pages(unsigned long nr_pages, + struct page **pages) +{ + return 0; +} + +static long check_and_migrate_movable_folios(unsigned long nr_folios, + struct folio **folios) +{ + return 0; +} +#endif /* CONFIG_MIGRATION */ + +/* + * __gup_longterm_locked() is a wrapper for __get_user_pages_locked which + * allows us to process the FOLL_LONGTERM flag. + */ +static long __gup_longterm_locked(struct mm_struct *mm, + unsigned long start, + unsigned long nr_pages, + struct page **pages, + int *locked, + unsigned int gup_flags) +{ + unsigned int flags; + long rc, nr_pinned_pages; + + if (!(gup_flags & FOLL_LONGTERM)) + return __get_user_pages_locked(mm, start, nr_pages, pages, + locked, gup_flags); + + flags = memalloc_pin_save(); + do { + nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages, + pages, locked, + gup_flags); + if (nr_pinned_pages <= 0) { + rc = nr_pinned_pages; + break; + } + + /* FOLL_LONGTERM implies FOLL_PIN */ + rc = check_and_migrate_movable_pages(nr_pinned_pages, pages); + } while (rc == -EAGAIN); + memalloc_pin_restore(flags); + return rc ? rc : nr_pinned_pages; +} + +/* + * Check that the given flags are valid for the exported gup/pup interface, and + * update them with the required flags that the caller must have set. + */ +static bool is_valid_gup_args(struct page **pages, int *locked, + unsigned int *gup_flags_p, unsigned int to_set) +{ + unsigned int gup_flags = *gup_flags_p; + + /* + * These flags not allowed to be specified externally to the gup + * interfaces: + * - FOLL_TOUCH/FOLL_PIN/FOLL_TRIED/FOLL_FAST_ONLY are internal only + * - FOLL_REMOTE is internal only, set in (get|pin)_user_pages_remote() + * - FOLL_UNLOCKABLE is internal only and used if locked is !NULL + */ + if (WARN_ON_ONCE(gup_flags & INTERNAL_GUP_FLAGS)) + return false; + + gup_flags |= to_set; + if (locked) { + /* At the external interface locked must be set */ + if (WARN_ON_ONCE(*locked != 1)) + return false; + + gup_flags |= FOLL_UNLOCKABLE; + } + + /* FOLL_GET and FOLL_PIN are mutually exclusive. */ + if (WARN_ON_ONCE((gup_flags & (FOLL_PIN | FOLL_GET)) == + (FOLL_PIN | FOLL_GET))) + return false; + + /* LONGTERM can only be specified when pinning */ + if (WARN_ON_ONCE(!(gup_flags & FOLL_PIN) && (gup_flags & FOLL_LONGTERM))) + return false; + + /* Pages input must be given if using GET/PIN */ + if (WARN_ON_ONCE((gup_flags & (FOLL_GET | FOLL_PIN)) && !pages)) + return false; + + /* We want to allow the pgmap to be hot-unplugged at all times */ + if (WARN_ON_ONCE((gup_flags & FOLL_LONGTERM) && + (gup_flags & FOLL_PCI_P2PDMA))) + return false; + + *gup_flags_p = gup_flags; + return true; +} + +#ifdef CONFIG_MMU +/** + * get_user_pages_remote() - pin user pages in memory + * @mm: mm_struct of target mm + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * @locked: pointer to lock flag indicating whether lock is held and + * subsequently whether VM_FAULT_RETRY functionality can be + * utilised. Lock must initially be held. + * + * Returns either number of pages pinned (which may be less than the + * number requested), or an error. Details about the return value: + * + * -- If nr_pages is 0, returns 0. + * -- If nr_pages is >0, but no pages were pinned, returns -errno. + * -- If nr_pages is >0, and some pages were pinned, returns the number of + * pages pinned. Again, this may be less than nr_pages. + * + * The caller is responsible for releasing returned @pages, via put_page(). + * + * Must be called with mmap_lock held for read or write. + * + * get_user_pages_remote walks a process's page tables and takes a reference + * to each struct page that each user address corresponds to at a given + * instant. That is, it takes the page that would be accessed if a user + * thread accesses the given user virtual address at that instant. + * + * This does not guarantee that the page exists in the user mappings when + * get_user_pages_remote returns, and there may even be a completely different + * page there in some cases (eg. if mmapped pagecache has been invalidated + * and subsequently re-faulted). However it does guarantee that the page + * won't be freed completely. And mostly callers simply care that the page + * contains data that was valid *at some point in time*. Typically, an IO + * or similar operation cannot guarantee anything stronger anyway because + * locks can't be held over the syscall boundary. + * + * If gup_flags & FOLL_WRITE == 0, the page must not be written to. If the page + * is written to, set_page_dirty (or set_page_dirty_lock, as appropriate) must + * be called after the page is finished with, and before put_page is called. + * + * get_user_pages_remote is typically used for fewer-copy IO operations, + * to get a handle on the memory by some means other than accesses + * via the user virtual addresses. The pages may be submitted for + * DMA to devices or accessed via their kernel linear mapping (via the + * kmap APIs). Care should be taken to use the correct cache flushing APIs. + * + * See also get_user_pages_fast, for performance critical applications. + * + * get_user_pages_remote should be phased out in favor of + * get_user_pages_locked|unlocked or get_user_pages_fast. Nothing + * should use get_user_pages_remote because it cannot pass + * FAULT_FLAG_ALLOW_RETRY to handle_mm_fault. + */ +long get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + int local_locked = 1; + + if (!is_valid_gup_args(pages, locked, &gup_flags, + FOLL_TOUCH | FOLL_REMOTE)) + return -EINVAL; + + return __get_user_pages_locked(mm, start, nr_pages, pages, + locked ? locked : &local_locked, + gup_flags); +} +EXPORT_SYMBOL(get_user_pages_remote); + +#else /* CONFIG_MMU */ +long get_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) +{ + return 0; +} +#endif /* !CONFIG_MMU */ + +/** + * get_user_pages() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. Or NULL, if caller + * only intends to ensure the pages are faulted in. + * + * This is the same as get_user_pages_remote(), just with a less-flexible + * calling convention where we assume that the mm being operated on belongs to + * the current task, and doesn't allow passing of a locked parameter. We also + * obviously don't pass FOLL_REMOTE in here. + */ +long get_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int locked = 1; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_TOUCH)) + return -EINVAL; + + return __get_user_pages_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(get_user_pages); + /* - * Generic Fast GUP + * get_user_pages_unlocked() is suitable to replace the form: + * + * mmap_read_lock(mm); + * get_user_pages(mm, ..., pages, NULL); + * mmap_read_unlock(mm); + * + * with: + * + * get_user_pages_unlocked(mm, ..., pages); + * + * It is functionally equivalent to get_user_pages_fast so + * get_user_pages_fast should be used instead if specific gup_flags + * (e.g. FOLL_FORCE) are not required. + */ +long get_user_pages_unlocked(unsigned long start, unsigned long nr_pages, + struct page **pages, unsigned int gup_flags) +{ + int locked = 0; + + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_TOUCH | FOLL_UNLOCKABLE)) + return -EINVAL; + + return __get_user_pages_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(get_user_pages_unlocked); + +/* + * GUP-fast * * get_user_pages_fast attempts to pin user pages by walking the page * tables directly and avoids taking locks. Thus the walker needs to be @@ -1352,104 +2698,218 @@ struct page *get_dump_page(unsigned long addr) * * Another way to achieve this is to batch up page table containing pages * belonging to more than one mm_user, then rcu_sched a callback to free those - * pages. Disabling interrupts will allow the fast_gup walker to both block + * pages. Disabling interrupts will allow the gup_fast() walker to both block * the rcu_sched callback, and an IPI that we broadcast for splitting THPs * (which is a relatively rare event). The code below adopts this strategy. * * Before activating this code, please be aware that the following assumptions * are currently made: * - * *) Either HAVE_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to + * *) Either MMU_GATHER_RCU_TABLE_FREE is enabled, and tlb_remove_table() is used to * free pages containing page tables or TLB flushing requires IPI broadcast. * * *) ptes can be read atomically by the architecture. * - * *) access_ok is sufficient to validate userspace address ranges. + * *) valid user addresses are below TASK_MAX_SIZE * * The last two assumptions can be relaxed by the addition of helper functions. * * This code is based heavily on the PowerPC implementation by Nick Piggin. */ -#ifdef CONFIG_HAVE_GENERIC_GUP - -#ifndef gup_get_pte +#ifdef CONFIG_HAVE_GUP_FAST /* - * We assume that the PTE can be read atomically. If this is not the case for - * your architecture, please provide the helper. + * Used in the GUP-fast path to determine whether GUP is permitted to work on + * a specific folio. + * + * This call assumes the caller has pinned the folio, that the lowest page table + * level still points to this folio, and that interrupts have been disabled. + * + * GUP-fast must reject all secretmem folios. + * + * Writing to pinned file-backed dirty tracked folios is inherently problematic + * (see comment describing the writable_file_mapping_allowed() function). We + * therefore try to avoid the most egregious case of a long-term mapping doing + * so. + * + * This function cannot be as thorough as that one as the VMA is not available + * in the fast path, so instead we whitelist known good cases and if in doubt, + * fall back to the slow path. */ -static inline pte_t gup_get_pte(pte_t *ptep) +static bool gup_fast_folio_allowed(struct folio *folio, unsigned int flags) { - return READ_ONCE(*ptep); + bool reject_file_backed = false; + struct address_space *mapping; + bool check_secretmem = false; + unsigned long mapping_flags; + + /* + * If we aren't pinning then no problematic write can occur. A long term + * pin is the most egregious case so this is the one we disallow. + */ + if ((flags & (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) == + (FOLL_PIN | FOLL_LONGTERM | FOLL_WRITE)) + reject_file_backed = true; + + /* We hold a folio reference, so we can safely access folio fields. */ + + /* secretmem folios are always order-0 folios. */ + if (IS_ENABLED(CONFIG_SECRETMEM) && !folio_test_large(folio)) + check_secretmem = true; + + if (!reject_file_backed && !check_secretmem) + return true; + + if (WARN_ON_ONCE(folio_test_slab(folio))) + return false; + + /* hugetlb neither requires dirty-tracking nor can be secretmem. */ + if (folio_test_hugetlb(folio)) + return true; + + /* + * GUP-fast disables IRQs. When IRQS are disabled, RCU grace periods + * cannot proceed, which means no actions performed under RCU can + * proceed either. + * + * inodes and thus their mappings are freed under RCU, which means the + * mapping cannot be freed beneath us and thus we can safely dereference + * it. + */ + lockdep_assert_irqs_disabled(); + + /* + * However, there may be operations which _alter_ the mapping, so ensure + * we read it once and only once. + */ + mapping = READ_ONCE(folio->mapping); + + /* + * The mapping may have been truncated, in any case we cannot determine + * if this mapping is safe - fall back to slow path to determine how to + * proceed. + */ + if (!mapping) + return false; + + /* Anonymous folios pose no problem. */ + mapping_flags = (unsigned long)mapping & FOLIO_MAPPING_FLAGS; + if (mapping_flags) + return mapping_flags & FOLIO_MAPPING_ANON; + + /* + * At this point, we know the mapping is non-null and points to an + * address_space object. + */ + if (check_secretmem && secretmem_mapping(mapping)) + return false; + /* The only remaining allowed file system is shmem. */ + return !reject_file_backed || shmem_mapping(mapping); } -#endif -static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages) +static void __maybe_unused gup_fast_undo_dev_pagemap(int *nr, int nr_start, + unsigned int flags, struct page **pages) { while ((*nr) - nr_start) { - struct page *page = pages[--(*nr)]; + struct folio *folio = page_folio(pages[--(*nr)]); - ClearPageReferenced(page); - put_page(page); + folio_clear_referenced(folio); + gup_put_folio(folio, 1, flags); } } #ifdef CONFIG_ARCH_HAS_PTE_SPECIAL -static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +/* + * GUP-fast relies on pte change detection to avoid concurrent pgtable + * operations. + * + * To pin the page, GUP-fast needs to do below in order: + * (1) pin the page (by prefetching pte), then (2) check pte not changed. + * + * For the rest of pgtable operations where pgtable updates can be racy + * with GUP-fast, we need to do (1) clear pte, then (2) check whether page + * is pinned. + * + * Above will work for all pte-level operations, including THP split. + * + * For THP collapse, it's a bit more complicated because GUP-fast may be + * walking a pgtable page that is being freed (pte is still valid but pmd + * can be cleared already). To avoid race in such condition, we need to + * also check pmd here to make sure pmd doesn't change (corresponds to + * pmdp_collapse_flush() in the THP collapse code path). + */ +static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { - struct dev_pagemap *pgmap = NULL; - int nr_start = *nr, ret = 0; + int ret = 0; pte_t *ptep, *ptem; ptem = ptep = pte_offset_map(&pmd, addr); + if (!ptep) + return 0; do { - pte_t pte = gup_get_pte(ptep); - struct page *head, *page; + pte_t pte = ptep_get_lockless(ptep); + struct page *page; + struct folio *folio; /* - * Similar to the PMD case below, NUMA hinting must take slow - * path using the pte_protnone check. + * Always fallback to ordinary GUP on PROT_NONE-mapped pages: + * pte_access_permitted() better should reject these pages + * either way: otherwise, GUP-fast might succeed in + * cases where ordinary GUP would fail due to VMA access + * permissions. */ if (pte_protnone(pte)) goto pte_unmap; - if (!pte_access_permitted(pte, write)) + if (!pte_access_permitted(pte, flags & FOLL_WRITE)) goto pte_unmap; - if (pte_devmap(pte)) { - pgmap = get_dev_pagemap(pte_pfn(pte), pgmap); - if (unlikely(!pgmap)) { - undo_dev_pagemap(nr, nr_start, pages); - goto pte_unmap; - } - } else if (pte_special(pte)) + if (pte_special(pte)) goto pte_unmap; - VM_BUG_ON(!pfn_valid(pte_pfn(pte))); + /* If it's not marked as special it must have a valid memmap. */ + VM_WARN_ON_ONCE(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - head = compound_head(page); - if (!page_cache_get_speculative(head)) + folio = try_grab_folio_fast(page, 1, flags); + if (!folio) goto pte_unmap; - if (unlikely(pte_val(pte) != pte_val(*ptep))) { - put_page(head); + if (unlikely(pmd_val(pmd) != pmd_val(*pmdp)) || + unlikely(pte_val(pte) != pte_val(ptep_get(ptep)))) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } + + if (!gup_fast_folio_allowed(folio, flags)) { + gup_put_folio(folio, 1, flags); goto pte_unmap; } - VM_BUG_ON_PAGE(compound_head(page) != head, page); + if (!pte_write(pte) && gup_must_unshare(NULL, flags, page)) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } - SetPageReferenced(page); + /* + * We need to make the page accessible if and only if we are + * going to access its content (the FOLL_PIN case). Please + * see Documentation/core-api/pin_user_pages.rst for + * details. + */ + if ((flags & FOLL_PIN) && arch_make_folio_accessible(folio)) { + gup_put_folio(folio, 1, flags); + goto pte_unmap; + } + folio_set_referenced(folio); pages[*nr] = page; (*nr)++; - } while (ptep++, addr += PAGE_SIZE, addr != end); ret = 1; pte_unmap: - if (pgmap) - put_dev_pagemap(pgmap); pte_unmap(ptem); return ret; } @@ -1461,440 +2921,648 @@ pte_unmap: * to be special. * * For a futex to be placed on a THP tail page, get_futex_key requires a - * __get_user_pages_fast implementation that can pin pages. Thus it's still - * useful to have gup_huge_pmd even if we can't operate on ptes. + * get_user_pages_fast_only implementation that can pin pages. Thus it's still + * useful to have gup_fast_pmd_leaf even if we can't operate on ptes. */ -static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { return 0; } #endif /* CONFIG_ARCH_HAS_PTE_SPECIAL */ -#if defined(__HAVE_ARCH_PTE_DEVMAP) && defined(CONFIG_TRANSPARENT_HUGEPAGE) -static int __gup_device_huge(unsigned long pfn, unsigned long addr, - unsigned long end, struct page **pages, int *nr) -{ - int nr_start = *nr; - struct dev_pagemap *pgmap = NULL; - - do { - struct page *page = pfn_to_page(pfn); - - pgmap = get_dev_pagemap(pfn, pgmap); - if (unlikely(!pgmap)) { - undo_dev_pagemap(nr, nr_start, pages); - return 0; - } - SetPageReferenced(page); - pages[*nr] = page; - get_page(page); - (*nr)++; - pfn++; - } while (addr += PAGE_SIZE, addr != end); - - if (pgmap) - put_dev_pagemap(pgmap); - return 1; -} - -static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, - unsigned long end, struct page **pages, int *nr) +static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { - unsigned long fault_pfn; - int nr_start = *nr; + struct page *page; + struct folio *folio; + int refs; - fault_pfn = pmd_pfn(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); - if (!__gup_device_huge(fault_pfn, addr, end, pages, nr)) + if (!pmd_access_permitted(orig, flags & FOLL_WRITE)) return 0; - if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { - undo_dev_pagemap(nr, nr_start, pages); + if (pmd_special(orig)) return 0; - } - return 1; -} -static int __gup_device_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, - unsigned long end, struct page **pages, int *nr) -{ - unsigned long fault_pfn; - int nr_start = *nr; + refs = (end - addr) >> PAGE_SHIFT; + page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); - fault_pfn = pud_pfn(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); - if (!__gup_device_huge(fault_pfn, addr, end, pages, nr)) + folio = try_grab_folio_fast(page, refs, flags); + if (!folio) return 0; - if (unlikely(pud_val(orig) != pud_val(*pudp))) { - undo_dev_pagemap(nr, nr_start, pages); + if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { + gup_put_folio(folio, refs, flags); return 0; } - return 1; -} -#else -static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, - unsigned long end, struct page **pages, int *nr) -{ - BUILD_BUG(); - return 0; -} - -static int __gup_device_huge_pud(pud_t pud, pud_t *pudp, unsigned long addr, - unsigned long end, struct page **pages, int *nr) -{ - BUILD_BUG(); - return 0; -} -#endif -static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr, - unsigned long end, int write, struct page **pages, int *nr) -{ - struct page *head, *page; - int refs; - - if (!pmd_access_permitted(orig, write)) - return 0; - - if (pmd_devmap(orig)) - return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr); - - refs = 0; - page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); - - head = compound_head(pmd_page(orig)); - if (!page_cache_add_speculative(head, refs)) { - *nr -= refs; + if (!gup_fast_folio_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); return 0; } - - if (unlikely(pmd_val(orig) != pmd_val(*pmdp))) { - *nr -= refs; - while (refs--) - put_page(head); + if (!pmd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); return 0; } - SetPageReferenced(head); + pages += *nr; + *nr += refs; + for (; refs; refs--) + *(pages++) = page++; + folio_set_referenced(folio); return 1; } -static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr, - unsigned long end, int write, struct page **pages, int *nr) +static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { - struct page *head, *page; + struct page *page; + struct folio *folio; int refs; - if (!pud_access_permitted(orig, write)) + if (!pud_access_permitted(orig, flags & FOLL_WRITE)) return 0; - if (pud_devmap(orig)) - return __gup_device_huge_pud(orig, pudp, addr, end, pages, nr); + if (pud_special(orig)) + return 0; - refs = 0; + refs = (end - addr) >> PAGE_SHIFT; page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); - head = compound_head(pud_page(orig)); - if (!page_cache_add_speculative(head, refs)) { - *nr -= refs; + folio = try_grab_folio_fast(page, refs, flags); + if (!folio) return 0; - } if (unlikely(pud_val(orig) != pud_val(*pudp))) { - *nr -= refs; - while (refs--) - put_page(head); + gup_put_folio(folio, refs, flags); return 0; } - SetPageReferenced(head); - return 1; -} - -static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr, - unsigned long end, int write, - struct page **pages, int *nr) -{ - int refs; - struct page *head, *page; - - if (!pgd_access_permitted(orig, write)) - return 0; - - BUILD_BUG_ON(pgd_devmap(orig)); - refs = 0; - page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT); - do { - pages[*nr] = page; - (*nr)++; - page++; - refs++; - } while (addr += PAGE_SIZE, addr != end); - - head = compound_head(pgd_page(orig)); - if (!page_cache_add_speculative(head, refs)) { - *nr -= refs; + if (!gup_fast_folio_allowed(folio, flags)) { + gup_put_folio(folio, refs, flags); return 0; } - if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) { - *nr -= refs; - while (refs--) - put_page(head); + if (!pud_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) { + gup_put_folio(folio, refs, flags); return 0; } - SetPageReferenced(head); + pages += *nr; + *nr += refs; + for (; refs; refs--) + *(pages++) = page++; + folio_set_referenced(folio); return 1; } -static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { unsigned long next; pmd_t *pmdp; - pmdp = pmd_offset(&pud, addr); + pmdp = pmd_offset_lockless(pudp, pud, addr); do { - pmd_t pmd = READ_ONCE(*pmdp); + pmd_t pmd = pmdp_get_lockless(pmdp); next = pmd_addr_end(addr, end); if (!pmd_present(pmd)) return 0; - if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd))) { - /* - * NUMA hinting faults need to be handled in the GUP - * slowpath for accounting purposes and so that they - * can be serialised against THP migration. - */ + if (unlikely(pmd_leaf(pmd))) { + /* See gup_fast_pte_range() */ if (pmd_protnone(pmd)) return 0; - if (!gup_huge_pmd(pmd, pmdp, addr, next, write, + if (!gup_fast_pmd_leaf(pmd, pmdp, addr, next, flags, pages, nr)) return 0; - } else if (unlikely(is_hugepd(__hugepd(pmd_val(pmd))))) { - /* - * architecture have different format for hugetlbfs - * pmd format and THP pmd format - */ - if (!gup_huge_pd(__hugepd(pmd_val(pmd)), addr, - PMD_SHIFT, next, write, pages, nr)) - return 0; - } else if (!gup_pte_range(pmd, addr, next, write, pages, nr)) + } else if (!gup_fast_pte_range(pmd, pmdp, addr, next, flags, + pages, nr)) return 0; } while (pmdp++, addr = next, addr != end); return 1; } -static int gup_pud_range(p4d_t p4d, unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +static int gup_fast_pud_range(p4d_t *p4dp, p4d_t p4d, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { unsigned long next; pud_t *pudp; - pudp = pud_offset(&p4d, addr); + pudp = pud_offset_lockless(p4dp, p4d, addr); do { - pud_t pud = READ_ONCE(*pudp); + pud_t pud = pudp_get(pudp); next = pud_addr_end(addr, end); - if (pud_none(pud)) + if (unlikely(!pud_present(pud))) return 0; - if (unlikely(pud_huge(pud))) { - if (!gup_huge_pud(pud, pudp, addr, next, write, - pages, nr)) - return 0; - } else if (unlikely(is_hugepd(__hugepd(pud_val(pud))))) { - if (!gup_huge_pd(__hugepd(pud_val(pud)), addr, - PUD_SHIFT, next, write, pages, nr)) + if (unlikely(pud_leaf(pud))) { + if (!gup_fast_pud_leaf(pud, pudp, addr, next, flags, + pages, nr)) return 0; - } else if (!gup_pmd_range(pud, addr, next, write, pages, nr)) + } else if (!gup_fast_pmd_range(pudp, pud, addr, next, flags, + pages, nr)) return 0; } while (pudp++, addr = next, addr != end); return 1; } -static int gup_p4d_range(pgd_t pgd, unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +static int gup_fast_p4d_range(pgd_t *pgdp, pgd_t pgd, unsigned long addr, + unsigned long end, unsigned int flags, struct page **pages, + int *nr) { unsigned long next; p4d_t *p4dp; - p4dp = p4d_offset(&pgd, addr); + p4dp = p4d_offset_lockless(pgdp, pgd, addr); do { - p4d_t p4d = READ_ONCE(*p4dp); + p4d_t p4d = p4dp_get(p4dp); next = p4d_addr_end(addr, end); - if (p4d_none(p4d)) + if (!p4d_present(p4d)) return 0; - BUILD_BUG_ON(p4d_huge(p4d)); - if (unlikely(is_hugepd(__hugepd(p4d_val(p4d))))) { - if (!gup_huge_pd(__hugepd(p4d_val(p4d)), addr, - P4D_SHIFT, next, write, pages, nr)) - return 0; - } else if (!gup_pud_range(p4d, addr, next, write, pages, nr)) + BUILD_BUG_ON(p4d_leaf(p4d)); + if (!gup_fast_pud_range(p4dp, p4d, addr, next, flags, + pages, nr)) return 0; } while (p4dp++, addr = next, addr != end); return 1; } -static void gup_pgd_range(unsigned long addr, unsigned long end, - int write, struct page **pages, int *nr) +static void gup_fast_pgd_range(unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) { unsigned long next; pgd_t *pgdp; pgdp = pgd_offset(current->mm, addr); do { - pgd_t pgd = READ_ONCE(*pgdp); + pgd_t pgd = pgdp_get(pgdp); next = pgd_addr_end(addr, end); if (pgd_none(pgd)) return; - if (unlikely(pgd_huge(pgd))) { - if (!gup_huge_pgd(pgd, pgdp, addr, next, write, - pages, nr)) - return; - } else if (unlikely(is_hugepd(__hugepd(pgd_val(pgd))))) { - if (!gup_huge_pd(__hugepd(pgd_val(pgd)), addr, - PGDIR_SHIFT, next, write, pages, nr)) - return; - } else if (!gup_p4d_range(pgd, addr, next, write, pages, nr)) + BUILD_BUG_ON(pgd_leaf(pgd)); + if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags, + pages, nr)) return; } while (pgdp++, addr = next, addr != end); } +#else +static inline void gup_fast_pgd_range(unsigned long addr, unsigned long end, + unsigned int flags, struct page **pages, int *nr) +{ +} +#endif /* CONFIG_HAVE_GUP_FAST */ #ifndef gup_fast_permitted /* - * Check if it's allowed to use __get_user_pages_fast() for the range, or + * Check if it's allowed to use get_user_pages_fast_only() for the range, or * we need to fall back to the slow version: */ -bool gup_fast_permitted(unsigned long start, int nr_pages, int write) +static bool gup_fast_permitted(unsigned long start, unsigned long end) { - unsigned long len, end; - - len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; - return end >= start; + return true; } #endif -/* - * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to - * the regular GUP. - * Note a difference with get_user_pages_fast: this always returns the - * number of pages pinned, 0 if no pages were pinned. - */ -int __get_user_pages_fast(unsigned long start, int nr_pages, int write, - struct page **pages) +static unsigned long gup_fast(unsigned long start, unsigned long end, + unsigned int gup_flags, struct page **pages) { - unsigned long len, end; unsigned long flags; - int nr = 0; - - start &= PAGE_MASK; - len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; + int nr_pinned = 0; + unsigned seq; - if (unlikely(!access_ok((void __user *)start, len))) + if (!IS_ENABLED(CONFIG_HAVE_GUP_FAST) || + !gup_fast_permitted(start, end)) return 0; + if (gup_flags & FOLL_PIN) { + if (!raw_seqcount_try_begin(¤t->mm->write_protect_seq, seq)) + return 0; + } + /* - * Disable interrupts. We use the nested form as we can already have - * interrupts disabled by get_futex_key. + * Disable interrupts. The nested form is used, in order to allow full, + * general purpose use of this routine. * - * With interrupts disabled, we block page table pages from being - * freed from under us. See struct mmu_table_batch comments in + * With interrupts disabled, we block page table pages from being freed + * from under us. See struct mmu_table_batch comments in * include/asm-generic/tlb.h for more details. * - * We do not adopt an rcu_read_lock(.) here as we also want to - * block IPIs that come from THPs splitting. + * We do not adopt an rcu_read_lock() here as we also want to block IPIs + * that come from callers of tlb_remove_table_sync_one(). */ + local_irq_save(flags); + gup_fast_pgd_range(start, end, gup_flags, pages, &nr_pinned); + local_irq_restore(flags); - if (gup_fast_permitted(start, nr_pages, write)) { - local_irq_save(flags); - gup_pgd_range(start, end, write, pages, &nr); - local_irq_restore(flags); + /* + * When pinning pages for DMA there could be a concurrent write protect + * from fork() via copy_page_range(), in this case always fail GUP-fast. + */ + if (gup_flags & FOLL_PIN) { + if (read_seqcount_retry(¤t->mm->write_protect_seq, seq)) { + gup_fast_unpin_user_pages(pages, nr_pinned); + return 0; + } else { + sanity_check_pinned_pages(pages, nr_pinned); + } } + return nr_pinned; +} + +static int gup_fast_fallback(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages) +{ + unsigned long len, end; + unsigned long nr_pinned; + int locked = 0; + int ret; + + if (WARN_ON_ONCE(gup_flags & ~(FOLL_WRITE | FOLL_LONGTERM | + FOLL_FORCE | FOLL_PIN | FOLL_GET | + FOLL_FAST_ONLY | FOLL_NOFAULT | + FOLL_PCI_P2PDMA | FOLL_HONOR_NUMA_FAULT))) + return -EINVAL; + + if (gup_flags & FOLL_PIN) + mm_set_has_pinned_flag(current->mm); + + if (!(gup_flags & FOLL_FAST_ONLY)) + might_lock_read(¤t->mm->mmap_lock); - return nr; + start = untagged_addr(start) & PAGE_MASK; + len = nr_pages << PAGE_SHIFT; + if (check_add_overflow(start, len, &end)) + return -EOVERFLOW; + if (end > TASK_SIZE_MAX) + return -EFAULT; + + nr_pinned = gup_fast(start, end, gup_flags, pages); + if (nr_pinned == nr_pages || gup_flags & FOLL_FAST_ONLY) + return nr_pinned; + + /* Slow path: try to get the remaining pages with get_user_pages */ + start += nr_pinned << PAGE_SHIFT; + pages += nr_pinned; + ret = __gup_longterm_locked(current->mm, start, nr_pages - nr_pinned, + pages, &locked, + gup_flags | FOLL_TOUCH | FOLL_UNLOCKABLE); + if (ret < 0) { + /* + * The caller has to unpin the pages we already pinned so + * returning -errno is not an option + */ + if (nr_pinned) + return nr_pinned; + return ret; + } + return ret + nr_pinned; +} + +/** + * get_user_pages_fast_only() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Like get_user_pages_fast() except it's IRQ-safe in that it won't fall back to + * the regular GUP. + * + * If the architecture does not support this function, simply return with no + * pages pinned. + * + * Careful, careful! COW breaking can go either way, so a non-write + * access can get ambiguous page results. If you call this function without + * 'write' set, you'd better be sure that you're ok with that ambiguity. + */ +int get_user_pages_fast_only(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * Internally (within mm/gup.c), gup fast variants must set FOLL_GET, + * because gup fast is always a "pin with a +1 page refcount" request. + * + * FOLL_FAST_ONLY is required in order to match the API description of + * this routine: no fall back to regular ("slow") GUP. + */ + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_GET | FOLL_FAST_ONLY)) + return -EINVAL; + + return gup_fast_fallback(start, nr_pages, gup_flags, pages); } +EXPORT_SYMBOL_GPL(get_user_pages_fast_only); /** * get_user_pages_fast() - pin user pages in memory + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Attempt to pin user pages in memory without taking mm->mmap_lock. + * If not successful, it will fall back to taking the lock and + * calling get_user_pages(). + * + * Returns number of pages pinned. This may be fewer than the number requested. + * If nr_pages is 0 or negative, returns 0. If no pages were pinned, returns + * -errno. + */ +int get_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + /* + * The caller may or may not have explicitly set FOLL_GET; either way is + * OK. However, internally (within mm/gup.c), gup fast variants must set + * FOLL_GET, because gup fast is always a "pin with a +1 page refcount" + * request. + */ + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_GET)) + return -EINVAL; + return gup_fast_fallback(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(get_user_pages_fast); + +/** + * pin_user_pages_fast() - pin user pages in memory without taking locks + * + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying pin behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Nearly the same as get_user_pages_fast(), except that FOLL_PIN is set. See + * get_user_pages_fast() for documentation on the function arguments, because + * the arguments here are identical. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for further details. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page() will not remove pins from it. + */ +int pin_user_pages_fast(unsigned long start, int nr_pages, + unsigned int gup_flags, struct page **pages) +{ + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN)) + return -EINVAL; + return gup_fast_fallback(start, nr_pages, gup_flags, pages); +} +EXPORT_SYMBOL_GPL(pin_user_pages_fast); + +/** + * pin_user_pages_remote() - pin pages of a remote process + * + * @mm: mm_struct of target mm * @start: starting user address * @nr_pages: number of pages from start to pin - * @write: whether pages will be written to + * @gup_flags: flags modifying lookup behaviour * @pages: array that receives pointers to the pages pinned. * Should be at least nr_pages long. + * @locked: pointer to lock flag indicating whether lock is held and + * subsequently whether VM_FAULT_RETRY functionality can be + * utilised. Lock must initially be held. * - * Attempt to pin user pages in memory without taking mm->mmap_sem. - * If not successful, it will fall back to taking the lock and - * calling get_user_pages(). + * Nearly the same as get_user_pages_remote(), except that FOLL_PIN is set. See + * get_user_pages_remote() for documentation on the function arguments, because + * the arguments here are identical. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for details. * - * Returns number of pages pinned. This may be fewer than the number - * requested. If nr_pages is 0 or negative, returns 0. If no pages - * were pinned, returns -errno. + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. */ -int get_user_pages_fast(unsigned long start, int nr_pages, int write, - struct page **pages) +long pin_user_pages_remote(struct mm_struct *mm, + unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages, + int *locked) { - unsigned long addr, len, end; - int nr = 0, ret = 0; + int local_locked = 1; - start &= PAGE_MASK; - addr = start; - len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; + if (!is_valid_gup_args(pages, locked, &gup_flags, + FOLL_PIN | FOLL_TOUCH | FOLL_REMOTE)) + return 0; + return __gup_longterm_locked(mm, start, nr_pages, pages, + locked ? locked : &local_locked, + gup_flags); +} +EXPORT_SYMBOL(pin_user_pages_remote); + +/** + * pin_user_pages() - pin user pages in memory for use by other devices + * + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @gup_flags: flags modifying lookup behaviour + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Nearly the same as get_user_pages(), except that FOLL_TOUCH is not set, and + * FOLL_PIN is set. + * + * FOLL_PIN means that the pages must be released via unpin_user_page(). Please + * see Documentation/core-api/pin_user_pages.rst for details. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. + */ +long pin_user_pages(unsigned long start, unsigned long nr_pages, + unsigned int gup_flags, struct page **pages) +{ + int locked = 1; - if (nr_pages <= 0) + if (!is_valid_gup_args(pages, NULL, &gup_flags, FOLL_PIN)) return 0; + return __gup_longterm_locked(current->mm, start, nr_pages, + pages, &locked, gup_flags); +} +EXPORT_SYMBOL(pin_user_pages); - if (unlikely(!access_ok((void __user *)start, len))) - return -EFAULT; +/* + * pin_user_pages_unlocked() is the FOLL_PIN variant of + * get_user_pages_unlocked(). Behavior is the same, except that this one sets + * FOLL_PIN and rejects FOLL_GET. + * + * Note that if a zero_page is amongst the returned pages, it will not have + * pins in it and unpin_user_page*() will not remove pins from it. + */ +long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages, + struct page **pages, unsigned int gup_flags) +{ + int locked = 0; - if (gup_fast_permitted(start, nr_pages, write)) { - local_irq_disable(); - gup_pgd_range(addr, end, write, pages, &nr); - local_irq_enable(); - ret = nr; + if (!is_valid_gup_args(pages, NULL, &gup_flags, + FOLL_PIN | FOLL_TOUCH | FOLL_UNLOCKABLE)) + return 0; + + return __gup_longterm_locked(current->mm, start, nr_pages, pages, + &locked, gup_flags); +} +EXPORT_SYMBOL(pin_user_pages_unlocked); + +/** + * memfd_pin_folios() - pin folios associated with a memfd + * @memfd: the memfd whose folios are to be pinned + * @start: the first memfd offset + * @end: the last memfd offset (inclusive) + * @folios: array that receives pointers to the folios pinned + * @max_folios: maximum number of entries in @folios + * @offset: the offset into the first folio + * + * Attempt to pin folios associated with a memfd in the contiguous range + * [start, end]. Given that a memfd is either backed by shmem or hugetlb, + * the folios can either be found in the page cache or need to be allocated + * if necessary. Once the folios are located, they are all pinned via + * FOLL_PIN and @offset is populatedwith the offset into the first folio. + * And, eventually, these pinned folios must be released either using + * unpin_folios() or unpin_folio(). + * + * It must be noted that the folios may be pinned for an indefinite amount + * of time. And, in most cases, the duration of time they may stay pinned + * would be controlled by the userspace. This behavior is effectively the + * same as using FOLL_LONGTERM with other GUP APIs. + * + * Returns number of folios pinned, which could be less than @max_folios + * as it depends on the folio sizes that cover the range [start, end]. + * If no folios were pinned, it returns -errno. + */ +long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end, + struct folio **folios, unsigned int max_folios, + pgoff_t *offset) +{ + unsigned int flags, nr_folios, nr_found; + unsigned int i, pgshift = PAGE_SHIFT; + pgoff_t start_idx, end_idx; + struct folio *folio = NULL; + struct folio_batch fbatch; + struct hstate *h; + long ret = -EINVAL; + + if (start < 0 || start > end || !max_folios) + return -EINVAL; + + if (!memfd) + return -EINVAL; + + if (!shmem_file(memfd) && !is_file_hugepages(memfd)) + return -EINVAL; + + if (end >= i_size_read(file_inode(memfd))) + return -EINVAL; + + if (is_file_hugepages(memfd)) { + h = hstate_file(memfd); + pgshift = huge_page_shift(h); } - if (nr < nr_pages) { - /* Try to get the remaining pages with get_user_pages */ - start += nr << PAGE_SHIFT; - pages += nr; + flags = memalloc_pin_save(); + do { + nr_folios = 0; + start_idx = start >> pgshift; + end_idx = end >> pgshift; + if (is_file_hugepages(memfd)) { + start_idx <<= huge_page_order(h); + end_idx <<= huge_page_order(h); + } - ret = get_user_pages_unlocked(start, nr_pages - nr, pages, - write ? FOLL_WRITE : 0); + folio_batch_init(&fbatch); + while (start_idx <= end_idx && nr_folios < max_folios) { + /* + * In most cases, we should be able to find the folios + * in the page cache. If we cannot find them for some + * reason, we try to allocate them and add them to the + * page cache. + */ + nr_found = filemap_get_folios_contig(memfd->f_mapping, + &start_idx, + end_idx, + &fbatch); + if (folio) { + folio_put(folio); + folio = NULL; + } + + for (i = 0; i < nr_found; i++) { + folio = fbatch.folios[i]; + + if (try_grab_folio(folio, 1, FOLL_PIN)) { + folio_batch_release(&fbatch); + ret = -EINVAL; + goto err; + } + + if (nr_folios == 0) + *offset = offset_in_folio(folio, start); - /* Have to be a bit careful with return values */ - if (nr > 0) { - if (ret < 0) - ret = nr; - else - ret += nr; + folios[nr_folios] = folio; + if (++nr_folios == max_folios) + break; + } + + folio = NULL; + folio_batch_release(&fbatch); + if (!nr_found) { + folio = memfd_alloc_folio(memfd, start_idx); + if (IS_ERR(folio)) { + ret = PTR_ERR(folio); + if (ret != -EEXIST) + goto err; + folio = NULL; + } + } } - } + + ret = check_and_migrate_movable_folios(nr_folios, folios); + } while (ret == -EAGAIN); + + memalloc_pin_restore(flags); + return ret ? ret : nr_folios; +err: + memalloc_pin_restore(flags); + unpin_folios(folios, nr_folios); return ret; } +EXPORT_SYMBOL_GPL(memfd_pin_folios); -#endif /* CONFIG_HAVE_GENERIC_GUP */ +/** + * folio_add_pins() - add pins to an already-pinned folio + * @folio: the folio to add more pins to + * @pins: number of pins to add + * + * Try to add more pins to an already-pinned folio. The semantics + * of the pin (e.g., FOLL_WRITE) follow any existing pin and cannot + * be changed. + * + * This function is helpful when having obtained a pin on a large folio + * using memfd_pin_folios(), but wanting to logically unpin parts + * (e.g., individual pages) of the folio later, for example, using + * unpin_user_page_range_dirty_lock(). + * + * This is not the right interface to initially pin a folio. + */ +int folio_add_pins(struct folio *folio, unsigned int pins) +{ + VM_WARN_ON_ONCE(!folio_maybe_dma_pinned(folio)); + + return try_grab_folio(folio, pins, FOLL_PIN); +} +EXPORT_SYMBOL_GPL(folio_add_pins); |