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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 12:21:36 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-02 12:21:36 -0700
commit94709049fb8442fb2f7b91fbec3c2897a75e18df (patch)
treef1d38ea6bc9db6d5a15ba4821c83abeb7ce7fd35 /mm/gup.c
parent17839856fd588f4ab6b789f482ed3ffd7c403e1f (diff)
parent4fba37586e4e73f9f9a855e610e151ef7da2b481 (diff)
Merge branch 'akpm' (patches from Andrew)
Merge updates from Andrew Morton: "A few little subsystems and a start of a lot of MM patches. Subsystems affected by this patch series: squashfs, ocfs2, parisc, vfs. With mm subsystems: slab-generic, slub, debug, pagecache, gup, swap, memcg, pagemap, memory-failure, vmalloc, kasan" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (128 commits) kasan: move kasan_report() into report.c mm/mm_init.c: report kasan-tag information stored in page->flags ubsan: entirely disable alignment checks under UBSAN_TRAP kasan: fix clang compilation warning due to stack protector x86/mm: remove vmalloc faulting mm: remove vmalloc_sync_(un)mappings() x86/mm/32: implement arch_sync_kernel_mappings() x86/mm/64: implement arch_sync_kernel_mappings() mm/ioremap: track which page-table levels were modified mm/vmalloc: track which page-table levels were modified mm: add functions to track page directory modifications s390: use __vmalloc_node in stack_alloc powerpc: use __vmalloc_node in alloc_vm_stack arm64: use __vmalloc_node in arch_alloc_vmap_stack mm: remove vmalloc_user_node_flags mm: switch the test_vmalloc module to use __vmalloc_node mm: remove __vmalloc_node_flags_caller mm: remove both instances of __vmalloc_node_flags mm: remove the prot argument to __vmalloc_node mm: remove the pgprot argument to __vmalloc ...
Diffstat (limited to 'mm/gup.c')
-rw-r--r--mm/gup.c77
1 files changed, 58 insertions, 19 deletions
diff --git a/mm/gup.c b/mm/gup.c
index 4aa2f5ab6e1f..3edf740a3897 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1183,7 +1183,7 @@ 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.
@@ -1191,7 +1191,8 @@ static bool vma_permits_fault(struct vm_area_struct *vma,
* @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
+ * 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()
@@ -1854,7 +1855,7 @@ static long __get_user_pages_remote(struct task_struct *tsk,
gup_flags | FOLL_TOUCH | FOLL_REMOTE);
}
-/*
+/**
* 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.
@@ -1885,13 +1886,13 @@ static long __get_user_pages_remote(struct task_struct *tsk,
*
* 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
+ * 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 returns, and there may even be a completely different
+ * 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
@@ -1903,17 +1904,17 @@ static long __get_user_pages_remote(struct task_struct *tsk,
* 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.
+ * 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 should be phased out in favor of
+ * 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 because it cannot pass
+ * should use get_user_pages_remote 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,
@@ -1952,7 +1953,17 @@ static long __get_user_pages_remote(struct task_struct *tsk,
}
#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.
+ * @vmas: array of pointers to vmas corresponding to each page.
+ * Or NULL if the caller does not require them.
+ *
* 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
@@ -1975,11 +1986,7 @@ long get_user_pages(unsigned long start, unsigned long nr_pages,
}
EXPORT_SYMBOL(get_user_pages);
-/*
- * 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);
@@ -1995,6 +2002,21 @@ EXPORT_SYMBOL(get_user_pages);
* get_user_pages_locked(tsk, mm, ..., pages, &locked);
* if (locked)
* up_read(&mm->mmap_sem);
+ *
+ * @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.
+ *
+ * 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().
+ *
*/
long get_user_pages_locked(unsigned long start, unsigned long nr_pages,
unsigned int gup_flags, struct page **pages,
@@ -2971,3 +2993,20 @@ long pin_user_pages(unsigned long start, unsigned long nr_pages,
pages, vmas, gup_flags);
}
EXPORT_SYMBOL(pin_user_pages);
+
+/*
+ * 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.
+ */
+long pin_user_pages_unlocked(unsigned long start, unsigned long nr_pages,
+ struct page **pages, unsigned int gup_flags)
+{
+ /* FOLL_GET and FOLL_PIN are mutually exclusive. */
+ if (WARN_ON_ONCE(gup_flags & FOLL_GET))
+ return -EINVAL;
+
+ gup_flags |= FOLL_PIN;
+ return get_user_pages_unlocked(start, nr_pages, pages, gup_flags);
+}
+EXPORT_SYMBOL(pin_user_pages_unlocked);