diff options
| author | Hugh Dickins <hughd@google.com> | 2022-03-02 17:35:30 -0800 |
|---|---|---|
| committer | Matthew Wilcox (Oracle) <willy@infradead.org> | 2022-03-03 12:47:07 -0500 |
| commit | c8263bd605009355edf781f2dd711de633998475 (patch) | |
| tree | 1f42b6f88f6932e834bbbcfd4832be674506b3ef | |
| parent | 47d4f3eeef5f7fd346640fa8b49a942b506d2659 (diff) | |
mm/munlock: mlock_vma_page() check against VM_SPECIAL
Although mmap_region() and mlock_fixup() take care that VM_LOCKED
is never left set on a VM_SPECIAL vma, there is an interval while
file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may
still be set while VM_SPECIAL bits are added: so mlock_vma_page()
should ignore VM_LOCKED while any VM_SPECIAL bits are set.
This showed up as a "Bad page" still mlocked, when vfree()ing pages
which had been vm_inserted by remap_vmalloc_range_partial(): while
release_pages() and __page_cache_release(), and so put_page(), catch
pages still mlocked when freeing (and clear_page_mlock() caught them
when unmapping), the vfree() path is unprepared for them: fix it?
but these pages should not have been mlocked in the first place.
I assume that an mlockall(MCL_FUTURE) had been done in the past; or
maybe the user got to specify MAP_LOCKED on a vmalloc'ing driver mmap.
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
| -rw-r--r-- | mm/internal.h | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/internal.h b/mm/internal.h index 18af980bb1b8..450a2c8a43f3 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -413,8 +413,15 @@ void mlock_page(struct page *page); static inline void mlock_vma_page(struct page *page, struct vm_area_struct *vma, bool compound) { - /* VM_IO check prevents migration from double-counting during mlock */ - if (unlikely((vma->vm_flags & (VM_LOCKED|VM_IO)) == VM_LOCKED) && + /* + * The VM_SPECIAL check here serves two purposes. + * 1) VM_IO check prevents migration from double-counting during mlock. + * 2) Although mmap_region() and mlock_fixup() take care that VM_LOCKED + * is never left set on a VM_SPECIAL vma, there is an interval while + * file->f_op->mmap() is using vm_insert_page(s), when VM_LOCKED may + * still be set while VM_SPECIAL bits are added: so ignore it then. + */ + if (unlikely((vma->vm_flags & (VM_LOCKED|VM_SPECIAL)) == VM_LOCKED) && (compound || !PageTransCompound(page))) mlock_page(page); } |