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| author |   Mel Gorman <mel@csn.ul.ie> | 2009-12-14 17:59:53 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2009-12-15 08:53:23 -0800 |
| commit | 4eb2b1dcd598f8489130405c81c60c289896d92a (patch) | |
| tree | 87bf0dec35f55688595447de65eb95952eb3dabc /mm | |
| parent | 'sysctl_max_map_count' should be non-negative (diff) | |
| download | linux-dev-4eb2b1dcd598f8489130405c81c60c289896d92a.tar.xz linux-dev-4eb2b1dcd598f8489130405c81c60c289896d92a.zip | |
hugetlb: acquire the i_mmap_lock before walking the prio_tree to unmap a page
When the owner of a mapping fails COW because a child process is holding a
reference, the children VMAs are walked and the page is unmapped. The
i_mmap_lock is taken for the unmapping of the page but not the walking of
the prio_tree. In theory, that tree could be changing if the lock is not
held. This patch takes the i_mmap_lock properly for the duration of the
prio_tree walk.
[hugh.dickins@tiscali.co.uk: Spotted the problem in the first place]
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Acked-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/hugetlb.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 2ef66a2a148d..6df8065039eb 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2237,6 +2237,12 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma, + (vma->vm_pgoff >> PAGE_SHIFT); mapping = (struct address_space *)page_private(page); + /* + * Take the mapping lock for the duration of the table walk. As + * this mapping should be shared between all the VMAs, + * __unmap_hugepage_range() is called as the lock is already held + */ + spin_lock(&mapping->i_mmap_lock); vma_prio_tree_foreach(iter_vma, &iter, &mapping->i_mmap, pgoff, pgoff) { /* Do not unmap the current VMA */ if (iter_vma == vma) @@ -2250,10 +2256,11 @@ static int unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma, * from the time of fork. This would look like data corruption */ if (!is_vma_resv_set(iter_vma, HPAGE_RESV_OWNER)) - unmap_hugepage_range(iter_vma, + __unmap_hugepage_range(iter_vma, address, address + huge_page_size(h), page); } + spin_unlock(&mapping->i_mmap_lock); return 1; } |