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| author | Hugh Dickins <hughd@google.com> | 2011-05-28 13:17:04 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2011-05-28 16:09:26 -0700 |
| commit | 5dbe0af47f8a8f968bac2991c3ec974c6e3eaabc (patch) | |
| tree | e936955d61fc2a69e36b2e9276f5ad7585134255 /mm/rmap.c | |
| parent | 826267cf1e6c6899eda1325a19f1b1d15c558b20 (diff) | |
| download | lwn-5dbe0af47f8a8f968bac2991c3ec974c6e3eaabc.tar.gz lwn-5dbe0af47f8a8f968bac2991c3ec974c6e3eaabc.zip | |
mm: fix kernel BUG at mm/rmap.c:1017!
I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap()
just once. The stack showed khugepaged allocation trying to compact
pages: the call to page_add_anon_rmap() coming from remove_migration_pte().
That path holds anon_vma lock, but does not hold mmap_sem: it can
therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap:
avoid unnecessary anon_vma lock" we just took away the anon_vma lock
protection when adjusting vma->vm_end.
I don't think that particular BUG_ON ever caught anything interesting,
so better replace it by a comment, than reinstate the anon_vma locking.
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 3a39b518a653..ba58ca36fc90 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1014,7 +1014,7 @@ void do_page_add_anon_rmap(struct page *page, return; VM_BUG_ON(!PageLocked(page)); - VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* address might be in next vma when migration races vma_adjust */ if (first) __page_set_anon_rmap(page, vma, address, exclusive); else @@ -1709,7 +1709,7 @@ void hugepage_add_anon_rmap(struct page *page, BUG_ON(!PageLocked(page)); BUG_ON(!anon_vma); - BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* address might be in next vma when migration races vma_adjust */ first = atomic_inc_and_test(&page->_mapcount); if (first) __hugepage_set_anon_rmap(page, vma, address, 0); |