mm: fix kernel BUG at mm/rmap.c:1017!

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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 5f70b962cc "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>

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This commit is contained in:

Hugh Dickins 2011-05-28 13:17:04 -07:00 • committed by Linus Torvalds

parent 826267cf1e

commit 5dbe0af47f

1 changed files with 2 additions and 2 deletions

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mm/rmap.c

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