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authorHugh Dickins <hughd@google.com>2011-05-28 13:17:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-05-28 16:09:26 -0700
commit5dbe0af47f8a8f968bac2991c3ec974c6e3eaabc (patch)
treee936955d61fc2a69e36b2e9276f5ad7585134255 /mm/rmap.c
parent826267cf1e6c6899eda1325a19f1b1d15c558b20 (diff)
downloadlwn-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.c4
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);