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| author | Vlastimil Babka <vbabka@suse.cz> | 2014-04-07 15:37:50 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-08-07 12:00:11 -0700 |
| commit | 21dbd45fb3355f60ac73371e4612a3aa26d07124 (patch) | |
| tree | 37d11f86d1a4c00dd0d85cddc917a8c1316dfd19 /mm/rmap.c | |
| parent | 9c98268072b611fab39eee633e3f2e7b2d8c64da (diff) | |
| download | linux-stable-21dbd45fb3355f60ac73371e4612a3aa26d07124.tar.gz linux-stable-21dbd45fb3355f60ac73371e4612a3aa26d07124.tar.bz2 linux-stable-21dbd45fb3355f60ac73371e4612a3aa26d07124.zip | |
mm: try_to_unmap_cluster() should lock_page() before mlocking
commit 57e68e9cd65b4b8eb4045a1e0d0746458502554c upstream.
A BUG_ON(!PageLocked) was triggered in mlock_vma_page() by Sasha Levin
fuzzing with trinity. The call site try_to_unmap_cluster() does not lock
the pages other than its check_page parameter (which is already locked).
The BUG_ON in mlock_vma_page() is not documented and its purpose is
somewhat unclear, but apparently it serializes against page migration,
which could otherwise fail to transfer the PG_mlocked flag. This would
not be fatal, as the page would be eventually encountered again, but
NR_MLOCK accounting would become distorted nevertheless. This patch adds
a comment to the BUG_ON in mlock_vma_page() and munlock_vma_page() to that
effect.
The call site try_to_unmap_cluster() is fixed so that for page !=
check_page, trylock_page() is attempted (to avoid possible deadlocks as we
already have check_page locked) and mlock_vma_page() is performed only
upon success. If the page lock cannot be obtained, the page is left
without PG_mlocked, which is again not a problem in the whole unevictable
memory design.
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Bob Liu <bob.liu@oracle.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm/rmap.c')
| -rw-r--r-- | mm/rmap.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c index 6dc46f345dba..695eaff55d77 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1449,9 +1449,19 @@ static int try_to_unmap_cluster(unsigned long cursor, unsigned int *mapcount, BUG_ON(!page || PageAnon(page)); if (locked_vma) { - mlock_vma_page(page); /* no-op if already mlocked */ - if (page == check_page) + if (page == check_page) { + /* we know we have check_page locked */ + mlock_vma_page(page); ret = SWAP_MLOCK; + } else if (trylock_page(page)) { + /* + * If we can lock the page, perform mlock. + * Otherwise leave the page alone, it will be + * eventually encountered again later. + */ + mlock_vma_page(page); + unlock_page(page); + } continue; /* don't unmap */ } |