@@ -79,6 +79,7 @@ void clear_page_mlock(struct page *page)
*/
void mlock_vma_page(struct page *page)
{
+ /* Serialize with page migration */
BUG_ON(!PageLocked(page));
if (!TestSetPageMlocked(page)) {
@@ -153,6 +154,7 @@ unsigned int munlock_vma_page(struct page *page)
{
unsigned int nr_pages;
+ /* For try_to_munlock() and to serialize with page migration */
BUG_ON(!PageLocked(page));
if (TestClearPageMlocked(page)) {
@@ -1389,9 +1389,19 @@ 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 */
}
This is a note to let you know that I have just added a patch titled mm: try_to_unmap_cluster() should lock_page() before mlocking to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11.1. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 94a3e116d5bc4944b458c98061cd0cb788c2c8a1 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka <vbabka@suse.cz> Date: Mon, 7 Apr 2014 15:37:50 -0700 Subject: 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> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- mm/mlock.c | 2 ++ mm/rmap.c | 14 ++++++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) -- 1.9.1