Subject: + mm-try_to_unmap_cluster-should-lock_page-before-mlocking.patch added
to -mm tree
To:
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
From: [email protected]
Date: Thu, 20 Mar 2014 15:53:48 -0700
The patch titled
Subject: mm: try_to_unmap_cluster() should lock_page() before mlocking
has been added to the -mm tree. Its filename is
mm-try_to_unmap_cluster-should-lock_page-before-mlocking.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-try_to_unmap_cluster-should-lock_page-before-mlocking.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-try_to_unmap_cluster-should-lock_page-before-mlocking.patch
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------------------------------------------------------
From: Vlastimil Babka <[email protected]>
Subject: mm: try_to_unmap_cluster() should lock_page() before mlocking
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 <[email protected]>
Signed-off-by: Bob Liu <[email protected]>
Reported-by: Sasha Levin <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
mm/mlock.c | 2 ++
mm/rmap.c | 14 ++++++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff -puN mm/mlock.c~mm-try_to_unmap_cluster-should-lock_page-before-mlocking
mm/mlock.c
--- a/mm/mlock.c~mm-try_to_unmap_cluster-should-lock_page-before-mlocking
+++ a/mm/mlock.c
@@ -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)) {
@@ -174,6 +175,7 @@ unsigned int munlock_vma_page(struct pag
unsigned int nr_pages;
struct zone *zone = page_zone(page);
+ /* For try_to_munlock() and to serialize with page migration */
BUG_ON(!PageLocked(page));
/*
diff -puN mm/rmap.c~mm-try_to_unmap_cluster-should-lock_page-before-mlocking
mm/rmap.c
--- a/mm/rmap.c~mm-try_to_unmap_cluster-should-lock_page-before-mlocking
+++ a/mm/rmap.c
@@ -1318,9 +1318,19 @@ static int try_to_unmap_cluster(unsigned
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 */
}
_
Patches currently in -mm which might be from [email protected] are
mm-vmstat-fix-up-zone-state-accounting.patch
fs-cachefiles-use-add_to_page_cache_lru.patch
lib-radix-tree-radix_tree_delete_item.patch
mm-shmem-save-one-radix-tree-lookup-when-truncating-swapped-pages.patch
mm-filemap-move-radix-tree-hole-searching-here.patch
mm-fs-prepare-for-non-page-entries-in-page-cache-radix-trees.patch
mm-fs-store-shadow-entries-in-page-cache.patch
mm-thrash-detection-based-file-cache-sizing.patch
lib-radix_tree-tree-node-interface.patch
mm-keep-page-cache-radix-tree-nodes-in-check.patch
mm-compaction-disallow-high-order-page-for-migration-target.patch
mm-compaction-do-not-call-suitable_migration_target-on-every-page.patch
mm-compaction-change-the-timing-to-check-to-drop-the-spinlock.patch
mm-compaction-check-pageblock-suitability-once-per-pageblock.patch
mm-compaction-clean-up-code-on-success-of-ballon-isolation.patch
mm-compactionc-isolate_freepages_block-small-tuneup.patch
mm-compaction-determine-isolation-mode-only-once.patch
mm-try_to_unmap_cluster-should-lock_page-before-mlocking.patch
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