Subject: + mm-munlock-fix-deadlock-in-__munlock_pagevec.patch added to -mm tree
To:
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
From: [email protected]
Date: Mon, 16 Dec 2013 16:34:37 -0800
The patch titled
Subject: mm: munlock: fix deadlock in __munlock_pagevec()
has been added to the -mm tree. Its filename is
mm-munlock-fix-deadlock-in-__munlock_pagevec.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-munlock-fix-deadlock-in-__munlock_pagevec.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-munlock-fix-deadlock-in-__munlock_pagevec.patch
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------------------------------------------------------
From: Vlastimil Babka <[email protected]>
Subject: mm: munlock: fix deadlock in __munlock_pagevec()
Commit 7225522bb ("mm: munlock: batch non-THP page isolation and
munlock+putback using pagevec" introduced __munlock_pagevec() to speed up
munlock by holding lru_lock over multiple isolated pages. Pages that fail
to be isolated are put_page()d immediately, also within the lock.
This can lead to deadlock when __munlock_pagevec() becomes the holder of
the last page pin and put_page() leads to __page_cache_release() which
also locks lru_lock. The deadlock has been observed by Sasha Levin using
trinity.
This patch avoids the deadlock by deferring put_page() operations until
lru_lock is released. Another pagevec (which is also used by later phases
of the function is reused to gather the pages for put_page() operation.
Signed-off-by: Vlastimil Babka <[email protected]>
Reported-by: Sasha Levin <[email protected]>
Cc: Michel Lespinasse <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
mm/mlock.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff -puN mm/mlock.c~mm-munlock-fix-deadlock-in-__munlock_pagevec mm/mlock.c
--- a/mm/mlock.c~mm-munlock-fix-deadlock-in-__munlock_pagevec
+++ a/mm/mlock.c
@@ -295,10 +295,12 @@ static void __munlock_pagevec(struct pag
{
int i;
int nr = pagevec_count(pvec);
- int delta_munlocked = -nr;
+ int delta_munlocked;
struct pagevec pvec_putback;
int pgrescued = 0;
+ pagevec_init(&pvec_putback, 0);
+
/* Phase 1: page isolation */
spin_lock_irq(&zone->lru_lock);
for (i = 0; i < nr; i++) {
@@ -327,16 +329,22 @@ skip_munlock:
/*
* We won't be munlocking this page in the next phase
* but we still need to release the follow_page_mask()
- * pin.
+ * pin. We cannot do it under lru_lock however. If it's
+ * the last pin, __page_cache_release would deadlock.
*/
+ pagevec_add(&pvec_putback, pvec->pages[i]);
pvec->pages[i] = NULL;
- put_page(page);
- delta_munlocked++;
}
}
+ delta_munlocked = -nr + pagevec_count(&pvec_putback);
__mod_zone_page_state(zone, NR_MLOCK, delta_munlocked);
spin_unlock_irq(&zone->lru_lock);
+ /* Now we can release pins of pages that we are not munlocking */
+ for (i = 0; i < pagevec_count(&pvec_putback); i++) {
+ put_page(pvec_putback.pages[i]);
+ }
+
/* Phase 2: page munlock */
pagevec_init(&pvec_putback, 0);
for (i = 0; i < nr; i++) {
_
Patches currently in -mm which might be from [email protected] are
mm-mempolicy-correct-putback-method-for-isolate-pages-if-failed.patch
mm-compaction-respect-ignore_skip_hint-in-update_pageblock_skip.patch
mm-mmapc-add-mlock_future_check-helper.patch
mm-mlock-prepare-params-outside-critical-region.patch
mm-compaction-trace-compaction-begin-and-end.patch
mm-compaction-encapsulate-defer-reset-logic.patch
mm-compaction-reset-cached-scanner-pfns-before-reading-them.patch
mm-compaction-detect-when-scanners-meet-in-isolate_freepages.patch
mm-compaction-do-not-mark-unmovable-pageblocks-as-skipped-in-async-compaction.patch
mm-compaction-reset-scanner-positions-immediately-when-they-meet.patch
mm-migrate-add-comment-about-permanent-failure-path.patch
mm-migrate-correct-failure-handling-if-hugepage_migration_support.patch
mm-migrate-remove-putback_lru_pages-fix-comment-on-putback_movable_pages.patch
mm-migrate-remove-unused-function-fail_migrate_page.patch
mm-documentation-remove-hopelessly-out-of-date-locking-doc.patch
mm-munlock-fix-a-bug-where-thp-tail-page-is-encountered.patch
mm-munlock-fix-deadlock-in-__munlock_pagevec.patch
mm-munlock-fix-deadlock-in-__munlock_pagevec-fix.patch
mm-munlock-fix-potential-race-with-thp-page-split.patch
mm-munlock-fix-potential-race-with-thp-page-split-fix.patch
linux-next.patch
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