Subject: + mm-munlock-fix-deadlock-in-__munlock_pagevec.patch added to -mm tree To: vbabka@xxxxxxx,aarcange@xxxxxxxxxx,hughd@xxxxxxxxxx,mgorman@xxxxxxx,riel@xxxxxxxxxx,sasha.levin@xxxxxxxxxx,stable@xxxxxxxxxxxxxxx,walken@xxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx 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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Vlastimil Babka <vbabka@xxxxxxx> 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 <vbabka@xxxxxxx> Reported-by: Sasha Levin <sasha.levin@xxxxxxxxxx> Cc: Michel Lespinasse <walken@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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 vbabka@xxxxxxx 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html