The patch titled
Subject: memcg: fix deadlock by avoiding stat lock when anon
has been added to the -mm tree. Its filename is
memcg-use-new-logic-for-page-stat-accounting-fix-2.patch
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: memcg: fix deadlock by avoiding stat lock when anon
Fix deadlock in "memcg: use new logic for page stat accounting".
page_remove_rmap() first calls mem_cgroup_begin_update_page_stat(), which
may take move_lock_mem_cgroup(), unlocked at the end of page_remove_rmap()
by mem_cgroup_end_update_page_stat().
The PageAnon case never needs to mem_cgroup_dec_page_stat(page,
MEMCG_NR_FILE_MAPPED); but it often needs to mem_cgroup_uncharge_page(),
which does lock_page_cgroup(), while holding that move_lock_mem_cgroup().
Whereas mem_cgroup_move_account() calls move_lock_mem_cgroup() while
holding lock_page_cgroup().
Since mem_cgroup_begin and end are unnecessary here for PageAnon, simply
avoid the deadlock and wasted calls in that case.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Greg Thelen <gthelen@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Ying Han <yinghan@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff -puN mm/rmap.c~memcg-use-new-logic-for-page-stat-accounting-fix-2 mm/rmap.c
--- a/mm/rmap.c~memcg-use-new-logic-for-page-stat-accounting-fix-2
+++ a/mm/rmap.c
@@ -1166,10 +1166,18 @@ void page_add_file_rmap(struct page *pag
*/
void page_remove_rmap(struct page *page)
{
+ bool anon = PageAnon(page);
bool locked;
unsigned long flags;
- mem_cgroup_begin_update_page_stat(page, &locked, &flags);
+ /*
+ * The anon case has no mem_cgroup page_stat to update; but may
+ * uncharge_page() below, where the lock ordering can deadlock if
+ * we hold the lock against page_stat move: so avoid it on anon.
+ */
+ if (!anon)
+ mem_cgroup_begin_update_page_stat(page, &locked, &flags);
+
/* page still mapped by someone else? */
if (!atomic_add_negative(-1, &page->_mapcount))
goto out;
@@ -1181,7 +1189,7 @@ void page_remove_rmap(struct page *page)
* not if it's in swapcache - there might be another pte slot
* containing the swap entry, but page not yet written to swap.
*/
- if ((!PageAnon(page) || PageSwapCache(page)) &&
+ if ((!anon || PageSwapCache(page)) &&
page_test_and_clear_dirty(page_to_pfn(page), 1))
set_page_dirty(page);
/*
@@ -1190,7 +1198,7 @@ void page_remove_rmap(struct page *page)
*/
if (unlikely(PageHuge(page)))
goto out;
- if (PageAnon(page)) {
+ if (anon) {
mem_cgroup_uncharge_page(page);
if (!PageTransHuge(page))
__dec_zone_page_state(page, NR_ANON_PAGES);
@@ -1211,7 +1219,8 @@ void page_remove_rmap(struct page *page)
* faster for those pages still in swapcache.
*/
out:
- mem_cgroup_end_update_page_stat(page, &locked, &flags);
+ if (!anon)
+ mem_cgroup_end_update_page_stat(page, &locked, &flags);
}
/*
_
Subject: Subject: memcg: fix deadlock by avoiding stat lock when anon
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
linux-next.patch
memcg-fix-deadlock-by-inverting-lrucare-nesting.patch
memcg-fix-gpf-when-cgroup-removal-races-with-last-exit.patch
mm-add-rss-counters-consistency-check.patch
mm-vmscan-fix-misused-nr_reclaimed-in-shrink_mem_cgroup_zone.patch
make-swapin-readahead-skip-over-holes.patch
make-swapin-readahead-skip-over-holes-fix.patch
compact_pgdat-workaround-lockdep-warning-in-kswapd.patch
mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem-fix.patch
mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem-fix-fix.patch
mm-hugetlb-defer-freeing-pages-when-gathering-surplus-pages.patch
rmap-anon_vma_prepare-reduce-code-duplication-by-calling-anon_vma_chain_link.patch
mm-vmscan-handle-isolated-pages-with-lru-lock-released.patch
mm-hugetlb-bail-out-unmapping-after-serving-reference-page.patch
mm-hugetlb-cleanup-duplicated-code-in-unmapping-vm-range.patch
tmpfs-security-xattr-setting-on-inode-creation.patch
mm-fix-move-migrate_pages-race-on-task-struct.patch
ksm-clean-up-page_trans_compound_anon_split.patch
ksm-cleanup-introduce-ksm_check_mm.patch
ksm-cleanup-introduce-ksm_check_mm-fix.patch
hugetlbfs-drop-taking-inode-i_mutex-lock-from-hugetlbfs_read.patch
memcg-replace-mem_cont-by-mem_res_ctlr.patch
memcg-replace-mem-and-mem_cont-stragglers.patch
memcg-lru_size-instead-of-mem_cgroup_zstat.patch
memcg-enum-lru_list-lru.patch
memcg-remove-redundant-returns.patch
idr-make-idr_get_next-good-for-rcu_read_lock.patch
cgroup-revert-ss_id_lock-to-spinlock.patch
memcg-let-css_get_next-rely-upon-rcu_read_lock.patch
memcg-remove-pcg_cache-page_cgroup-flag.patch
memcg-remove-pcg_cache-page_cgroup-flag-checkpatch-fixes.patch
memcg-remove-pcg_cache-page_cgroup-flag-fix.patch
memcg-use-new-logic-for-page-stat-accounting-fix-2.patch
memcg-remove-pcg_file_mapped-fix-cosmetic-fix.patch
memcg-remove-pcg_file_mapped-fix-42.patch
prio_tree-debugging-patch.patch
--
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