The patch titled
Subject: mm: memcontrol: fix missed end-writeback page accounting fix
has been added to the -mm tree. Its filename is
mm-memcontrol-fix-missed-end-writeback-page-accounting-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-memcontrol-fix-missed-end-writeback-page-accounting-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-memcontrol-fix-missed-end-writeback-page-accounting-fix.patch
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------------------------------------------------------
From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: memcontrol: fix missed end-writeback page accounting fix
Add kernel-doc to page state accounting functions.
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 51 +++++++++++++++++++++++++++++++---------------
1 file changed, 35 insertions(+), 16 deletions(-)
diff -puN mm/memcontrol.c~mm-memcontrol-fix-missed-end-writeback-page-accounting-fix mm/memcontrol.c
--- a/mm/memcontrol.c~mm-memcontrol-fix-missed-end-writeback-page-accounting-fix
+++ a/mm/memcontrol.c
@@ -2198,21 +2198,31 @@ cleanup:
return true;
}
-/*
- * Used to update mapped file or writeback or other statistics.
+/**
+ * mem_cgroup_begin_page_stat - begin a page state statistics transaction
+ * @page: page that is going to change accounted state
+ * @locked: &memcg->move_lock slowpath was taken
+ * @flags: IRQ-state flags for &memcg->move_lock
*
- * Notes: Race condition
+ * This function must mark the beginning of an accounted page state
+ * change to prevent double accounting when the page is concurrently
+ * being moved to another memcg:
*
- * Charging occurs during page instantiation, while the page is
- * unmapped and locked in page migration, or while the page table is
- * locked in THP migration. No race is possible.
+ * memcg = mem_cgroup_begin_page_stat(page, &locked, &flags);
+ * if (TestClearPageState(page))
+ * mem_cgroup_update_page_stat(memcg, state, -1);
+ * mem_cgroup_end_page_stat(memcg, locked, flags);
*
- * Uncharge happens to pages with zero references, no race possible.
+ * The RCU lock is held throughout the transaction. The fast path can
+ * get away without acquiring the memcg->move_lock (@locked is false)
+ * because page moving starts with an RCU grace period.
*
- * Charge moving between groups is protected by checking mm->moving
- * account and taking the move_lock in the slowpath.
+ * The RCU lock also protects the memcg from being freed when the page
+ * state that is going to change is the only thing preventing the page
+ * from being uncharged. E.g. end-writeback clearing PageWriteback(),
+ * which allows migration to go ahead and uncharge the page before the
+ * account transaction might be complete.
*/
-
struct mem_cgroup *mem_cgroup_begin_page_stat(struct page *page,
bool *locked,
unsigned long *flags)
@@ -2230,12 +2240,7 @@ again:
memcg = pc->mem_cgroup;
if (unlikely(!memcg || !PageCgroupUsed(pc)))
return NULL;
- /*
- * If this memory cgroup is not under account moving, we don't
- * need to take move_lock_mem_cgroup(). Because we already hold
- * rcu_read_lock(), any calls to move_account will be delayed until
- * rcu_read_unlock().
- */
+
*locked = false;
if (atomic_read(&memcg->moving_account) <= 0)
return memcg;
@@ -2250,6 +2255,12 @@ again:
return memcg;
}
+/**
+ * mem_cgroup_end_page_stat - finish a page state statistics transaction
+ * @memcg: the memcg that was accounted against
+ * @locked: value received from mem_cgroup_begin_page_stat()
+ * @flags: value received from mem_cgroup_begin_page_stat()
+ */
void mem_cgroup_end_page_stat(struct mem_cgroup *memcg, bool locked,
unsigned long flags)
{
@@ -2259,6 +2270,14 @@ void mem_cgroup_end_page_stat(struct mem
rcu_read_unlock();
}
+/**
+ * mem_cgroup_update_page_stat - update page state statistics
+ * @memcg: memcg to account against
+ * @idx: page state item to account
+ * @val: number of pages (positive or negative)
+ *
+ * See mem_cgroup_begin_page_stat() for locking requirements.
+ */
void mem_cgroup_update_page_stat(struct mem_cgroup *memcg,
enum mem_cgroup_stat_index idx, int val)
{
_
Patches currently in -mm which might be from hannes@xxxxxxxxxxx are
cgroup-kmemleak-add-kmemleak_free-for-cgroup-deallocations.patch
mm-page-writeback-inline-account_page_dirtied-into-single-caller.patch
mm-memcontrol-fix-missed-end-writeback-page-accounting.patch
mm-memcontrol-fix-missed-end-writeback-page-accounting-fix.patch
mm-memcontrol-lockless-page-counters.patch
mm-memcontrol-lockless-page-counters-fix.patch
mm-memcontrol-lockless-page-counters-fix-fix.patch
mm-memcontrol-lockless-page-counters-fix-2.patch
mm-hugetlb_cgroup-convert-to-lockless-page-counters.patch
kernel-res_counter-remove-the-unused-api.patch
kernel-res_counter-remove-the-unused-api-fix.patch
kernel-res_counter-remove-the-unused-api-fix-2.patch
mm-memcontrol-convert-reclaim-iterator-to-simple-css-refcounting.patch
mm-memcontrol-convert-reclaim-iterator-to-simple-css-refcounting-fix.patch
mm-memcontrol-take-a-css-reference-for-each-charged-page.patch
mm-memcontrol-remove-obsolete-kmemcg-pinning-tricks.patch
mm-memcontrol-continue-cache-reclaim-from-offlined-groups.patch
mm-memcontrol-remove-synchroneous-stock-draining-code.patch
mm-vmscan-count-only-dirty-pages-as-congested.patch
memcg-simplify-unreclaimable-groups-handling-in-soft-limit-reclaim.patch
mm-memcontrol-update-mem_cgroup_page_lruvec-documentation.patch
mm-memcontrol-clarify-migration-where-old-page-is-uncharged.patch
memcg-remove-activate_kmem_mutex.patch
mm-memcontrol-micro-optimize-mem_cgroup_split_huge_fixup.patch
mm-memcontrol-uncharge-pages-on-swapout.patch
mm-memcontrol-uncharge-pages-on-swapout-fix.patch
mm-memcontrol-remove-unnecessary-pcg_memsw-memoryswap-charge-flag.patch
mm-memcontrol-remove-unnecessary-pcg_mem-memory-charge-flag.patch
mm-memcontrol-remove-unnecessary-pcg_used-pc-mem_cgroup-valid-flag.patch
mm-memcontrol-remove-unnecessary-pcg_used-pc-mem_cgroup-valid-flag-fix.patch
mm-memcontrol-inline-memcg-move_lock-locking.patch
mm-memcontrol-dont-pass-a-null-memcg-to-mem_cgroup_end_move.patch
mm-memcontrol-fold-mem_cgroup_start_move-mem_cgroup_end_move.patch
debugging-keep-track-of-page-owners.patch
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