diff options
| author | Chris Down <chris@chrisdown.name> | 2020-04-01 21:07:24 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-04-02 09:35:28 -0700 |
| commit | f86b810c2610b08afc82218068d1dfeef02dd0a1 (patch) | |
| tree | 75c734e95fcf41e1cd7f53801b1631c90a5158b4 /mm/page_counter.c | |
| parent | 15b42562d46debadaebd77ac1a647abae139a231 (diff) | |
mm, memcg: prevent memory.low load/store tearing
This can be set concurrently with reads, which may cause the wrong value
to be propagated.
Signed-off-by: Chris Down <chris@chrisdown.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/448206f44b0fa7be9dad2ca2601d2bcb2c0b7844.1584034301.git.chris@chrisdown.name
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_counter.c')
| -rw-r--r-- | mm/page_counter.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/mm/page_counter.c b/mm/page_counter.c index 75d53f15f040..509143f232d8 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -17,6 +17,7 @@ static void propagate_protected_usage(struct page_counter *c, unsigned long usage) { unsigned long protected, old_protected; + unsigned long low; long delta; if (!c->parent) @@ -30,8 +31,9 @@ static void propagate_protected_usage(struct page_counter *c, atomic_long_add(delta, &c->parent->children_min_usage); } - if (c->low || atomic_long_read(&c->low_usage)) { - protected = min(usage, c->low); + low = READ_ONCE(c->low); + if (low || atomic_long_read(&c->low_usage)) { + protected = min(usage, low); old_protected = atomic_long_xchg(&c->low_usage, protected); delta = protected - old_protected; if (delta) @@ -222,7 +224,7 @@ void page_counter_set_low(struct page_counter *counter, unsigned long nr_pages) { struct page_counter *c; - counter->low = nr_pages; + WRITE_ONCE(counter->low, nr_pages); for (c = counter; c; c = c->parent) propagate_protected_usage(c, atomic_long_read(&c->usage)); |