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authorChris Down <chris@chrisdown.name>2020-04-01 21:07:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-04-02 09:35:29 -0700
commitc3d532008661da197997fc6d8098190eef9344ad (patch)
treec8ce41c0a1244c279675a4ac01c7f06eb190ee49 /mm/page_counter.c
parentf86b810c2610b08afc82218068d1dfeef02dd0a1 (diff)
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mm, memcg: prevent memory.min 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/e809b4e6b0c1626dac6945970de06409a180ee65.1584034301.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.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/page_counter.c b/mm/page_counter.c
index 509143f232d8..c56db2d5e159 100644
--- a/mm/page_counter.c
+++ b/mm/page_counter.c
@@ -17,14 +17,15 @@ static void propagate_protected_usage(struct page_counter *c,
unsigned long usage)
{
unsigned long protected, old_protected;
- unsigned long low;
+ unsigned long low, min;
long delta;
if (!c->parent)
return;
- if (c->min || atomic_long_read(&c->min_usage)) {
- protected = min(usage, c->min);
+ min = READ_ONCE(c->min);
+ if (min || atomic_long_read(&c->min_usage)) {
+ protected = min(usage, min);
old_protected = atomic_long_xchg(&c->min_usage, protected);
delta = protected - old_protected;
if (delta)
@@ -207,7 +208,7 @@ void page_counter_set_min(struct page_counter *counter, unsigned long nr_pages)
{
struct page_counter *c;
- counter->min = nr_pages;
+ WRITE_ONCE(counter->min, nr_pages);
for (c = counter; c; c = c->parent)
propagate_protected_usage(c, atomic_long_read(&c->usage));