mm, memcg: prevent memory.low load/store tearing (f86b810c) · Commits · 戴 / test

This can be set concurrently with reads, which may cause the wrong value to be propagated. Signed-off-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:

mm/page_counter.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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));