Commit f6f989c5 authored by Chris Down's avatar Chris Down Committed by Linus Torvalds
Browse files

mm, memcg: prevent memory.high load/store tearing 



A mem_cgroup's high attribute can be concurrently set at the same time as
we are trying to read it -- for example, if we are in memory_high_write at
the same time as we are trying to do high reclaim.

Signed-off-by: default avatarChris Down <chris@chrisdown.name>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarMichal 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/2f66f7038ed1d4688e59de72b627ae0ea52efa83.1584034301.git.chris@chrisdown.name


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c1514c0a

mm/memcontrol.c

+7 −6
Original line number Diff line number Diff line
@@ -2242,7 +2242,7 @@ static void reclaim_high(struct mem_cgroup *memcg, 
			 gfp_t gfp_mask)

{

	do {

		if (page_counter_read(&memcg->memory) <= memcg->high)

		if (page_counter_read(&memcg->memory) <= READ_ONCE(memcg->high))

			continue;

		memcg_memory_event(memcg, MEMCG_HIGH);

		try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
@@ -2582,7 +2582,7 @@ done_restock: 
	 * reclaim, the cost of mismatch is negligible.

	 */

	do {

		if (page_counter_read(&memcg->memory) > memcg->high) {

		if (page_counter_read(&memcg->memory) > READ_ONCE(memcg->high)) {

			/* Don't bother a random interrupted task */

			if (in_interrupt()) {

				schedule_work(&memcg->high_work);
@@ -4325,7 +4325,8 @@ void mem_cgroup_wb_stats(struct bdi_writeback *wb, unsigned long *pfilepages, 
	*pheadroom = PAGE_COUNTER_MAX;



	while ((parent = parent_mem_cgroup(memcg))) {

		unsigned long ceiling = min(memcg->memory.max, memcg->high);

		unsigned long ceiling = min(memcg->memory.max,

					    READ_ONCE(memcg->high));

		unsigned long used = page_counter_read(&memcg->memory);



		*pheadroom = min(*pheadroom, ceiling - min(ceiling, used));
@@ -5047,7 +5048,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) 
	if (!memcg)

		return ERR_PTR(error);



	memcg->high = PAGE_COUNTER_MAX;

	WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);

	memcg->soft_limit = PAGE_COUNTER_MAX;

	if (parent) {

		memcg->swappiness = mem_cgroup_swappiness(parent);
@@ -5200,7 +5201,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css) 
	page_counter_set_max(&memcg->tcpmem, PAGE_COUNTER_MAX);

	page_counter_set_min(&memcg->memory, 0);

	page_counter_set_low(&memcg->memory, 0);

	memcg->high = PAGE_COUNTER_MAX;

	WRITE_ONCE(memcg->high, PAGE_COUNTER_MAX);

	memcg->soft_limit = PAGE_COUNTER_MAX;

	memcg_wb_domain_size_changed(memcg);

}
@@ -6016,7 +6017,7 @@ static ssize_t memory_high_write(struct kernfs_open_file *of, 
	if (err)

		return err;



	memcg->high = high;

	WRITE_ONCE(memcg->high, high);



	for (;;) {

		unsigned long nr_pages = page_counter_read(&memcg->memory);

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