vmpressure: make sure there are no events queued after memcg is offlined (33cb876e) · Commits · 戴 / test

vmpressure is called synchronously from reclaim where the target_memcg is guaranteed to be alive but the eventfd is signaled from the work queue context. This means that memcg (along with vmpressure structure which is embedded into it) might go away while the work item is pending which would result in use-after-release bug. We have two possible ways how to fix this. Either vmpressure pins memcg before it schedules vmpr->work and unpin it in vmpressure_work_fn or explicitely flush the work item from the css_offline context (as suggested by Tejun). This patch implements the later one and it introduces vmpressure_cleanup which flushes the vmpressure work queue item item. It hooks into mem_cgroup_css_offline after the memcg itself is cleaned up. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by:

Michal Hocko <mhocko@suse.cz> Reported-by:

Tejun Heo <tj@kernel.org> Cc: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Li Zefan <lizefan@huawei.com> Acked-by:

Tejun Heo <tj@kernel.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/vmpressure.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -30,6 +30,7 @@ extern void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
		extern void vmpressure_prio(gfp_t gfp, struct mem_cgroup *memcg, int prio);

		extern void vmpressure_init(struct vmpressure *vmpr);
		extern void vmpressure_cleanup(struct vmpressure *vmpr);
		extern struct vmpressure memcg_to_vmpressure(struct mem_cgroup memcg);
		extern struct cgroup_subsys_state vmpressure_to_css(struct vmpressure vmpr);
		extern struct vmpressure css_to_vmpressure(struct cgroup_subsys_state css);

mm/memcontrol.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -6335,6 +6335,7 @@ static void mem_cgroup_css_offline(struct cgroup *cont)
		mem_cgroup_invalidate_reclaim_iterators(memcg);
		mem_cgroup_reparent_charges(memcg);
		mem_cgroup_destroy_all_caches(memcg);
		vmpressure_cleanup(&memcg->vmpressure);
		}

		static void mem_cgroup_css_free(struct cgroup *cont)

mm/vmpressure.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -372,3 +372,19 @@ void vmpressure_init(struct vmpressure *vmpr)
		INIT_LIST_HEAD(&vmpr->events);
		INIT_WORK(&vmpr->work, vmpressure_work_fn);
		}

		/**
		* vmpressure_cleanup() - shuts down vmpressure control structure
		* @vmpr: Structure to be cleaned up
		*
		* This function should be called before the structure in which it is
		* embedded is cleaned up.
		*/
		void vmpressure_cleanup(struct vmpressure *vmpr)
		{
		/*
		* Make sure there is no pending work before eventfd infrastructure
		* goes away.
		*/
		flush_work(&vmpr->work);
		}

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