Commit 6da66806 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-cgroup: fix list corruption from resetting io stat 



Since commit 3b8cc629 ("blk-cgroup: Optimize blkcg_rstat_flush()"),
each iostat instance is added to blkcg percpu list, so blkcg_reset_stats()
can't reset the stat instance by memset(), otherwise the llist may be
corrupted.

Fix the issue by only resetting the counter part.

Cc: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Jay Shin <jaeshin@redhat.com>
Fixes: 3b8cc629 ("blk-cgroup: Optimize blkcg_rstat_flush()")
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarWaiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240515013157.443672-2-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent efb905ae

block/blk-cgroup.c

+35 −23
Original line number Diff line number Diff line
@@ -618,12 +618,45 @@ static void blkg_destroy_all(struct gendisk *disk) 
	spin_unlock_irq(&q->queue_lock);

}



static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)

{

	int i;



	for (i = 0; i < BLKG_IOSTAT_NR; i++) {

		dst->bytes[i] = src->bytes[i];

		dst->ios[i] = src->ios[i];

	}

}



static void __blkg_clear_stat(struct blkg_iostat_set *bis)

{

	struct blkg_iostat cur = {0};

	unsigned long flags;



	flags = u64_stats_update_begin_irqsave(&bis->sync);

	blkg_iostat_set(&bis->cur, &cur);

	blkg_iostat_set(&bis->last, &cur);

	u64_stats_update_end_irqrestore(&bis->sync, flags);

}



static void blkg_clear_stat(struct blkcg_gq *blkg)

{

	int cpu;



	for_each_possible_cpu(cpu) {

		struct blkg_iostat_set *s = per_cpu_ptr(blkg->iostat_cpu, cpu);



		__blkg_clear_stat(s);

	}

	__blkg_clear_stat(&blkg->iostat);

}



static int blkcg_reset_stats(struct cgroup_subsys_state *css,

			     struct cftype *cftype, u64 val)

{

	struct blkcg *blkcg = css_to_blkcg(css);

	struct blkcg_gq *blkg;

	int i, cpu;

	int i;



	mutex_lock(&blkcg_pol_mutex);

	spin_lock_irq(&blkcg->lock);
@@ -634,18 +667,7 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css, 
	 * anyway.  If you get hit by a race, retry.

	 */

	hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {

		for_each_possible_cpu(cpu) {

			struct blkg_iostat_set *bis =

				per_cpu_ptr(blkg->iostat_cpu, cpu);

			memset(bis, 0, sizeof(*bis));



			/* Re-initialize the cleared blkg_iostat_set */

			u64_stats_init(&bis->sync);

			bis->blkg = blkg;

		}

		memset(&blkg->iostat, 0, sizeof(blkg->iostat));

		u64_stats_init(&blkg->iostat.sync);



		blkg_clear_stat(blkg);

		for (i = 0; i < BLKCG_MAX_POLS; i++) {

			struct blkcg_policy *pol = blkcg_policy[i];
@@ -948,16 +970,6 @@ void blkg_conf_exit(struct blkg_conf_ctx *ctx) 
}

EXPORT_SYMBOL_GPL(blkg_conf_exit);



static void blkg_iostat_set(struct blkg_iostat *dst, struct blkg_iostat *src)

{

	int i;



	for (i = 0; i < BLKG_IOSTAT_NR; i++) {

		dst->bytes[i] = src->bytes[i];

		dst->ios[i] = src->ios[i];

	}

}



static void blkg_iostat_add(struct blkg_iostat *dst, struct blkg_iostat *src)

{

	int i;