[PATCH 6.9 225/374] blk-cgroup: fix list corruption from resetting io stat

Greg Kroah-Hartman
2024-06-06T14:10:41Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 6da6680632792709cecf2b006f2fe3ca7857e791 ]

Since commit 3b8cc6298724 ("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: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20240515013157.443672-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-cgroup.c | 58 ++++++++++++++++++++++++++++------------------
1 file changed, 35 insertions(+), 23 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 059467086b131..86752b1652b5b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -619,12 +619,45 @@ 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);
@@ -635,18 +668,7 @@ 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];

@@ -949,16 +971,6 @@ 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;
--
2.43.0