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blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()

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When blkg_alloc() is called to allocate a blkcg_gq structure
with the associated blkg_iostat_set's, there are 2 fields within
blkg_iostat_set that requires proper initialization - blkg & sync.
The former field was introduced by commit 3b8cc62987 ("blk-cgroup:
Optimize blkcg_rstat_flush()") while the later one was introduced by
commit f733164829 ("blk-cgroup: reimplement basic IO stats using
cgroup rstat").

Unfortunately those fields in the blkg_iostat_set's are not properly
re-initialized when they are cleared in v1's blkcg_reset_stats(). This
can lead to a kernel panic due to NULL pointer access of the blkg
pointer. The missing initialization of sync is less problematic and
can be a problem in a debug kernel due to missing lockdep initialization.

Fix these problems by re-initializing them after memory clearing.

Fixes: 3b8cc62987 ("blk-cgroup: Optimize blkcg_rstat_flush()")
Fixes: f733164829 ("blk-cgroup: reimplement basic IO stats using cgroup rstat")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230606180724.2455066-1-longman@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Waiman Long 2023-06-06 14:07:24 -04:00 committed by Jens Axboe
parent a7cfa0af0c
commit 3d2af77e31
1 changed files with 5 additions and 0 deletions
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5
block/blk-cgroup.c
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@ -610,8 +610,13 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
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);
for (i = 0; i < BLKCG_MAX_POLS; i++) {
struct blkcg_policy *pol = blkcg_policy[i];