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authorWaiman Long <longman@redhat.com>2023-06-06 14:07:24 -0400
committerJens Axboe <axboe@kernel.dk>2023-06-07 07:51:34 -0600
commit3d2af77e31ade05ff7ccc3658c3635ec1bea0979 (patch)
tree719e78adff52ac9922e337e5c5bc7fbe169ca639 /block/blk-cgroup.c
parenta7cfa0af0c88353b4eb59db5a2a0fbe35329b3f9 (diff)
blk-cgroup: Reinit blkg_iostat_set after clearing in blkcg_reset_stats()
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 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") while the later one was introduced by commit f73316482977 ("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: 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()") Fixes: f73316482977 ("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>
Diffstat (limited to 'block/blk-cgroup.c')
-rw-r--r--block/blk-cgroup.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 1c6716f51fff..cab33bd4f252 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -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];