Update of blkg_stat and blkg_rwstat may happen in bh context.

While u64_stats_fetch_retry is only preempt_disable on 32bit
UP system. This is not enough to avoid preemption by bh and
may read strange 64 bit value.

Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1610b22..86154ea 100644 (file)
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -435,9 +435,9 @@ static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
        uint64_t v;
 
        do {
-               start = u64_stats_fetch_begin(&stat->syncp);
+               start = u64_stats_fetch_begin_bh(&stat->syncp);
                v = stat->cnt;
-       } while (u64_stats_fetch_retry(&stat->syncp, start));
+       } while (u64_stats_fetch_retry_bh(&stat->syncp, start));
 
        return v;
 }
@@ -508,9 +508,9 @@ static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
        struct blkg_rwstat tmp;
 
        do {
-               start = u64_stats_fetch_begin(&rwstat->syncp);
+               start = u64_stats_fetch_begin_bh(&rwstat->syncp);
                tmp = *rwstat;
-       } while (u64_stats_fetch_retry(&rwstat->syncp, start));
+       } while (u64_stats_fetch_retry_bh(&rwstat->syncp, start));
 
        return tmp;
 }