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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>
master
Hong Zhiguo 8 years ago
committed by Jens Axboe
parent
commit
2c575026fa
  1. 8
      block/blk-cgroup.h

8
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;
}

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