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Commit 2c575026 authored by Hong Zhiguo's avatar Hong Zhiguo Committed by Jens Axboe
Browse files

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: default avatarHong Zhiguo <zhiguohong@tencent.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Cc: stable@kernel.org
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 82023bb7

block/blk-cgroup.h

+4 −4
Original line number Diff line number Diff line
@@ -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;

}