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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.

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commit 2c575026fae6e63771bd2a4c1d407214a8096a89 upstream.

Signed-off-by: Hong Zhiguo <zhiguohong@tencent.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hong Zhiguo 2013-11-20 10:35:05 -07:00 committed by Greg Kroah-Hartman
parent c523480797
commit 950cda7f8e
1 changed files with 4 additions and 4 deletions
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8
block/blk-cgroup.h
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@ -399,9 +399,9 @@ 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;
}
@ -467,9 +467,9 @@ 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;
}