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 <[email protected]> Acked-by: Tejun Heo <[email protected]> Cc: [email protected] Signed-off-by: Jens Axboe <[email protected]>
torvalds · Nov 20, 2013 · 2c57502 · 2c57502
1 parent 82023bb
commit 2c57502
Showing 1 changed file with 4 additions and 4 deletions.
diff --git 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;
 }