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blk-stat: don't use this_cpu_ptr() in a preemptable section 

If PREEMPT_RCU is enabled, rcu_read_lock() isn't strong enough
for us to use this_cpu_ptr() in that section. Use the safer
get/put_cpu_ptr() variants instead.

Reported-by: Mike Galbraith <efault@gmx.de>
Fixes: 34dbad5d26 ("blk-stat: convert to callback-based statistics reporting")
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Jens Axboe 2017-05-09 11:39:56 -06:00
parent 340ff32167
commit d373812398
1 changed files with 10 additions and 7 deletions
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17
block/blk-stat.c
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@ -96,13 +96,16 @@ void blk_stat_add(struct request *rq)
rcu_read_lock();
list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
if (blk_stat_is_active(cb)) {
bucket = cb->bucket_fn(rq);
if (bucket < 0)
continue;
stat = &this_cpu_ptr(cb->cpu_stat)[bucket];
__blk_stat_add(stat, value);
}
if (!blk_stat_is_active(cb))
continue;
bucket = cb->bucket_fn(rq);
if (bucket < 0)
continue;
stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
__blk_stat_add(stat, value);
put_cpu_ptr(cb->cpu_stat);
}
rcu_read_unlock();
}