| Message ID | ba8ddc16-b709-e7fb-1120-b6e1bd393540@sandisk.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 09/26/2016 08:26 PM, Bart Van Assche wrote: > Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() > calls have stopped before setting the "queue stopped" flag. This > allows to remove the "queue stopped" test from dm_mq_queue_rq() and > dm_mq_requeue_request(). This patch fixes a race condition because > dm_mq_queue_rq() is called without holding the queue lock and hence > BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is > in progress. > > Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> > Cc: Mike Snitzer <snitzer@redhat.com> > --- > drivers/md/dm-rq.c | 14 +++----------- > 1 file changed, 3 insertions(+), 11 deletions(-) > Reviewed-by: Hannes Reinecke <hare@suse.com> Cheers, Hannes
On Mon, Sep 26, 2016 at 11:26:50AM -0700, Bart Van Assche wrote: > Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() > calls have stopped before setting the "queue stopped" flag. This > allows to remove the "queue stopped" test from dm_mq_queue_rq() and > dm_mq_requeue_request(). This patch fixes a race condition because > dm_mq_queue_rq() is called without holding the queue lock and hence > BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is > in progress. > > Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> > Cc: Mike Snitzer <snitzer@redhat.com> > --- Looks good, Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 182b679..1b7a65e 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -116,9 +116,12 @@ static void dm_mq_stop_queue(struct request_queue *q) queue_flag_set(QUEUE_FLAG_STOPPED, q); spin_unlock_irqrestore(q->queue_lock, flags); + /* Wait until dm_mq_queue_rq() has finished. */ + blk_quiesce_queue(q); /* Avoid that requeuing could restart the queue. */ blk_mq_cancel_requeue_work(q); blk_mq_stop_hw_queues(q); + blk_resume_queue(q); } void dm_stop_queue(struct request_queue *q) @@ -901,17 +904,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, dm_put_live_table(md, srcu_idx); } - /* - * On suspend dm_stop_queue() handles stopping the blk-mq - * request_queue BUT: even though the hw_queues are marked - * BLK_MQ_S_STOPPED at that point there is still a race that - * is allowing block/blk-mq.c to call ->queue_rq against a - * hctx that it really shouldn't. The following check guards - * against this rarity (albeit _not_ race-free). - */ - if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))) - return BLK_MQ_RQ_QUEUE_BUSY; - if (ti->type->busy && ti->type->busy(ti)) return BLK_MQ_RQ_QUEUE_BUSY;
Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() calls have stopped before setting the "queue stopped" flag. This allows to remove the "queue stopped" test from dm_mq_queue_rq() and dm_mq_requeue_request(). This patch fixes a race condition because dm_mq_queue_rq() is called without holding the queue lock and hence BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is in progress. Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com> Cc: Mike Snitzer <snitzer@redhat.com> --- drivers/md/dm-rq.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-)