From: Martin Wilck <mwilck@xxxxxxxx> scsi_stop_queue() has just two callers, one with and one without "nowait". As blk_mq_quiesce_queue() comes down to blk_mq_quiesce_queue_nowait() followed by blk_mq_wait_quiesce_done(), we might as well open-code this in scsi_device_block(). Also, add a comment explaining why blk_mq_quiesce_queue_nowait() must be called with the state_mutex held, see https://lore.kernel.org/linux-scsi/3b8b13bf-a458-827a-b916-07d7eee8ae00@xxxxxxx/. Signed-off-by: Martin Wilck <mwilck@xxxxxxxx> --- drivers/scsi/scsi_lib.c | 32 ++++++++++++++++---------------- 1 file changed, 16 insertions(+), 16 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 69fb7a9d8883..b4cc1501dc36 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2731,24 +2731,16 @@ void scsi_start_queue(struct scsi_device *sdev) blk_mq_unquiesce_queue(sdev->request_queue); } -static void scsi_stop_queue(struct scsi_device *sdev, bool nowait) +static void scsi_stop_queue(struct scsi_device *sdev) { /* * The atomic variable of ->queue_stopped covers that * blk_mq_quiesce_queue* is balanced with blk_mq_unquiesce_queue. * - * However, we still need to wait until quiesce is done - * in case that queue has been stopped. + * After return, we still need to wait until quiesce is done. */ - if (!cmpxchg(&sdev->queue_stopped, 0, 1)) { - if (nowait) - blk_mq_quiesce_queue_nowait(sdev->request_queue); - else - blk_mq_quiesce_queue(sdev->request_queue); - } else { - if (!nowait) - blk_mq_wait_quiesce_done(sdev->request_queue->tag_set); - } + if (!cmpxchg(&sdev->queue_stopped, 0, 1)) + blk_mq_quiesce_queue_nowait(sdev->request_queue); } /** @@ -2775,7 +2767,7 @@ int scsi_internal_device_block_nowait(struct scsi_device *sdev) * request queue. */ if (!ret) - scsi_stop_queue(sdev, true); + scsi_stop_queue(sdev); return ret; } EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait); @@ -2800,9 +2792,17 @@ static void scsi_device_block(struct scsi_device *sdev, void *data) mutex_lock(&sdev->state_mutex); err = __scsi_internal_device_block_nowait(sdev); - if (err == 0) - scsi_stop_queue(sdev, false); - mutex_unlock(&sdev->state_mutex); + if (err == 0) { + /* + * scsi_stop_queue() must be called with the state_mutex + * held. Otherwise a simultaneous scsi_start_queue() call + * might unquiesce the queue before we quiesce it. + */ + scsi_stop_queue(sdev); + mutex_unlock(&sdev->state_mutex); + blk_mq_wait_quiesce_done(sdev->request_queue->tag_set); + } else + mutex_unlock(&sdev->state_mutex); WARN_ONCE(err, "__scsi_internal_device_block_nowait(%s) failed: err = %d\n", dev_name(&sdev->sdev_gendev), err); -- 2.40.1
