[dm-devel] [PATCH 1/3] scsi: avoid to quiesce sdev->request_queue two times

[Ming Lei]

For fixing queue quiesce race between driver and block layer(elevator
switch, update nr_requests, ...), we need to support concurrent quiesce
and unquiesce, which requires the two to be balanced.

blk_mq_quiesce_queue() calls blk_mq_quiesce_queue_nowait() for updating
quiesce depth and marking the flag, then scsi_internal_device_block() calls
blk_mq_quiesce_queue_nowait() two times actually.

Fix the double quiesce and keep quiesce and unquiesce balanced.

Reported-by: Yi Zhang <yi.zh...@redhat.com>
Fixes: e70feb8b3e68 ("blk-mq: support concurrent queue quiesce/unquiesce")
Signed-off-by: Ming Lei <ming....@redhat.com>
---
 drivers/scsi/scsi_lib.c | 29 ++++++++++++++---------------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 30f7d0b4eb73..51fcd46be265 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -2630,6 +2630,14 @@ scsi_target_resume(struct scsi_target *starget)
 }
 EXPORT_SYMBOL(scsi_target_resume);
 
+static int __scsi_internal_device_block_nowait(struct scsi_device *sdev)
+{
+       if (scsi_device_set_state(sdev, SDEV_BLOCK))
+               return scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
+
+       return 0;
+}
+
 /**
  * scsi_internal_device_block_nowait - try to transition to the SDEV_BLOCK 
state
  * @sdev: device to block
@@ -2646,24 +2654,16 @@ EXPORT_SYMBOL(scsi_target_resume);
  */
 int scsi_internal_device_block_nowait(struct scsi_device *sdev)
 {
-       struct request_queue *q = sdev->request_queue;
-       int err = 0;
-
-       err = scsi_device_set_state(sdev, SDEV_BLOCK);
-       if (err) {
-               err = scsi_device_set_state(sdev, SDEV_CREATED_BLOCK);
-
-               if (err)
-                       return err;
-       }
+       int ret = __scsi_internal_device_block_nowait(sdev);
 
        /*
         * The device has transitioned to SDEV_BLOCK.  Stop the
         * block layer from calling the midlayer with this device's
         * request queue.
         */
-       blk_mq_quiesce_queue_nowait(q);
-       return 0;
+       if (!ret)
+               blk_mq_quiesce_queue_nowait(sdev->request_queue);
+       return ret;
 }
 EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
 
@@ -2684,13 +2684,12 @@ EXPORT_SYMBOL_GPL(scsi_internal_device_block_nowait);
  */
 static int scsi_internal_device_block(struct scsi_device *sdev)
 {
-       struct request_queue *q = sdev->request_queue;
        int err;
 
        mutex_lock(&sdev->state_mutex);
-       err = scsi_internal_device_block_nowait(sdev);
+       err = __scsi_internal_device_block_nowait(sdev);
        if (err == 0)
-               blk_mq_quiesce_queue(q);
+               blk_mq_quiesce_queue(sdev->request_queue);
        mutex_unlock(&sdev->state_mutex);
 
        return err;
-- 
2.31.1

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