[PATCH 4/8] ublk: reset the FETCH round in release also without a disk

[Ming Lei <tom.leiming@gmail.com>]

The release of /dev/ublkcN resets the queues only when the device has a
disk. Without one it skips ublk_reset_ch_dev():

  server fetches, never starts;         old server exits
  or STOP_DEV removed the disk           release: no disk → skip reset
                                         ios stay ACTIVE / CANCELED,
                                         nr_io_ready stays full
  new server opens /dev/ublkcN           FETCH: -EBUSY (still ready), or
                                         -EINVAL after a partial round
                                         → the device can only be deleted

All uring_cmds are done when the release work runs, with or without a
disk, so the reset is safe either way. Do it in both cases. Then a new
server can fetch and start the device again, as the STOP_DEV entry in
Documentation/block/ublk.rst says ("ublk device is ready for the new
process").

Fixes: 82a8a30c581b ("ublk: improve detection and handling of ublk server exit")
Cc: stable@vger.kernel.org
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 drivers/block/ublk_drv.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 5e37b8e9d9ac..8bf0739539c0 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -2551,12 +2551,13 @@ static void ublk_ch_release_work_fn(struct work_struct *work)
 	}
 
 	/*
-	 * disk isn't attached yet, either device isn't live, or it has
-	 * been removed already, so we needn't to do anything
+	 * No disk: the device isn't live, or it has been removed already.
+	 * There are no requests to abort, but the round still has to be
+	 * reset, so that a new server can fetch and start the device.
 	 */
 	disk = ublk_get_disk(ub);
 	if (!disk)
-		goto out;
+		goto reset;
 
 	/*
 	 * All uring_cmd are done now, so abort any request outstanding to
@@ -2617,10 +2618,9 @@ static void ublk_ch_release_work_fn(struct work_struct *work)
 unlock:
 	mutex_unlock(&ub->mutex);
 	ublk_put_disk(disk);
-
+reset:
 	/* all uring_cmd has been done now, reset device & ubq */
 	ublk_reset_ch_dev(ub);
-out:
 	clear_bit(UB_STATE_OPEN, &ub->state);
 
 	/* put the reference grabbed in ublk_ch_release() */
-- 
2.55.0