[PATCH v4 0/2] scsi: virtio_scsi: move INIT_WORK calls to virtscsi_probe

[Joshua Daley <jdaley@linux.ibm.com>]

TITLE CHANGED! Original series title:
"scsi: virtio_scsi: move INIT_WORK calls to virtscsi_init"
Previous version:
https://lore.kernel.org/linux-scsi/4a93583c-47a1-4700-a7bb-da75fbd231dc@linux.ibm.com/T/#t

Changelog v3 -> v4:

[PATCH v3 1/3] scsi: virtio_scsi: kick event_list unconditionally
-> [PATCH v4 2/2] scsi: virtio_scsi: kick event_list unconditionally
    - this patch now comes after moving the INIT_WORK calls, to address bisection concerns:
      https://lore.kernel.org/linux-scsi/4a93583c-47a1-4700-a7bb-da75fbd231dc@linux.ibm.com/
    - the code changes are a bit different given that the INIT_WORK calls are now moved into
      virtscsi_probe(), but the concept is the same.

[PATCH v3 2/3] scsi: virtio_scsi: move INIT_WORK calls to virtscsi_init
-> [PATCH v4 1/2] scsi: virtio_scsi: move INIT_WORK calls to virtscsi_probe
   - the INIT_WORK calls are now moved to virtscsi_probe() to address concerns
     with suspend/resume. The title of the series is changed to reflect this.

[PATCH v3 3/3] scsi: virtio_scsi: remove unnecessary fn declaration
- squashed into [PATCH v4 1/2]

-----

v3 cover letter:

Changelog v2 -> v3:

- switched the order of patches 2 & 3 to fix compilation error.
- added reviewed-by tags.

-----

v2 cover letter:

Changelog v1 -> v2:

- Added 2 additional patches:
  - [PATCH v2 1/3] scsi: virtio_scsi: kick event_list unconditionally
    - Removes the conditions surrounding event_list operations (suggested by Stefan Hajnoczi [<stefanha@redhat.com>](mailto:stefanha@redhat.com))
  - [PATCH v2 2/3] scsi: virtio_scsi: remove unnecessary fn declaration
    - Removes virtscsi_handle_event() prototype (suggested by Eric Farman [<farman@linux.ibm.com>](mailto:farman@linux.ibm.com))

- [PATCH 1/1] -> [PATCH v2 3/3] scsi: virtio_scsi: move INIT_WORK calls to virtscsi_init
  - Removed the condition surrounding INIT_WORK calls

-----

v1 cover letter:

This patch avoids a kernel warning that may occur if a virtio_scsi
controller is detached immediately following a disk detach. See the
commit message for details. The following are instructions to
produce the warning (without the proposed patch).

Timing matters--if all event work items call INIT_WORK before they are
flushed by cancel_work_sync, then the warning will not occur.

The warning will occur consistently if a sleep is added in
virtscsi_kick_event before the INIT_WORK call, like so:

#include <linux/delay.h>

static int virtscsi_kick_event(struct virtio_scsi *vscsi,
			       struct virtio_scsi_event_node *event_node)
{
    int err;
    struct scatterlist sg;
    unsigned long flags;

 -> msleep(1000);
    INIT_WORK(&event_node->work, virtscsi_handle_event);
	
    ...
}

Then, just detach a disk and its controller in quick succession:

virsh detach-device --domain <domain> disk.xml; \
virsh detach-device --domain <domain> controller.xml

where disk.xml and controller.xml are text files containing the XML
of the disk and controller.

Or, with the libvirt python module:

domain.detachDevice(str(disk_xml))
domain.detachDevice(str(controller_xml))

Joshua Daley (2):
  scsi: virtio_scsi: move INIT_WORK calls to virtscsi_probe
  scsi: virtio_scsi: kick event_list unconditionally

 drivers/scsi/virtio_scsi.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

-- 
2.34.1