[PATCH] scsi: storvsc: Remove WQ_MEM_RECLAIM from storvsc_error_wq

[PATCH] scsi: storvsc: Remove WQ_MEM_RECLAIM from storvsc_error_wq

[Saurabh Sengar]

storvsc_error_wq workqueue should not be marked as WQ_MEM_RECLAIM
as it's doesn't need to make forward progress under memory pressure.
Marking this workqueue as WQ_MEM_RECLAIM may cause deadlock while
flushing a non-WQ_MEM_RECLAIM workqueue.
In the current state it causes the following warning:

[   14.506347] ------------[ cut here ]------------
[   14.506354] workqueue: WQ_MEM_RECLAIM storvsc_error_wq_0:storvsc_remove_lun is flushing !WQ_MEM_RECLAIM events_freezable_power_:disk_events_workfn
[   14.506360] WARNING: CPU: 0 PID: 8 at <-snip->kernel/workqueue.c:2623 check_flush_dependency+0xb5/0x130
[   14.506390] CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.4.0-1086-azure #91~18.04.1-Ubuntu
[   14.506391] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 05/09/2022
[   14.506393] Workqueue: storvsc_error_wq_0 storvsc_remove_lun
[   14.506395] RIP: 0010:check_flush_dependency+0xb5/0x130
		<-snip->
[   14.506408] Call Trace:
[   14.506412]  __flush_work+0xf1/0x1c0
[   14.506414]  __cancel_work_timer+0x12f/0x1b0
[   14.506417]  ? kernfs_put+0xf0/0x190
[   14.506418]  cancel_delayed_work_sync+0x13/0x20
[   14.506420]  disk_block_events+0x78/0x80
[   14.506421]  del_gendisk+0x3d/0x2f0
[   14.506423]  sr_remove+0x28/0x70
[   14.506427]  device_release_driver_internal+0xef/0x1c0
[   14.506428]  device_release_driver+0x12/0x20
[   14.506429]  bus_remove_device+0xe1/0x150
[   14.506431]  device_del+0x167/0x380
[   14.506432]  __scsi_remove_device+0x11d/0x150
[   14.506433]  scsi_remove_device+0x26/0x40
[   14.506434]  storvsc_remove_lun+0x40/0x60
[   14.506436]  process_one_work+0x209/0x400
[   14.506437]  worker_thread+0x34/0x400
[   14.506439]  kthread+0x121/0x140
[   14.506440]  ? process_one_work+0x400/0x400
[   14.506441]  ? kthread_park+0x90/0x90
[   14.506443]  ret_from_fork+0x35/0x40
[   14.506445] ---[ end trace 2d9633159fdc6ee7 ]---

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
 drivers/scsi/storvsc_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
index fe000da..8ced292 100644
--- a/drivers/scsi/storvsc_drv.c
+++ b/drivers/scsi/storvsc_drv.c
@@ -2012,7 +2012,7 @@ static int storvsc_probe(struct hv_device *device,
 	 */
 	host_dev->handle_error_wq =
 			alloc_ordered_workqueue("storvsc_error_wq_%d",
-						WQ_MEM_RECLAIM,
+						0,
 						host->host_no);
 	if (!host_dev->handle_error_wq) {
 		ret = -ENOMEM;
-- 
1.8.3.1

RE: [PATCH] scsi: storvsc: Remove WQ_MEM_RECLAIM from storvsc_error_wq

[Michael Kelley (LINUX)]

From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Monday, August 1, 2022 1:28 AM
> 
> storvsc_error_wq workqueue should not be marked as WQ_MEM_RECLAIM
> as it's doesn't need to make forward progress under memory pressure.

s/it's/it/

> Marking this workqueue as WQ_MEM_RECLAIM may cause deadlock while
> flushing a non-WQ_MEM_RECLAIM workqueue.
> In the current state it causes the following warning:
> 
> [   14.506347] ------------[ cut here ]------------
> [   14.506354] workqueue: WQ_MEM_RECLAIM storvsc_error_wq_0:storvsc_remove_lun is flushing !WQ_MEM_RECLAIM events_freezable_power_:disk_events_workfn
> [   14.506360] WARNING: CPU: 0 PID: 8 at <-snip->kernel/workqueue.c:2623 check_flush_dependency+0xb5/0x130
> [   14.506390] CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.4.0-1086-azure #91~18.04.1-Ubuntu
> [   14.506391] Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 05/09/2022
> [   14.506393] Workqueue: storvsc_error_wq_0 storvsc_remove_lun
> [   14.506395] RIP: 0010:check_flush_dependency+0xb5/0x130
> 		<-snip->
> [   14.506408] Call Trace:
> [   14.506412]  __flush_work+0xf1/0x1c0
> [   14.506414]  __cancel_work_timer+0x12f/0x1b0
> [   14.506417]  ? kernfs_put+0xf0/0x190
> [   14.506418]  cancel_delayed_work_sync+0x13/0x20
> [   14.506420]  disk_block_events+0x78/0x80
> [   14.506421]  del_gendisk+0x3d/0x2f0
> [   14.506423]  sr_remove+0x28/0x70
> [   14.506427]  device_release_driver_internal+0xef/0x1c0
> [   14.506428]  device_release_driver+0x12/0x20
> [   14.506429]  bus_remove_device+0xe1/0x150
> [   14.506431]  device_del+0x167/0x380
> [   14.506432]  __scsi_remove_device+0x11d/0x150
> [   14.506433]  scsi_remove_device+0x26/0x40
> [   14.506434]  storvsc_remove_lun+0x40/0x60
> [   14.506436]  process_one_work+0x209/0x400
> [   14.506437]  worker_thread+0x34/0x400
> [   14.506439]  kthread+0x121/0x140
> [   14.506440]  ? process_one_work+0x400/0x400
> [   14.506441]  ? kthread_park+0x90/0x90
> [   14.506443]  ret_from_fork+0x35/0x40
> [   14.506445] ---[ end trace 2d9633159fdc6ee7 ]---
> 
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>

This should have a "Fixes:" tag for commit 436ad9413353 where
this workqueue was introduced.

Michael

> ---
>  drivers/scsi/storvsc_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> index fe000da..8ced292 100644
> --- a/drivers/scsi/storvsc_drv.c
> +++ b/drivers/scsi/storvsc_drv.c
> @@ -2012,7 +2012,7 @@ static int storvsc_probe(struct hv_device *device,
>  	 */
>  	host_dev->handle_error_wq =
>  			alloc_ordered_workqueue("storvsc_error_wq_%d",
> -						WQ_MEM_RECLAIM,
> +						0,
>  						host->host_no);
>  	if (!host_dev->handle_error_wq) {
>  		ret = -ENOMEM;
> --
> 1.8.3.1