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

Michael Kelley (LINUX)
2022-08-04T15:07:54Z

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