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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     Saurabh Sengar <ssengar@linux.microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Dexuan Cui <decui@microsoft.com>,
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        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Saurabh Singh Sengar <ssengar@microsoft.com>
Subject: RE: [PATCH] scsi: storvsc: Remove WQ_MEM_RECLAIM from
 storvsc_error_wq
Thread-Topic: [PATCH] scsi: storvsc: Remove WQ_MEM_RECLAIM from
 storvsc_error_wq
Thread-Index: AQHYpYCi7mFrpB9jL0m3yqafwIHdQa2e1quQ
Date:   Thu, 4 Aug 2022 14:52:00 +0000
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From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Monday, August 1, =
2022 1:28 AM
>=20
> 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:
>=20
> [   14.506347] ------------[ cut here ]------------
> [   14.506354] workqueue: WQ_MEM_RECLAIM storvsc_error_wq_0:storvsc_remov=
e_lun is flushing !WQ_MEM_RECLAIM events_freezable_power_:disk_events_workf=
n
> [   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-az=
ure #91~18.04.1-Ubuntu
> [   14.506391] Hardware name: Microsoft Corporation Virtual Machine/Virtu=
al 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 ]---
>=20
> 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(-)
>=20
> 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 =3D
>  			alloc_ordered_workqueue("storvsc_error_wq_%d",
> -						WQ_MEM_RECLAIM,
> +						0,
>  						host->host_no);
>  	if (!host_dev->handle_error_wq) {
>  		ret =3D -ENOMEM;
> --
> 1.8.3.1