[PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Suwan Kim]

If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
despite the failure.

[    1.890468] ------------[ cut here ]------------
[    1.890776] WARNING: CPU: 2 PID: 122 at block/blk-mq.c:1143
blk_mq_start_request+0x8a/0xe0
[    1.891045] Modules linked in:
[    1.891250] CPU: 2 PID: 122 Comm: journal-offline Not tainted 5.19.0+ #44
[    1.891504] Hardware name: ChromiumOS crosvm, BIOS 0
[    1.891739] RIP: 0010:blk_mq_start_request+0x8a/0xe0
[    1.891961] Code: 12 80 74 22 48 8b 4b 10 8b 89 64 01 00 00 8b 53
20 83 fa ff 75 08 ba 00 00 00 80 0b 53 24 c1 e1 10 09 d1 89 48 34 5b
41 5e c3 <0f> 0b eb b8 65 8b 05 2b 39 b6 7e 89 c0 48 0f a3 05 39 77 5b
01 0f
[    1.892443] RSP: 0018:ffffc900002777b0 EFLAGS: 00010202
[    1.892673] RAX: 0000000000000000 RBX: ffff888004bc0000 RCX: 0000000000000000
[    1.892952] RDX: 0000000000000000 RSI: ffff888003d7c200 RDI: ffff888004bc0000
[    1.893228] RBP: 0000000000000000 R08: 0000000000000001 R09: ffff888004bc0100
[    1.893506] R10: ffffffffffffffff R11: ffffffff8185ca10 R12: ffff888004bc0000
[    1.893797] R13: ffffc90000277900 R14: ffff888004ab2340 R15: ffff888003d86e00
[    1.894060] FS:  00007ffa143a4640(0000) GS:ffff88807dd00000(0000)
knlGS:0000000000000000
[    1.894412] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    1.894682] CR2: 00005648577d9088 CR3: 00000000053da004 CR4: 0000000000170ee0
[    1.894953] Call Trace:
[    1.895139]  <TASK>
[    1.895303]  virtblk_prep_rq+0x1e5/0x280
[    1.895509]  virtio_queue_rq+0x5c/0x310
[    1.895710]  ? virtqueue_add_sgs+0x95/0xb0
[    1.895905]  ? _raw_spin_unlock_irqrestore+0x16/0x30
[    1.896133]  ? virtio_queue_rqs+0x340/0x390
[    1.896453]  ? sbitmap_get+0xfa/0x220
[    1.896678]  __blk_mq_issue_directly+0x41/0x180
[    1.896906]  blk_mq_plug_issue_direct+0xd8/0x2c0
[    1.897115]  blk_mq_flush_plug_list+0x115/0x180
[    1.897342]  blk_add_rq_to_plug+0x51/0x130
[    1.897543]  blk_mq_submit_bio+0x3a1/0x570
[    1.897750]  submit_bio_noacct_nocheck+0x418/0x520
[    1.897985]  ? submit_bio_noacct+0x1e/0x260
[    1.897989]  ext4_bio_write_page+0x222/0x420
[    1.898000]  mpage_process_page_bufs+0x178/0x1c0
[    1.899451]  mpage_prepare_extent_to_map+0x2d2/0x440
[    1.899603]  ext4_writepages+0x495/0x1020
[    1.899733]  do_writepages+0xcb/0x220
[    1.899871]  ? __seccomp_filter+0x171/0x7e0
[    1.900006]  file_write_and_wait_range+0xcd/0xf0
[    1.900167]  ext4_sync_file+0x72/0x320
[    1.900308]  __x64_sys_fsync+0x66/0xa0
[    1.900449]  do_syscall_64+0x31/0x50
[    1.900595]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
[    1.900747] RIP: 0033:0x7ffa16ec96ea
[    1.900883] Code: b8 4a 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3
48 83 ec 18 89 7c 24 0c e8 e3 02 f8 ff 8b 7c 24 0c 89 c2 b8 4a 00 00
00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 43 03 f8 ff 8b
44 24
[    1.901302] RSP: 002b:00007ffa143a3ac0 EFLAGS: 00000293 ORIG_RAX:
000000000000004a
[    1.901499] RAX: ffffffffffffffda RBX: 0000560277ec6fe0 RCX: 00007ffa16ec96ea
[    1.901696] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000016
[    1.901884] RBP: 0000560277ec5910 R08: 0000000000000000 R09: 00007ffa143a4640
[    1.902082] R10: 00007ffa16e4d39e R11: 0000000000000293 R12: 00005602773f59e0
[    1.902459] R13: 0000000000000000 R14: 00007fffbfc007ff R15: 00007ffa13ba4000
[    1.902763]  </TASK>
[    1.902877] ---[ end trace 0000000000000000 ]---

To avoid calling blk_mq_start_request() twice, This patch moves the
execution of blk_mq_start_request() to the end of virtblk_prep_rq().
And instead of requeuing failed request to plug list in the error path of
virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
on the next trial.

Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
Reported-by: Alexandre Courbot <acourbot@chromium.org>
Tested-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
---
v1 -> v2
 - Call blk_mq_start_request() after virtblk_add_req() can break the timestamp.
   So move virtblk_add_req() before blk_mq_start_request().
 - Use blk_mq_requeue_request() instead of requeuing failed request to plug list
   if virtblk_add_req() fails within virtblk_add_req_batch(). 


 drivers/block/virtio_blk.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 30255fcaf181..dd9a05174726 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -322,14 +322,14 @@ static blk_status_t virtblk_prep_rq(struct blk_mq_hw_ctx *hctx,
 	if (unlikely(status))
 		return status;
 
-	blk_mq_start_request(req);
-
 	vbr->sg_table.nents = virtblk_map_data(hctx, req, vbr);
 	if (unlikely(vbr->sg_table.nents < 0)) {
 		virtblk_cleanup_cmd(req);
 		return BLK_STS_RESOURCE;
 	}
 
+	blk_mq_start_request(req);
+
 	return BLK_STS_OK;
 }
 
@@ -391,8 +391,7 @@ static bool virtblk_prep_rq_batch(struct request *req)
 }
 
 static bool virtblk_add_req_batch(struct virtio_blk_vq *vq,
-					struct request **rqlist,
-					struct request **requeue_list)
+					struct request **rqlist)
 {
 	unsigned long flags;
 	int err;
@@ -408,7 +407,7 @@ static bool virtblk_add_req_batch(struct virtio_blk_vq *vq,
 		if (err) {
 			virtblk_unmap_data(req, vbr);
 			virtblk_cleanup_cmd(req);
-			rq_list_add(requeue_list, req);
+			blk_mq_requeue_request(req, true);
 		}
 	}
 
@@ -436,7 +435,7 @@ static void virtio_queue_rqs(struct request **rqlist)
 
 		if (!next || req->mq_hctx != next->mq_hctx) {
 			req->rq_next = NULL;
-			kick = virtblk_add_req_batch(vq, rqlist, &requeue_list);
+			kick = virtblk_add_req_batch(vq, rqlist);
 			if (kick)
 				virtqueue_notify(vq->vq);
 
-- 
2.26.3

Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Stefan Hajnoczi]

[-- Attachment #1.1: Type: text/plain, Size: 5167 bytes --]

On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> despite the failure.
> 
> [    1.890468] ------------[ cut here ]------------
> [    1.890776] WARNING: CPU: 2 PID: 122 at block/blk-mq.c:1143
> blk_mq_start_request+0x8a/0xe0
> [    1.891045] Modules linked in:
> [    1.891250] CPU: 2 PID: 122 Comm: journal-offline Not tainted 5.19.0+ #44
> [    1.891504] Hardware name: ChromiumOS crosvm, BIOS 0
> [    1.891739] RIP: 0010:blk_mq_start_request+0x8a/0xe0
> [    1.891961] Code: 12 80 74 22 48 8b 4b 10 8b 89 64 01 00 00 8b 53
> 20 83 fa ff 75 08 ba 00 00 00 80 0b 53 24 c1 e1 10 09 d1 89 48 34 5b
> 41 5e c3 <0f> 0b eb b8 65 8b 05 2b 39 b6 7e 89 c0 48 0f a3 05 39 77 5b
> 01 0f
> [    1.892443] RSP: 0018:ffffc900002777b0 EFLAGS: 00010202
> [    1.892673] RAX: 0000000000000000 RBX: ffff888004bc0000 RCX: 0000000000000000
> [    1.892952] RDX: 0000000000000000 RSI: ffff888003d7c200 RDI: ffff888004bc0000
> [    1.893228] RBP: 0000000000000000 R08: 0000000000000001 R09: ffff888004bc0100
> [    1.893506] R10: ffffffffffffffff R11: ffffffff8185ca10 R12: ffff888004bc0000
> [    1.893797] R13: ffffc90000277900 R14: ffff888004ab2340 R15: ffff888003d86e00
> [    1.894060] FS:  00007ffa143a4640(0000) GS:ffff88807dd00000(0000)
> knlGS:0000000000000000
> [    1.894412] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.894682] CR2: 00005648577d9088 CR3: 00000000053da004 CR4: 0000000000170ee0
> [    1.894953] Call Trace:
> [    1.895139]  <TASK>
> [    1.895303]  virtblk_prep_rq+0x1e5/0x280
> [    1.895509]  virtio_queue_rq+0x5c/0x310
> [    1.895710]  ? virtqueue_add_sgs+0x95/0xb0
> [    1.895905]  ? _raw_spin_unlock_irqrestore+0x16/0x30
> [    1.896133]  ? virtio_queue_rqs+0x340/0x390
> [    1.896453]  ? sbitmap_get+0xfa/0x220
> [    1.896678]  __blk_mq_issue_directly+0x41/0x180
> [    1.896906]  blk_mq_plug_issue_direct+0xd8/0x2c0
> [    1.897115]  blk_mq_flush_plug_list+0x115/0x180
> [    1.897342]  blk_add_rq_to_plug+0x51/0x130
> [    1.897543]  blk_mq_submit_bio+0x3a1/0x570
> [    1.897750]  submit_bio_noacct_nocheck+0x418/0x520
> [    1.897985]  ? submit_bio_noacct+0x1e/0x260
> [    1.897989]  ext4_bio_write_page+0x222/0x420
> [    1.898000]  mpage_process_page_bufs+0x178/0x1c0
> [    1.899451]  mpage_prepare_extent_to_map+0x2d2/0x440
> [    1.899603]  ext4_writepages+0x495/0x1020
> [    1.899733]  do_writepages+0xcb/0x220
> [    1.899871]  ? __seccomp_filter+0x171/0x7e0
> [    1.900006]  file_write_and_wait_range+0xcd/0xf0
> [    1.900167]  ext4_sync_file+0x72/0x320
> [    1.900308]  __x64_sys_fsync+0x66/0xa0
> [    1.900449]  do_syscall_64+0x31/0x50
> [    1.900595]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [    1.900747] RIP: 0033:0x7ffa16ec96ea
> [    1.900883] Code: b8 4a 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3
> 48 83 ec 18 89 7c 24 0c e8 e3 02 f8 ff 8b 7c 24 0c 89 c2 b8 4a 00 00
> 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 43 03 f8 ff 8b
> 44 24
> [    1.901302] RSP: 002b:00007ffa143a3ac0 EFLAGS: 00000293 ORIG_RAX:
> 000000000000004a
> [    1.901499] RAX: ffffffffffffffda RBX: 0000560277ec6fe0 RCX: 00007ffa16ec96ea
> [    1.901696] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000016
> [    1.901884] RBP: 0000560277ec5910 R08: 0000000000000000 R09: 00007ffa143a4640
> [    1.902082] R10: 00007ffa16e4d39e R11: 0000000000000293 R12: 00005602773f59e0
> [    1.902459] R13: 0000000000000000 R14: 00007fffbfc007ff R15: 00007ffa13ba4000
> [    1.902763]  </TASK>
> [    1.902877] ---[ end trace 0000000000000000 ]---
> 
> To avoid calling blk_mq_start_request() twice, This patch moves the
> execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> And instead of requeuing failed request to plug list in the error path of
> virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> on the next trial.
> 
> Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> Reported-by: Alexandre Courbot <acourbot@chromium.org>
> Tested-by: Alexandre Courbot <acourbot@chromium.org>
> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> ---
> v1 -> v2
>  - Call blk_mq_start_request() after virtblk_add_req() can break the timestamp.
>    So move virtblk_add_req() before blk_mq_start_request().
>  - Use blk_mq_requeue_request() instead of requeuing failed request to plug list
>    if virtblk_add_req() fails within virtblk_add_req_batch(). 
> 
> 
>  drivers/block/virtio_blk.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Thanks for solving the timestamp issue. I'm not familiar enough which
blk_mq_requeue_request() to confirm this version is correct, but from
the virtio_blk perspective:

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

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[-- Attachment #2: Type: text/plain, Size: 183 bytes --]

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Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Stefan Hajnoczi]

[-- Attachment #1: Type: text/plain, Size: 5167 bytes --]

On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> despite the failure.
> 
> [    1.890468] ------------[ cut here ]------------
> [    1.890776] WARNING: CPU: 2 PID: 122 at block/blk-mq.c:1143
> blk_mq_start_request+0x8a/0xe0
> [    1.891045] Modules linked in:
> [    1.891250] CPU: 2 PID: 122 Comm: journal-offline Not tainted 5.19.0+ #44
> [    1.891504] Hardware name: ChromiumOS crosvm, BIOS 0
> [    1.891739] RIP: 0010:blk_mq_start_request+0x8a/0xe0
> [    1.891961] Code: 12 80 74 22 48 8b 4b 10 8b 89 64 01 00 00 8b 53
> 20 83 fa ff 75 08 ba 00 00 00 80 0b 53 24 c1 e1 10 09 d1 89 48 34 5b
> 41 5e c3 <0f> 0b eb b8 65 8b 05 2b 39 b6 7e 89 c0 48 0f a3 05 39 77 5b
> 01 0f
> [    1.892443] RSP: 0018:ffffc900002777b0 EFLAGS: 00010202
> [    1.892673] RAX: 0000000000000000 RBX: ffff888004bc0000 RCX: 0000000000000000
> [    1.892952] RDX: 0000000000000000 RSI: ffff888003d7c200 RDI: ffff888004bc0000
> [    1.893228] RBP: 0000000000000000 R08: 0000000000000001 R09: ffff888004bc0100
> [    1.893506] R10: ffffffffffffffff R11: ffffffff8185ca10 R12: ffff888004bc0000
> [    1.893797] R13: ffffc90000277900 R14: ffff888004ab2340 R15: ffff888003d86e00
> [    1.894060] FS:  00007ffa143a4640(0000) GS:ffff88807dd00000(0000)
> knlGS:0000000000000000
> [    1.894412] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.894682] CR2: 00005648577d9088 CR3: 00000000053da004 CR4: 0000000000170ee0
> [    1.894953] Call Trace:
> [    1.895139]  <TASK>
> [    1.895303]  virtblk_prep_rq+0x1e5/0x280
> [    1.895509]  virtio_queue_rq+0x5c/0x310
> [    1.895710]  ? virtqueue_add_sgs+0x95/0xb0
> [    1.895905]  ? _raw_spin_unlock_irqrestore+0x16/0x30
> [    1.896133]  ? virtio_queue_rqs+0x340/0x390
> [    1.896453]  ? sbitmap_get+0xfa/0x220
> [    1.896678]  __blk_mq_issue_directly+0x41/0x180
> [    1.896906]  blk_mq_plug_issue_direct+0xd8/0x2c0
> [    1.897115]  blk_mq_flush_plug_list+0x115/0x180
> [    1.897342]  blk_add_rq_to_plug+0x51/0x130
> [    1.897543]  blk_mq_submit_bio+0x3a1/0x570
> [    1.897750]  submit_bio_noacct_nocheck+0x418/0x520
> [    1.897985]  ? submit_bio_noacct+0x1e/0x260
> [    1.897989]  ext4_bio_write_page+0x222/0x420
> [    1.898000]  mpage_process_page_bufs+0x178/0x1c0
> [    1.899451]  mpage_prepare_extent_to_map+0x2d2/0x440
> [    1.899603]  ext4_writepages+0x495/0x1020
> [    1.899733]  do_writepages+0xcb/0x220
> [    1.899871]  ? __seccomp_filter+0x171/0x7e0
> [    1.900006]  file_write_and_wait_range+0xcd/0xf0
> [    1.900167]  ext4_sync_file+0x72/0x320
> [    1.900308]  __x64_sys_fsync+0x66/0xa0
> [    1.900449]  do_syscall_64+0x31/0x50
> [    1.900595]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [    1.900747] RIP: 0033:0x7ffa16ec96ea
> [    1.900883] Code: b8 4a 00 00 00 0f 05 48 3d 00 f0 ff ff 77 41 c3
> 48 83 ec 18 89 7c 24 0c e8 e3 02 f8 ff 8b 7c 24 0c 89 c2 b8 4a 00 00
> 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 43 03 f8 ff 8b
> 44 24
> [    1.901302] RSP: 002b:00007ffa143a3ac0 EFLAGS: 00000293 ORIG_RAX:
> 000000000000004a
> [    1.901499] RAX: ffffffffffffffda RBX: 0000560277ec6fe0 RCX: 00007ffa16ec96ea
> [    1.901696] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000016
> [    1.901884] RBP: 0000560277ec5910 R08: 0000000000000000 R09: 00007ffa143a4640
> [    1.902082] R10: 00007ffa16e4d39e R11: 0000000000000293 R12: 00005602773f59e0
> [    1.902459] R13: 0000000000000000 R14: 00007fffbfc007ff R15: 00007ffa13ba4000
> [    1.902763]  </TASK>
> [    1.902877] ---[ end trace 0000000000000000 ]---
> 
> To avoid calling blk_mq_start_request() twice, This patch moves the
> execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> And instead of requeuing failed request to plug list in the error path of
> virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> on the next trial.
> 
> Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> Reported-by: Alexandre Courbot <acourbot@chromium.org>
> Tested-by: Alexandre Courbot <acourbot@chromium.org>
> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> ---
> v1 -> v2
>  - Call blk_mq_start_request() after virtblk_add_req() can break the timestamp.
>    So move virtblk_add_req() before blk_mq_start_request().
>  - Use blk_mq_requeue_request() instead of requeuing failed request to plug list
>    if virtblk_add_req() fails within virtblk_add_req_batch(). 
> 
> 
>  drivers/block/virtio_blk.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Thanks for solving the timestamp issue. I'm not familiar enough which
blk_mq_requeue_request() to confirm this version is correct, but from
the virtio_blk perspective:

Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

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Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Pankaj Raghav]

On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> despite the failure.
> 
> To avoid calling blk_mq_start_request() twice, This patch moves the
> execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> And instead of requeuing failed request to plug list in the error path of
> virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> on the next trial.
> 
> Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> Reported-by: Alexandre Courbot <acourbot@chromium.org>
> Tested-by: Alexandre Courbot <acourbot@chromium.org>
> Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> ---
Looks good.
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Suwan Kim]

Hi Michael,

Can this patch be merged to the next rc?
We received two bug reports about this issue and need to fix it.

Regards,
Suwan Kim


On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
>
> On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > despite the failure.
> >
> > To avoid calling blk_mq_start_request() twice, This patch moves the
> > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > And instead of requeuing failed request to plug list in the error path of
> > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > on the next trial.
> >
> > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > ---
> Looks good.
> Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Michael S. Tsirkin]

On Thu, Sep 22, 2022 at 11:45:15PM +0900, Suwan Kim wrote:
> Hi Michael,
> 
> Can this patch be merged to the next rc?
> We received two bug reports about this issue and need to fix it.
> 
> Regards,
> Suwan Kim
> 
> 
> On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
> >
> > On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > > despite the failure.
> > >
> > > To avoid calling blk_mq_start_request() twice, This patch moves the
> > > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > > And instead of requeuing failed request to plug list in the error path of
> > > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > > on the next trial.
> > >
> > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > > ---
> > Looks good.
> > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

Stefan, Paolo, any feedback here?

-- 
MST

Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Michael S. Tsirkin]

On Thu, Sep 22, 2022 at 11:45:15PM +0900, Suwan Kim wrote:
> Hi Michael,
> 
> Can this patch be merged to the next rc?
> We received two bug reports about this issue and need to fix it.
> 
> Regards,
> Suwan Kim
> 
> 
> On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
> >
> > On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > > despite the failure.
> > >
> > > To avoid calling blk_mq_start_request() twice, This patch moves the
> > > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > > And instead of requeuing failed request to plug list in the error path of
> > > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > > on the next trial.
> > >
> > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > > ---
> > Looks good.
> > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>

Stefan, Paolo, any feedback here?

-- 
MST

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Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Michael S. Tsirkin]

On Thu, Sep 22, 2022 at 12:57:01PM -0400, Michael S. Tsirkin wrote:
> On Thu, Sep 22, 2022 at 11:45:15PM +0900, Suwan Kim wrote:
> > Hi Michael,
> > 
> > Can this patch be merged to the next rc?
> > We received two bug reports about this issue and need to fix it.
> > 
> > Regards,
> > Suwan Kim
> > 
> > 
> > On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
> > >
> > > On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > > > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > > > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > > > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > > > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > > > despite the failure.
> > > >
> > > > To avoid calling blk_mq_start_request() twice, This patch moves the
> > > > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > > > And instead of requeuing failed request to plug list in the error path of
> > > > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > > > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > > > on the next trial.
> > > >
> > > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > > > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > > > ---
> > > Looks good.
> > > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
> 
> Stefan, Paolo, any feedback here?

Oh, Stefan acked. Sorry. Will queue now.


> -- 
> MST

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization

Re: [PATCH v2] virtio-blk: Fix WARN_ON_ONCE in virtio_queue_rq()

[Michael S. Tsirkin]

On Thu, Sep 22, 2022 at 12:57:01PM -0400, Michael S. Tsirkin wrote:
> On Thu, Sep 22, 2022 at 11:45:15PM +0900, Suwan Kim wrote:
> > Hi Michael,
> > 
> > Can this patch be merged to the next rc?
> > We received two bug reports about this issue and need to fix it.
> > 
> > Regards,
> > Suwan Kim
> > 
> > 
> > On Wed, Aug 31, 2022 at 9:44 PM Pankaj Raghav <pankydev8@gmail.com> wrote:
> > >
> > > On Wed, Aug 31, 2022 at 12:01:53AM +0900, Suwan Kim wrote:
> > > > If a request fails at virtio_queue_rqs(), it is inserted to requeue_list
> > > > and passed to virtio_queue_rq(). Then blk_mq_start_request() can be called
> > > > again at virtio_queue_rq() and trigger WARN_ON_ONCE like below trace because
> > > > request state was already set to MQ_RQ_IN_FLIGHT in virtio_queue_rqs()
> > > > despite the failure.
> > > >
> > > > To avoid calling blk_mq_start_request() twice, This patch moves the
> > > > execution of blk_mq_start_request() to the end of virtblk_prep_rq().
> > > > And instead of requeuing failed request to plug list in the error path of
> > > > virtblk_add_req_batch(), it uses blk_mq_requeue_request() to change failed
> > > > request state to MQ_RQ_IDLE. Then virtblk can safely handle the request
> > > > on the next trial.
> > > >
> > > > Fixes: 0e9911fa768f ("virtio-blk: support mq_ops->queue_rqs()")
> > > > Reported-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Tested-by: Alexandre Courbot <acourbot@chromium.org>
> > > > Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
> > > > ---
> > > Looks good.
> > > Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
> 
> Stefan, Paolo, any feedback here?

Oh, Stefan acked. Sorry. Will queue now.


> -- 
> MST