On 2021/10/05 10:31, Ming Lei wrote:
On Thu, Sep 30, 2021 at 08:56:29AM -0700, Bart Van Assche wrote:
On 9/30/21 5:56 AM, Ming Lei wrote:
Turns out that blk_mq_freeze_queue() isn't stronger[1] than
blk_mq_quiesce_queue() because dispatch may still be in-progress after
queue is frozen, and in several cases, such as switching io scheduler,
updating nr_requests & wbt latency, we still need to quiesce queue as a
supplement of freezing queue.
Is there agreement about this? If not, how about leaving out the above from the
patch description?
Yeah, actually the code has been merged, please see the related
functions: elevator_switch(), queue_wb_lat_store() and
blk_mq_update_nr_requests().
As we need to extend uses of blk_mq_quiesce_queue(), it is inevitable
for us to need support nested quiesce, especially we can't let
unquiesce happen when there is quiesce originated from other contexts.
This patch introduces q->mq_quiesce_depth to deal concurrent quiesce,
and we only unquiesce queue when it is the last/outer-most one of all
contexts.
One kernel panic issue has been reported[2] when running stress test on
dm-mpath's updating nr_requests and suspending queue, and the similar
issue should exist on almost all drivers which use quiesce/unquiesce.
[1] https://marc.info/?l=linux-block&m=150993988115872&w=2
[2] https://listman.redhat.com/archives/dm-devel/2021-September/msg00189.html
Please share the call stack of the kernel oops fixed by [2] since that
call stack is not in the patch description.
OK, it is something like the following:
[ 145.453672] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-2.fc30 04/01/2014
[ 145.454104] RIP: 0010:dm_softirq_done+0x46/0x220 [dm_mod]
[ 145.454536] Code: 85 ed 0f 84 40 01 00 00 44 0f b6 b7 70 01 00 00 4c 8b a5 18 01 00 00 45 89 f5 f6 47 1d 04 75 57 49 8b 7c 24 08 48 85 ff 74 4d <48> 8b 47 08 48 8b 40 58 48 85 c0 74 40 49 8d 4c 24 50 44 89 f2 48
[ 145.455423] RSP: 0000:ffffa88600003ef8 EFLAGS: 00010282
[ 145.455865] RAX: ffffffffc03fbd10 RBX: ffff979144c00010 RCX: dead000000000200
[ 145.456321] RDX: ffffa88600003f30 RSI: ffff979144c00068 RDI: ffffa88600d01040
[ 145.456764] RBP: ffff979150eb7990 R08: ffff9791bbc27de0 R09: 0000000000000100
[ 145.457205] R10: 0000000000000068 R11: 000000000000004c R12: ffff979144c00138
[ 145.457647] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000010
[ 145.458080] FS: 00007f57e5d13180(0000) GS:ffff9791bbc00000(0000) knlGS:0000000000000000
[ 145.458516] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 145.458945] CR2: ffffa88600d01048 CR3: 0000000106cf8003 CR4: 0000000000370ef0
[ 145.459382] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 145.459815] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 145.460250] Call Trace:
[ 145.460779] <IRQ>
[ 145.461453] blk_done_softirq+0xa1/0xd0
[ 145.462138] __do_softirq+0xd7/0x2d6
[ 145.462814] irq_exit+0xf7/0x100
[ 145.463480] do_IRQ+0x7f/0xd0
[ 145.464131] common_interrupt+0xf/0xf
[ 145.464797] </IRQ>
Hi, out test can repoduce this problem:
[ 139.158093] BUG: kernel NULL pointer dereference, address:
0000000000000008
[ 139.160285] #PF: supervisor read access in kernel mode
[ 139.161905] #PF: error_code(0x0000) - not-present page
[ 139.163513] PGD 172745067 P4D 172745067 PUD 17fa88067 PMD 0
[ 139.164506] Oops: 0000 [#1] PREEMPT SMP
[ 139.165034] CPU: 17 PID: 1083 Comm: nbd-client Not tainted
5.15.0-rc4-next-20211007-dirty #94
[ 139.166179] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS ?-20190727_073836-buildvm-p4
[ 139.167962] RIP: 0010:kyber_has_work+0x31/0xb0
[ 139.168571] Code: 41 bd 48 00 00 00 41 54 45 31 e4 55 53 48 8b 9f b0
00 00 00 48 8d 6b 08 49 63 c4 d
[ 139.171039] RSP: 0018:ffffc90000f479c8 EFLAGS: 00010246
[ 139.171740] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
ffff888176218f40
[ 139.172680] RDX: ffffffffffffffff RSI: ffffc90000f479f4 RDI:
ffff888175310000
[ 139.173611] RBP: 0000000000000008 R08: 0000000000000000 R09:
ffff88882fa6c0a8
[ 139.174541] R10: 000000000000030e R11: ffff88817fbcfa10 R12:
0000000000000000
[ 139.175482] R13: 0000000000000048 R14: ffffffff99b7e340 R15:
ffff8881783edc00
[ 139.176402] FS: 00007fa8e62e4b40(0000) GS:ffff88882fa40000(0000)
knlGS:0000000000000000
[ 139.177434] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 139.178190] CR2: 0000000000000008 CR3: 00000001796ac000 CR4:
00000000000006e0
[ 139.179127] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 139.180066] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[ 139.181000] Call Trace:
[ 139.182338] <TASK>
[ 139.182638] blk_mq_run_hw_queue+0x135/0x180
[ 139.183207] blk_mq_run_hw_queues+0x80/0x150
[ 139.183766] blk_mq_unquiesce_queue+0x33/0x40
[ 139.184329] nbd_clear_que+0x52/0xb0 [nbd]
[ 139.184869] nbd_disconnect_and_put+0x6b/0xe0 [nbd]
[ 139.185499] nbd_genl_disconnect+0x125/0x290 [nbd]
[ 139.186123] genl_family_rcv_msg_doit.isra.0+0x102/0x1b0
[ 139.186821] genl_rcv_msg+0xfc/0x2b0
[ 139.187300] ? nbd_ioctl+0x500/0x500 [nbd]
[ 139.187847] ? genl_family_rcv_msg_doit.isra.0+0x1b0/0x1b0
[ 139.188564] netlink_rcv_skb+0x62/0x180
[ 139.189075] genl_rcv+0x34/0x60
[ 139.189490] netlink_unicast+0x26d/0x590
[ 139.190006] netlink_sendmsg+0x3a1/0x6d0
[ 139.190513] ? netlink_rcv_skb+0x180/0x180
[ 139.191039] ____sys_sendmsg+0x1da/0x320
[ 139.191556] ? ____sys_recvmsg+0x130/0x220
[ 139.192095] ___sys_sendmsg+0x8e/0xf0
[ 139.192591] ? ___sys_recvmsg+0xa2/0xf0
[ 139.193102] ? __wake_up_common_lock+0xac/0xe0
[ 139.193699] __sys_sendmsg+0x6d/0xe0
[ 139.194167] __x64_sys_sendmsg+0x23/0x30
[ 139.194675] do_syscall_64+0x35/0x80
[ 139.195145] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 139.195806] RIP: 0033:0x7fa8e59ebb87
[ 139.196281] Code: 64 89 02 48 c7 c0 ff ff ff ff eb b9 0f 1f 80 00 00
00 00 8b 05 6a 2b 2c 00 48 63 8
[ 139.198715] RSP: 002b:00007ffd50573c38 EFLAGS: 00000246 ORIG_RAX:
000000000000002e
[ 139.199710] RAX: ffffffffffffffda RBX: 0000000001318120 RCX:
00007fa8e59ebb87
[ 139.200643] RDX: 0000000000000000 RSI: 00007ffd50573c70 RDI:
0000000000000003
[ 139.201583] RBP: 00000000013181f0 R08: 0000000000000014 R09:
0000000000000002
[ 139.202512] R10: 0000000000000006 R11: 0000000000000246 R12:
0000000001318030
[ 139.203434] R13: 00007ffd50573c70 R14: 0000000000000001 R15:
00000000ffffffff
[ 139.204364] </TASK>
[ 139.204652] Modules linked in: nbd
[ 139.205101] CR2: 0000000000000008
[ 139.205580] ---[ end trace 0248c57101a02431 ]---
hope the call stack can be helpful.
Thanks,
Kuai
