[PATCH 2/2] nvme: flush scan_work when resetting controller

On 6/24/2019 11:08 AM, Sagi Grimberg wrote:

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That's what I thought initially, too, but it turned out to be not
sufficient.

Not sufficient because it hangs? or panics?

It hangs, and we're seeing a warning:

kernel: [67088.344034] WARNING: CPU: 4 PID: 25020 at
../lib/percpu-refcount.c:334 percpu_ref_kill_and_confirm+0x7a/0xa0
[ .. ]
kernel: [67088.344106] Call Trace:
kernel: [67088.344112]? blk_freeze_queue_start+0x2a/0x40
kernel: [67088.344114]? blk_freeze_queue+0xe/0x40
kernel: [67088.344118]? nvme_update_disk_info+0x36/0x260 [nvme_core]
kernel: [67088.344122]? __nvme_revalidate_disk+0xca/0xf0 [nvme_core]
kernel: [67088.344125]? nvme_revalidate_disk+0xa6/0x120 [nvme_core]
kernel: [67088.344127]? ? blk_mq_get_tag+0xa3/0x220
kernel: [67088.344130]? revalidate_disk+0x23/0xc0
kernel: [67088.344133]? nvme_validate_ns+0x43/0x830 [nvme_core]
kernel: [67088.344137]? ? wake_up_q+0x70/0x70
kernel: [67088.344139]? ? blk_mq_free_request+0x12a/0x160
kernel: [67088.344142]? ? __nvme_submit_sync_cmd+0x73/0xe0 [nvme_core]
kernel: [67088.344145]? nvme_scan_work+0x2b3/0x350 [nvme_core]
kernel: [67088.344149]? process_one_work+0x1da/0x400

?From which I've inferred that we're still running a scan in parallel to
reset, and that the scan thread is calling 'blk_freeze_queue()' on a
queue which is already torn down.

Where is the scan triggered from? there is no scan call from the reset
path.

Is there a namespace removal or something else that triggers AEN
to make this happen?

What exactly is the scenario?

I believe this is from quick link bounce or logout/login testing on FC.

The loss of connectivity to the subsystem causes a reset to be done on 
the controller. Re-login causes the transport to send a discovery scan 
-or- the reconnect timer will fire, causing the controller to reconnect 
and issue the scan.

These resets and reconnects are right on the heels of each other - thus 
scan may not be finished before the reset occurs.? Reset will complete, 
as the ios it knows about are cleaned up.

-- james