[PATCH 4/4] blk-mq: use blk_queue_enter/exit to protect debugfs file creation

[Yu Kuai]

Hi,

在 2026/2/10 1:51, Bart Van Assche 写道:
> On 2/9/26 9:33 AM, Keith Busch wrote:
>> I had to look up the original commit that introduced the WARN,
>> 65d466b629847. The commit message says "Creating new debugfs entries can
>> trigger fs reclaim", so that must be the path that enters back into the
>> block layer request_queue.
>
> Thanks Keith. It's probably a good idea to integrate this information in
> the source code comment above the blk_queue_enter() call.

Yeah, I'll add the information in the next version.

BTW, I'd like to add something. The original lockdep report is:

[REPORT] Possible circular locking dependency on 6.18-rc2 in 
blkg_conf_open_bdev_frozen+0x80/0xa0 - David Wei <https://lore.kernel.org/all/63c97224-0e9a-4dd8-8706-38c10a1506e9@davidwei.uk/>

And we see there some contexts like wbt/nbd can freeze queue fist and then create debugfs
entries, and it's fixed by the thread:

[PATCH v9 0/8] blk-mq: fix possible deadlocks - Yu Kuai <https://lore.kernel.org/all/20260202080523.3947504-1-yukuai@fnnas.com/>

And the warning is added in this thread.

>
> Bart.

-- 
Thansk,
Kuai