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

Hi,

在 2026/2/10 1:51, Bart Van Assche 写道:

On 2/9/26 9:33 AM, Keith Busch wrote:

quoted

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/ (local)>

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/ (local)>

And the warning is added in this thread.

Bart.

-- 
Thansk,
Kuai