netdev - Re: [RFC blktests fix PATCH] tcp: use GFP_ATOMIC in tcp

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Message-ID: <c6e88bc3-8cc9-4503-a472-7692468ac218@linux.ibm.com>
Date: Tue, 25 Nov 2025 17:24:29 +0530
From: Nilay Shroff <nilay@...ux.ibm.com>
To: Christoph Hellwig <hch@....de>
Cc: Chaitanya Kulkarni <chaitanyak@...dia.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>,
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Subject: Re: [RFC blktests fix PATCH] tcp: use GFP_ATOMIC in tcp_disconnect



On 11/25/25 5:00 PM, Christoph Hellwig wrote:
> On Tue, Nov 25, 2025 at 04:58:32PM +0530, Nilay Shroff wrote:
>> >From git history, I see that was added to avoid memory reclaim  to avoid
>> possible circular locking dependency. This commit 83e1226b0ee2 ("nvme-tcp:
>> fix possible circular locking when deleting a controller under memory
>> pressure") adds it.
> 
> I suspect this was intended to be noio, and we should just switch to
> that.
> 
Yeah, I agree that this should be changed to noio. However, it seems that
this alone may not be sufficient to fix the lockdep splat reported here.
Since the real work of fput() might be deferred to another thread, using a noio
scope in this path may not have the intended effect and could end up being
redundant. 

That said, I noticed another fix from Chaitanya [1], where fput() is replaced
with __fput_sync(). With that change in place, combining the noio scope adjustment
with the switch to __fput_sync() should indeed address the lockdep issue. Given
that both problems have very similar lockdep signatures, it might make sense to
merge these two changes into a single fix.

[1] https://lore.kernel.org/all/20251125005950.41046-1-ckulkarnilinux@gmail.com/

Thanks,
--Nilay