linux-kernel - Re: [PATCH v2] io_uring/rsrc: Simplify buffer cloning by locking both rings

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Message-ID: <a652b0a2-4ff6-487e-bc0e-2e3840a2abea@kernel.dk>
Date: Wed, 15 Jan 2025 13:31:11 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Jann Horn <jannh@...gle.com>, Pavel Begunkov <asml.silence@...il.com>
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] io_uring/rsrc: Simplify buffer cloning by locking both
 rings

On 1/15/25 1:26 PM, Jann Horn wrote:
> The locking in the buffer cloning code is somewhat complex because it goes
> back and forth between locking the source ring and the destination ring.
> 
> Make it easier to reason about by locking both rings at the same time.
> To avoid ABBA deadlocks, lock the rings in ascending kernel address order,
> just like in lock_two_nondirectories().

I'm going to let this one sit for review for a day or two, and since it
depends changes slated for 6.13, I'll queue it up in a post-merge branch
for 6.14 if all goes well.

Thanks!

-- 
Jens Axboe