Re: [PATCH net 1/1] net/rds: handle zerocopy send cleanup before the message is queued

[Paolo Abeni <pabeni@redhat.com>]

On 5/1/26 9:40 PM, Allison Henderson wrote:
> On Fri, 2026-05-01 at 09:08 +0800, Ren Wei wrote:
>> From: Nan Li <tonanli66@gmail.com>
>>
>> A zerocopy send can fail after user pages have been pinned but before
>> the message is attached to the sending socket.
>>
>> The purge path currently infers zerocopy state from rm->m_rs, so an
>> unqueued message can be cleaned up as if it owned normal payload pages.
>> However, zerocopy ownership is really determined by the presence of
>> op_mmp_znotifier, regardless of whether the message has reached the
>> socket queue.
>>
>> Capture op_mmp_znotifier up front in rds_message_purge() and use it as
>> the cleanup discriminator. If the message is already associated with a
>> socket, keep the existing completion path. Otherwise, drop the pinned
>> page accounting directly and release the notifier before putting the
>> payload pages.
>>
>> This keeps early send failure cleanup consistent with the zerocopy
>> lifetime rules without changing the normal queued completion path.
>>
>> Fixes: 0cebaccef3ac ("rds: zerocopy Tx support.")
>> Cc: stable@kernel.org
>> Reported-by: Yuan Tan <yuantan098@gmail.com>
>> Reported-by: Yifan Wu <yifanwucs@gmail.com>
>> Reported-by: Juefei Pu <tomapufckgml@gmail.com>
>> Reported-by: Xin Liu <bird@lzu.edu.cn>
>> Co-developed-by: Xiao Liu <lx24@stu.ynu.edu.cn>
>> Signed-off-by: Xiao Liu <lx24@stu.ynu.edu.cn>
>> Signed-off-by: Nan Li <tonanli66@gmail.com>
>> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
> 
> This fix looks fine to me.  Thanks Ren Wei!
> Reviewed-by: Allison Henderson <achender@kernel.org>

Note that sashiko spotted more pre-existing problems in this area,
please have a look:

https://sashiko.dev/#/patchset/d2ea98a6313d5467bac00f7c9fef8c7acddb9258.1777550074.git.tonanli66%40gmail.com

/P