netdev - Re: [PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx queue

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Message-ID: <5eac0173-c75e-40b3-a1bd-7cedf86237df@davidwei.uk>
Date: Tue, 18 Feb 2025 14:06:50 -0800
From: David Wei <dw@...idwei.uk>
To: Kees Bakker <kees@...erbout.nl>, io-uring@...r.kernel.org,
 netdev@...r.kernel.org
Cc: Jens Axboe <axboe@...nel.dk>, Pavel Begunkov <asml.silence@...il.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jesper Dangaard Brouer <hawk@...nel.org>, David Ahern <dsahern@...nel.org>,
 Mina Almasry <almasrymina@...gle.com>,
 Stanislav Fomichev <stfomichev@...il.com>, Joe Damato <jdamato@...tly.com>,
 Pedro Tammela <pctammela@...atatu.com>, lizetao <lizetao1@...wei.com>
Subject: Re: [PATCH v14 07/11] io_uring/zcrx: set pp memory provider for an rx
 queue

On 2025-02-18 11:40, Kees Bakker wrote:
> Op 15-02-2025 om 01:09 schreef David Wei:
>> Set the page pool memory provider for the rx queue configured for zero
>> copy to io_uring. Then the rx queue is reset using
>> netdev_rx_queue_restart() and netdev core + page pool will take care of
>> filling the rx queue from the io_uring zero copy memory provider.
>>
>> For now, there is only one ifq so its destruction happens implicitly
>> during io_uring cleanup.
>>
>> Reviewed-by: Jens Axboe <axboe@...nel.dk>
>> Signed-off-by: David Wei <dw@...idwei.uk>
>> ---
>>   io_uring/zcrx.c | 49 +++++++++++++++++++++++++++++++++++++++++--------
>>   1 file changed, 41 insertions(+), 8 deletions(-)
>>
>> diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
>> index 8833879d94ba..7d24fc98b306 100644
>> --- a/io_uring/zcrx.c
>> +++ b/io_uring/zcrx.c
>> [...]
>> @@ -444,6 +475,8 @@ void io_shutdown_zcrx_ifqs(struct io_ring_ctx *ctx)
>>         if (ctx->ifq)
>>           io_zcrx_scrub(ctx->ifq);
>> +
>> +    io_close_queue(ctx->ifq);
> If ctx->ifq is NULL (which seems to be not unlikely given the if statement above)
> then you'll get a NULL pointer dereference in io_close_queue().

The only caller of io_shutdown_zcrx_ifqs() is io_ring_exit_work() which
checks for ctx->ifq first. That does mean the ctx->ifq check is
redundant in this function though.

>>   }
>>     static inline u32 io_zcrx_rqring_entries(struct io_zcrx_ifq *ifq)
>