linux-kernel - Re: [PATCH 3/5] io_uring/rsrc: call io_free_node() on io_sqe_buffer

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Message-ID: <7d64216e-4bf8-4557-b8a8-7285f161a2a7@kernel.dk>
Date: Fri, 28 Feb 2025 19:23:08 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Pavel Begunkov <asml.silence@...il.com>,
 Caleb Sander Mateos <csander@...estorage.com>
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] io_uring/rsrc: call io_free_node() on
 io_sqe_buffer_register() failure

On 2/28/25 6:31 PM, Pavel Begunkov wrote:
> On 2/28/25 23:59, Caleb Sander Mateos wrote:
>> io_sqe_buffer_register() currently calls io_put_rsrc_node() if it fails
>> to fully set up the io_rsrc_node. io_put_rsrc_node() is more involved
>> than necessary, since we already know the reference count will reach 0
>> and no io_mapped_ubuf has been attached to the node yet.
>>
>> So just call io_free_node() to release the node's memory. This also
>> avoids the need to temporarily set the node's buf pointer to NULL.
>>
>> Signed-off-by: Caleb Sander Mateos <csander@...estorage.com>
>> ---
>>   io_uring/rsrc.c | 3 +--
>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
>> index 748a09cfaeaa..398c6f427bcc 100644
>> --- a/io_uring/rsrc.c
>> +++ b/io_uring/rsrc.c
>> @@ -780,11 +780,10 @@ static struct io_rsrc_node *io_sqe_buffer_register(struct io_ring_ctx *ctx,
>>           return NULL;
>>         node = io_rsrc_node_alloc(ctx, IORING_RSRC_BUFFER);
>>       if (!node)
>>           return ERR_PTR(-ENOMEM);
>> -    node->buf = NULL;
> 
> It's better to have it zeroed than set to a freed / invalid
> value, it's a slow path.

Agree, let's leave the clear, I don't like passing uninitialized memory
around.

-- 
Jens Axboe