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

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Message-ID: <f74d6e16-29fb-4a9a-a6aa-9a7170c683ba@gmail.com>
Date: Sat, 1 Mar 2025 01:31:01 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Caleb Sander Mateos <csander@...estorage.com>,
 Jens Axboe <axboe@...nel.dk>
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 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.

-- 
Pavel Begunkov