RE: [PATCH v2] io_uring/futex: Factor out common free logic into io_free_ifd()

[lizetao <lizetao1@huawei.com>]

Hi,

> -----Original Message-----
> From: Sidong Yang <sidong.yang@furiosa.ai>
> Sent: Friday, January 24, 2025 11:44 PM
> To: io-uring <io-uring@vger.kernel.org>; Jens Axboe <axboe@kernel.dk>
> Cc: Sidong Yang <sidong.yang@furiosa.ai>
> Subject: [PATCH v2] io_uring/futex: Factor out common free logic into
> io_free_ifd()
> 
> This patch introduces io_free_ifd() that try to cache or free io_futex_data. It
> could be used for completion. It also could be used for error path in
> io_futex_wait(). Old code just release the ifd but it could be cached.
> 
> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
> v2: use io_free_ifd() for completion
> ---
>  io_uring/futex.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/io_uring/futex.c b/io_uring/futex.c index
> e29662f039e1..94a7159f9cff 100644
> --- a/io_uring/futex.c
> +++ b/io_uring/futex.c
> @@ -44,6 +44,13 @@ void io_futex_cache_free(struct io_ring_ctx *ctx)
>  	io_alloc_cache_free(&ctx->futex_cache, kfree);  }
> 
> +static void io_free_ifd(struct io_ring_ctx *ctx, struct io_futex_data
> +*ifd) {
> +	if (!io_alloc_cache_put(&ctx->futex_cache, ifd)) {
> +		kfree(ifd);
> +	}
> +}

inline static void io_free_ifd(struct io_ring_ctx *ctx, struct io_futex_data *ifd)
{
	if (!io_alloc_cache_put(&ctx->futex_cache, ifd))
		kfree(ifd);
}

Maybe inline function would be better here, and the code format needs to be fine-tuned.

> +
>  static void __io_futex_complete(struct io_kiocb *req, struct io_tw_state *ts)  {
>  	req->async_data = NULL;
> @@ -57,8 +64,7 @@ static void io_futex_complete(struct io_kiocb *req, struct
> io_tw_state *ts)
>  	struct io_ring_ctx *ctx = req->ctx;
> 
>  	io_tw_lock(ctx, ts);
> -	if (!io_alloc_cache_put(&ctx->futex_cache, ifd))
> -		kfree(ifd);
> +	io_free_ifd(ctx, ifd);
>  	__io_futex_complete(req, ts);
>  }
> 
> @@ -353,13 +359,13 @@ int io_futex_wait(struct io_kiocb *req, unsigned int
> issue_flags)
>  		return IOU_ISSUE_SKIP_COMPLETE;
>  	}
> 
> +	io_free_ifd(ctx, ifd);
>  done_unlock:
>  	io_ring_submit_unlock(ctx, issue_flags);
>  done:
>  	if (ret < 0)
>  		req_set_fail(req);
>  	io_req_set_res(req, ret, 0);
> -	kfree(ifd);

Since kfree() is deleted, it is redundant to initialize ifd to NULL. You can consider modifying it like this:
-       struct io_futex_data *ifd = NULL;
        struct futex_hash_bucket *hb;
+       struct io_futex_data *ifd;

>  	return IOU_OK;
>  }
> 
> --
> 2.43.0
> 

--
Li Zetao