Re: [PATCH for-next 06/12] io_uring: add fixed file peeking function

[Pavel Begunkov <asml.silence@gmail.com>]

On 10/31/22 13:41, Dylan Yudaken wrote:
> Add a helper function to grab the fixed file at a given offset. Will be
> useful for retarget op handlers.
> 
> Signed-off-by: Dylan Yudaken <dylany@meta.com>
> ---
>   io_uring/io_uring.c | 26 ++++++++++++++++++++------
>   io_uring/io_uring.h |  1 +
>   2 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 32eb305c4ce7..a052653fc65e 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -1841,6 +1841,23 @@ void io_wq_submit_work(struct io_wq_work *work)
>   		io_req_task_queue_fail(req, ret);
>   }
>   
> +static unsigned long __io_file_peek_fixed(struct io_kiocb *req, int fd)
> +	__must_hold(&req->ctx->uring_lock)

Let's mark it inline, it's in the hot path. Yeah, It's small but I
battled compilers enough because from time to time they leave it
not inlined.


> +{
> +	struct io_ring_ctx *ctx = req->ctx;
> +
> +	if (unlikely((unsigned int)fd >= ctx->nr_user_files))
> +		return 0;
> +	fd = array_index_nospec(fd, ctx->nr_user_files);
> +	return io_fixed_file_slot(&ctx->file_table, fd)->file_ptr;
> +}
> +
> +struct file *io_file_peek_fixed(struct io_kiocb *req, int fd)
> +	__must_hold(&req->ctx->uring_lock)
> +{
> +	return (struct file *) (__io_file_peek_fixed(req, fd) & FFS_MASK);
> +}
> +
>   inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
>   				      unsigned int issue_flags)
>   {
> @@ -1849,17 +1866,14 @@ inline struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
>   	unsigned long file_ptr;
>   
>   	io_ring_submit_lock(ctx, issue_flags);
> -
> -	if (unlikely((unsigned int)fd >= ctx->nr_user_files))
> -		goto out;
> -	fd = array_index_nospec(fd, ctx->nr_user_files);
> -	file_ptr = io_fixed_file_slot(&ctx->file_table, fd)->file_ptr;
> +	file_ptr = __io_file_peek_fixed(req, fd);
>   	file = (struct file *) (file_ptr & FFS_MASK);
>   	file_ptr &= ~FFS_MASK;
>   	/* mask in overlapping REQ_F and FFS bits */
>   	req->flags |= (file_ptr << REQ_F_SUPPORT_NOWAIT_BIT);
>   	io_req_set_rsrc_node(req, ctx, 0);
> -out:
> +	WARN_ON_ONCE(file && !test_bit(fd, ctx->file_table.bitmap));
> +
>   	io_ring_submit_unlock(ctx, issue_flags);
>   	return file;
>   }
> diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
> index ef77d2aa3172..781471bfba12 100644
> --- a/io_uring/io_uring.h
> +++ b/io_uring/io_uring.h
> @@ -44,6 +44,7 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages);
>   struct file *io_file_get_normal(struct io_kiocb *req, int fd);
>   struct file *io_file_get_fixed(struct io_kiocb *req, int fd,
>   			       unsigned issue_flags);
> +struct file *io_file_peek_fixed(struct io_kiocb *req, int fd);
>   
>   static inline bool io_req_ffs_set(struct io_kiocb *req)
>   {

-- 
Pavel Begunkov