Re: [PATCH] io_uring: ensure REQ_F_ISREG is set async offload

[Yin Fengwei <fengwei.yin@intel.com>]

On 7/21/2022 11:11 PM, Jens Axboe wrote:
> If we're offloading requests directly to io-wq because IOSQE_ASYNC was
> set in the sqe, we can miss hashing writes appropriately because we
> haven't set REQ_F_ISREG yet. This can cause a performance regression
> with buffered writes, as io-wq then no longer correctly serializes writes
> to that file.
> 
> Ensure that we set the flags in io_prep_async_work(), which will cause
> the io-wq work item to be hashed appropriately.
> 
> Fixes: 584b0180f0f4 ("io_uring: move read/write file prep state into actual opcode handler")
> Link: https://lore.kernel.org/io-uring/20220608080054.GB22428@xsang-OptiPlex-9020/
> Reported-and-tested-by: Yin Fengwei <fengwei.yin@intel.com>
This issue is reported by (from the original report):

If you fix the issue, kindly add following tag
Reported-by: kernel test robot <oliver.sang@intel.com>



Regards
Yin, Fengwei

> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> ---
> 
> Yin, this is the 5.20 version. Once this lands upstream, I'll get the
> 5.19/18 variant sent to stable as well. Thanks!
> 
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 624535c62565..4b3fd645d023 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -406,6 +406,9 @@ static void io_prep_async_work(struct io_kiocb *req)
>  	if (req->flags & REQ_F_FORCE_ASYNC)
>  		req->work.flags |= IO_WQ_WORK_CONCURRENT;
>  
> +	if (req->file && !io_req_ffs_set(req))
> +		req->flags |= io_file_get_flags(req->file) << REQ_F_SUPPORT_NOWAIT_BIT;
> +
>  	if (req->flags & REQ_F_ISREG) {
>  		if (def->hash_reg_file || (ctx->flags & IORING_SETUP_IOPOLL))
>  			io_wq_hash_work(&req->work, file_inode(req->file));
> diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
> index 868f45d55543..5db0a60dc04e 100644
> --- a/io_uring/io_uring.h
> +++ b/io_uring/io_uring.h
> @@ -41,6 +41,11 @@ 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);
>  
> +static inline bool io_req_ffs_set(struct io_kiocb *req)
> +{
> +	return req->flags & REQ_F_FIXED_FILE;
> +}
> +
>  bool io_is_uring_fops(struct file *file);
>  bool io_alloc_async_data(struct io_kiocb *req);
>  void io_req_task_work_add(struct io_kiocb *req);
> diff --git a/io_uring/rw.c b/io_uring/rw.c
> index ade3e235f277..c50a0d66d67a 100644
> --- a/io_uring/rw.c
> +++ b/io_uring/rw.c
> @@ -647,11 +647,6 @@ static bool need_read_all(struct io_kiocb *req)
>  		S_ISBLK(file_inode(req->file)->i_mode);
>  }
>  
> -static inline bool io_req_ffs_set(struct io_kiocb *req)
> -{
> -	return req->flags & REQ_F_FIXED_FILE;
> -}
> -
>  static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
>  {
>  	struct io_rw *rw = io_kiocb_to_cmd(req);
>