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From: Hannes Reinecke <hare@suse.de>
To: Jens Axboe <axboe@kernel.dk>,
	linux-aio@kvack.org, linux-block@vger.kernel.org,
	linux-api@vger.kernel.org
Cc: hch@lst.de, jmoyer@redhat.com, avi@scylladb.com,
	jannh@google.com, viro@ZenIV.linux.org.uk
Subject: Re: [PATCH 19/19] io_uring: add io_uring_event cache hit information
Date: Sun, 10 Feb 2019 10:36:57 +0100
Message-ID: <ca60183a-bb43-930c-8bf1-026c2528723d@suse.de> (raw)
In-Reply-To: <20190209211346.26060-20-axboe@kernel.dk>

On 2/9/19 10:13 PM, Jens Axboe wrote:
> Add hint on whether a read was served out of the page cache, or if it
> hit media. This is useful for buffered async IO, O_DIRECT reads would
> never have this set (for obvious reasons).
> 
> If the read hit page cache, cqe->flags will have IOCQE_FLAG_CACHEHIT
> set.
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>   fs/io_uring.c                 | 7 ++++++-
>   include/uapi/linux/io_uring.h | 5 +++++
>   2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 11a549b5dcbf..d7a10484d748 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -587,11 +587,16 @@ static void io_fput(struct io_kiocb *req)
>   static void io_complete_rw(struct kiocb *kiocb, long res, long res2)
>   {
>   	struct io_kiocb *req = container_of(kiocb, struct io_kiocb, rw);
> +	unsigned ev_flags = 0;
>   
>   	kiocb_end_write(kiocb);
>   
>   	io_fput(req);
> -	io_cqring_add_event(req->ctx, req->user_data, res, 0);
> +
> +	if (res > 0 && (req->flags & REQ_F_FORCE_NONBLOCK))
> +		ev_flags = IOCQE_FLAG_CACHEHIT;
> +
> +	io_cqring_add_event(req->ctx, req->user_data, res, ev_flags);
>   	io_free_req(req);
>   }
>   
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
> index e23408692118..24906e99fdc7 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -69,6 +69,11 @@ struct io_uring_cqe {
>   	__u32	flags;
>   };
> 
> +/*
> + * io_uring_event->flags
> + */
> +#define IOCQE_FLAG_CACHEHIT	(1U << 0)	/* IO did not hit media */
> +
>   /*
>    * Magic offsets for the application to mmap the data it needs
>    */
> 

Hmm. The point of this patch being ... what?
Just setting a newly introduced flag seems to be a bit pointless.
Unless it has some magic interaction with io_cqring_add_event().
But then that function would have had to have knowledge of that flag 
already, which would be ... odd.

Please clarify.

Cheers,

Hannes

  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-09 21:13 [PATCHSET v14] io_uring IO interface Jens Axboe
2019-02-09 21:13 ` [PATCH 01/19] fs: add an iopoll method to struct file_operations Jens Axboe
2019-02-09 21:13 ` [PATCH 02/19] block: wire up block device iopoll method Jens Axboe
2019-02-09 21:13 ` [PATCH 03/19] block: add bio_set_polled() helper Jens Axboe
2019-02-09 21:13 ` [PATCH 04/19] iomap: wire up the iopoll method Jens Axboe
2019-02-09 21:13 ` [PATCH 05/19] Add io_uring IO interface Jens Axboe
2019-02-10 12:03   ` Thomas Gleixner
2019-02-10 14:19     ` Jens Axboe
2019-02-09 21:13 ` [PATCH 06/19] io_uring: add fsync support Jens Axboe
2019-02-09 21:13 ` [PATCH 07/19] io_uring: support for IO polling Jens Axboe
2019-02-09 21:13 ` [PATCH 08/19] fs: add fget_many() and fput_many() Jens Axboe
2019-02-09 21:13 ` [PATCH 09/19] io_uring: use fget/fput_many() for file references Jens Axboe
2019-02-09 21:13 ` [PATCH 10/19] io_uring: batch io_kiocb allocation Jens Axboe
2019-02-09 21:13 ` [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-02-09 21:13 ` [PATCH 12/19] io_uring: add support for pre-mapped user IO buffers Jens Axboe
2019-02-09 21:13 ` [PATCH 13/19] net: split out functions related to registering inflight socket files Jens Axboe
2019-02-09 21:13 ` [PATCH 14/19] io_uring: add file set registration Jens Axboe
2019-02-09 23:52   ` Matt Mullins
2019-02-10  0:47     ` Jens Axboe
     [not found]       ` <60e4c6a489549daad1fb2c5e8eee5496c668d79a.camel@fb.com>
2019-02-10  2:34         ` Jens Axboe
2019-02-10  2:57           ` Jens Axboe
2019-02-10 19:55             ` Matt Mullins
2019-02-09 21:13 ` [PATCH 15/19] io_uring: add submission polling Jens Axboe
2019-02-09 21:13 ` [PATCH 16/19] io_uring: add io_kiocb ref count Jens Axboe
2019-02-10  9:19   ` Hannes Reinecke
2019-02-09 21:13 ` [PATCH 17/19] io_uring: add support for IORING_OP_POLL Jens Axboe
2019-02-10  9:28   ` Hannes Reinecke
2019-02-09 21:13 ` [PATCH 18/19] io_uring: allow workqueue item to handle multiple buffered requests Jens Axboe
2019-02-10  9:31   ` Hannes Reinecke
2019-02-09 21:13 ` [PATCH 19/19] io_uring: add io_uring_event cache hit information Jens Axboe
2019-02-10  9:36   ` Hannes Reinecke [this message]
2019-02-10 13:39     ` Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2019-02-11 19:00 [PATCHSET v15] io_uring IO interface Jens Axboe
2019-02-11 19:00 ` [PATCH 19/19] io_uring: add io_uring_event cache hit information Jens Axboe
2019-02-08 17:34 [PATCHSET v13] io_uring IO interface Jens Axboe
2019-02-08 17:34 ` [PATCH 19/19] io_uring: add io_uring_event cache hit information Jens Axboe

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