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References: <20241025213645.3464331-1-kbusch@meta.com> <20241025213645.3464331-6-kbusch@meta.com>
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From: Anuj gupta <anuj1072538@gmail.com>
Date: Tue, 29 Oct 2024 18:16:29 +0530
Message-ID: <CACzX3AvZ=+cBaoZ9oKW3osA1WiWm5H5b7+wWAouLryK4-ymYfA@mail.gmail.com>
Subject: Re: [PATCHv9 5/7] io_uring: enable per-io hinting capability
To: Keith Busch <kbusch@meta.com>
Cc: linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
linux-scsi@vger.kernel.org, io-uring@vger.kernel.org,
linux-fsdevel@vger.kernel.org, hch@lst.de, joshi.k@samsung.com,
javier.gonz@samsung.com, bvanassche@acm.org, Hannes Reinecke <hare@suse.de>,
Nitesh Shetty <nj.shetty@samsung.com>, Keith Busch <kbusch@kernel.org>
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On Sat, Oct 26, 2024 at 3:13=E2=80=AFAM Keith Busch <kbusch@meta.com> wrote=
:
>
> From: Kanchan Joshi <joshi.k@samsung.com>
>
> With F_SET_RW_HINT fcntl, user can set a hint on the file inode, and
> all the subsequent writes on the file pass that hint value down. This
> can be limiting for block device as all the writes will be tagged with
> only one lifetime hint value. Concurrent writes (with different hint
> values) are hard to manage. Per-IO hinting solves that problem.
>
> Allow userspace to pass additional metadata in the SQE.
>
> __u16 write_hint;
>
> If the hint is provided, filesystems may optionally use it. A filesytem
> may ignore this field if it does not support per-io hints, or if the
> value is invalid for its backing storage. Just like the inode hints,
> requesting values that are not supported by the hardware are not an
> error.
>
> Reviewed-by: Hannes Reinecke <hare@suse.de>
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
> include/uapi/linux/io_uring.h | 4 ++++
> io_uring/rw.c | 3 ++-
> 2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.=
h
> index 60b9c98595faf..8cdcc461d464c 100644
> --- a/include/uapi/linux/io_uring.h
> +++ b/include/uapi/linux/io_uring.h
> @@ -92,6 +92,10 @@ struct io_uring_sqe {
> __u16 addr_len;
> __u16 __pad3[1];
> };
> + struct {
> + __u16 write_hint;
> + __u16 __pad4[1];
> + };
> };
> union {
> struct {
> diff --git a/io_uring/rw.c b/io_uring/rw.c
> index 8080ffd6d5712..5a1231bfecc3a 100644
> --- a/io_uring/rw.c
> +++ b/io_uring/rw.c
> @@ -279,7 +279,8 @@ static int io_prep_rw(struct io_kiocb *req, const str=
uct io_uring_sqe *sqe,
> rw->kiocb.ki_ioprio =3D get_current_ioprio();
> }
> rw->kiocb.dio_complete =3D NULL;
> -
> + if (ddir =3D=3D ITER_SOURCE)
> + rw->kiocb.ki_write_hint =3D READ_ONCE(sqe->write_hint);
> rw->addr =3D READ_ONCE(sqe->addr);
> rw->len =3D READ_ONCE(sqe->len);
> rw->flags =3D READ_ONCE(sqe->rw_flags);
> --
> 2.43.5
>
Since this patch adds a couple of new fields, it makes sense to add
BUILD_BUG_ON() checks in io_uring_init for these fields to assert the
layout of struct io_uring_sqe. And probably a zero check for pad4 in
io_prep_rw.
--
Anuj Gupta