Re: [PATCH 3/3] io_uring: add support for zone-append

[javier.gonz@xxxxxxxxxxx]

On 18.06.2020 07:39, Damien Le Moal wrote:
> On 2020/06/18 2:27, Kanchan Joshi wrote:
> > From: Selvakumar S <selvakuma.s1@xxxxxxxxxxx>
> >
> > Introduce three new opcodes for zone-append -
> >
> >    IORING_OP_ZONE_APPEND     : non-vectord, similiar to IORING_OP_WRITE
> >    IORING_OP_ZONE_APPENDV    : vectored, similar to IORING_OP_WRITEV
> >    IORING_OP_ZONE_APPEND_FIXED : append using fixed-buffers
> >
> > Repurpose cqe->flags to return zone-relative offset.
> >
> > Signed-off-by: SelvaKumar S <selvakuma.s1@xxxxxxxxxxx>
> > Signed-off-by: Kanchan Joshi <joshi.k@xxxxxxxxxxx>
> > Signed-off-by: Nitesh Shetty <nj.shetty@xxxxxxxxxxx>
> > Signed-off-by: Javier Gonzalez <javier.gonz@xxxxxxxxxxx>
> > ---
> >  fs/io_uring.c                 | 72 +++++++++++++++++++++++++++++++++++++++++--
> >  include/uapi/linux/io_uring.h |  8 ++++-
> >  2 files changed, 77 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/io_uring.c b/fs/io_uring.c
> > index 155f3d8..c14c873 100644
> > --- a/fs/io_uring.c
> > +++ b/fs/io_uring.c
> > @@ -649,6 +649,10 @@ struct io_kiocb {
> >  	unsigned long		fsize;
> >  	u64			user_data;
> >  	u32			result;
> > +#ifdef CONFIG_BLK_DEV_ZONED
> > +	/* zone-relative offset for append, in bytes */
> > +	u32			append_offset;
>
> this can overflow. u64 is needed.

We chose to do it this way to start with because struct io_uring_cqe
only has space for u32 when we reuse the flags.

We can of course create a new cqe structure, but that will come with
larger changes to io_uring for supporting append.

Do you believe this is a better approach?

Javier