Re: [PATCH v15 3/8] block: add block layer APIs resembling Linux ZonedBlockDevice ioctls

[Kevin Wolf]

Am 27.02.2023 um 20:14 hat Stefan Hajnoczi geschrieben:
> On Mon, Feb 27, 2023 at 07:20:14PM +0100, Kevin Wolf wrote:
> > Am 29.01.2023 um 11:28 hat Sam Li geschrieben:
> > > Add zoned device option to host_device BlockDriver. It will be presented 
> > > only
> > > for zoned host block devices. By adding zone management operations to the
> > > host_block_device BlockDriver, users can use the new block layer APIs
> > > including Report Zone and four zone management operations
> > > (open, close, finish, reset, reset_all).
> > > 
> > > Qemu-io uses the new APIs to perform zoned storage commands of the device:
> > > zone_report(zrp), zone_open(zo), zone_close(zc), zone_reset(zrs),
> > > zone_finish(zf).
> > > 
> > > For example, to test zone_report, use following command:
> > > $ ./build/qemu-io --image-opts -n driver=host_device, filename=/dev/nullb0
> > > -c "zrp offset nr_zones"
> > > 
> > > Signed-off-by: Sam Li <faithilikerun@gmail.com>
> > > Reviewed-by: Hannes Reinecke <hare@suse.de>
> > > Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> > > ---
> > >  block/block-backend.c             | 147 ++++++++++++++
> > >  block/file-posix.c                | 323 ++++++++++++++++++++++++++++++
> > >  block/io.c                        |  41 ++++
> > >  include/block/block-io.h          |   7 +
> > >  include/block/block_int-common.h  |  21 ++
> > >  include/block/raw-aio.h           |   6 +-
> > >  include/sysemu/block-backend-io.h |  18 ++
> > >  meson.build                       |   4 +
> > >  qemu-io-cmds.c                    | 149 ++++++++++++++
> > >  9 files changed, 715 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/block/block-backend.c b/block/block-backend.c
> > > index ba7bf1d6bc..a4847b9131 100644
> > > --- a/block/block-backend.c
> > > +++ b/block/block-backend.c
> > > @@ -1451,6 +1451,15 @@ typedef struct BlkRwCo {
> > >      void *iobuf;
> > >      int ret;
> > >      BdrvRequestFlags flags;
> > > +    union {
> > > +        struct {
> > > +            unsigned int *nr_zones;
> > > +            BlockZoneDescriptor *zones;
> > > +        } zone_report;
> > > +        struct {
> > > +            unsigned long op;
> > > +        } zone_mgmt;
> > > +    };
> > >  } BlkRwCo;
> > 
> > Should we use a different struct for blk_aio_zone_*() so that we don't
> > need to touch the one for the normal I/O path? My concern is that
> > increasing the size of the struct (currently 32 bytes) might negatively
> > impact the performance even of non-zoned devices. Maybe it turns out
> > that it wasn't really necessary in the end (have we done any
> > benchmarks?), but I don't think it can hurt anyway.
> > 
> > With this changed, you can add to the series:
> > Acked-by: Kevin Wolf <kwolf@redhat.com>
> 
> There are unused fields in BlkRwCo and BlkAioEmAIOCB, so changing the
> size of the struct isn't necessary. ioctl/flush/pdiscard already use
> BlkAioEmAIOCB/BlkRwCo for non-read/write operations, including using the
> iobuf field for different types, so it wouldn't be weird:
> 
>   typedef struct BlkRwCo {
>       BlockBackend *blk;
>       int64_t offset;
>       void *iobuf;
>             ^^^^^ used for preadv/pwritev qiov, ioctl buf, and NULL for
>                   other request types. zone_report could put the
>                   BlockZoneDescriptor pointer here. zone_mgmt could put
>                   op here.
>       int ret;
>       BdrvRequestFlags flags;
>   } BlkRwCo;
> 
>   typedef struct BlkAioEmAIOCB {
>       BlockAIOCB common;
>       BlkRwCo rwco;
>       int64_t bytes;
>               ^^^^^ zone_report could put the nr_zones pointer here
>       bool has_returned;
>   } BlkAioEmAIOCB;
> 
> Does that sound okay?

Might not be great for readability, but good enough for me.

Kevin

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