Re: [Qemu-devel] [PATCH v2 5/6] raw-posix: Implement .bdrv_co_preadv/pwritev

[Eric Blake <eblake@redhat.com>]

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On 06/14/2016 07:32 AM, Kevin Wolf wrote:
> The raw-posix block driver actually supports byte-aligned requests now
> on non-O_DIRECT images, like it already (and previously incorrectly)
> claimed in bs->request_alignment.
> 
> For some block drivers this means that a RMW cycle can be avoided when
> they write sub-sector metadata e.g. for cluster allocation.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/linux-aio.c |  7 ++-----
>  block/raw-aio.h   |  3 +--
>  block/raw-posix.c | 43 +++++++++++++++++++++++--------------------
>  3 files changed, 26 insertions(+), 27 deletions(-)
> 

> -static int coroutine_fn raw_co_readv(BlockDriverState *bs, int64_t sector_num,
> -                                     int nb_sectors, QEMUIOVector *qiov)
> +static int coroutine_fn raw_co_preadv(BlockDriverState *bs, uint64_t offset,
> +                                      uint64_t bytes, QEMUIOVector *qiov,
> +                                      int flags)
>  {
> -    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_READ);
> +    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_READ);
>  }
>  
> -static int coroutine_fn raw_co_writev(BlockDriverState *bs, int64_t sector_num,
> -                                      int nb_sectors, QEMUIOVector *qiov)
> +static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, uint64_t offset,
> +                                       uint64_t bytes, QEMUIOVector *qiov,
> +                                       int flags)
>  {
> -    return raw_co_rw(bs, sector_num, nb_sectors, qiov, QEMU_AIO_WRITE);
> +    assert(flags == 0);
> +    return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);
>  }

Looks odd to assert !flags on pwritev but not on preadv.  Minor enough
that you could fix on pull request.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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