Re: [Qemu-devel] [PATCH 0/4] block: Trivial fixes in offloading code

[Fam Zheng <famz@redhat.com>]

On Mon, 07/02 14:35, Max Reitz wrote:
> On 2018-07-02 04:58, Fam Zheng wrote:
> > These are the low priority ones spotted by Kevin and Max last week.
> > 
> > Fam Zheng (4):
> >   qcow2: Drop unused cluster_data
> >   file-posix: Fix fd_open check in raw_co_copy_range_to
> >   qcow2: Drop unreachable break
> >   raw: Drop superfluous semicolon
> > 
> >  block/file-posix.c | 2 +-
> >  block/qcow2.c      | 3 ---
> >  block/raw-format.c | 2 +-
> >  3 files changed, 2 insertions(+), 5 deletions(-)
> 
> Thanks, applied to my block branch:
> 
> https://git.xanclic.moe/XanClic/qemu/commits/branch/block
> 
> 
> Do you want to make qcow2_co_copy_range_to() do something special on
> BDRV_REQ_ZERO_WRITE?  To me, it seems natural, but on the other hand
> maybe it wouldn't bring anything.  If the protocol layer supports copy
> offloading, then it'll probably do that zero write efficiently anyway.
> If it doesn't, qemu-img convert will just fall back to the usual
> implementation which involves writing zeroes when zeroes are read, so...
>  What's your opinion?

In bdrv_co_copy_range_internal() there is

    if (flags & BDRV_REQ_ZERO_WRITE) {
        return bdrv_co_pwrite_zeroes(dst, dst_offset, bytes, flags);
    }

before calling driver .bdrv_co_copy_range_to() callback. I think this is enough?

Fam