[Libguestfs] [Qemu-devel] [PATCH 2/5] nbd: Prepare for NBD_CMD_FLAG_FAST_ZERO

[Vladimir Sementsov-Ogievskiy]

23.08.2019 17:37, Eric Blake wrote:
> Commit fe0480d6 and friends added BDRV_REQ_NO_FALLBACK as a way to
> avoid wasting time on a preliminary write-zero request that will later
> be rewritten by actual data, if it is known that the write-zero
> request will use a slow fallback; but in doing so, could not optimize
> for NBD.  The NBD specification is now considering an extension that
> will allow passing on those semantics; this patch updates the new
> protocol bits and 'qemu-nbd --list' output to recognize the bit, as
> well as the new errno value possible when using the new flag; while
> upcoming patches will improve the client to use the feature when
> present, and the server to advertise support for it.
> 
> Signed-off-by: Eric Blake<eblake at redhat.com>

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov at virtuozzo.com>

-- 
Best regards,
Vladimir