Re: [PATCH v3 3/9] block/block-copy: specialcase first copy_range request

[Max Reitz <mreitz@redhat.com>]

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On 06.03.20 08:38, Vladimir Sementsov-Ogievskiy wrote:
> In block_copy_do_copy we fallback to read+write if copy_range failed.
> In this case copy_size is larger than defined for buffered IO, and
> there is corresponding commit. Still, backup copies data cluster by
> cluster, and most of requests are limited to one cluster anyway, so the
> only source of this one bad-limited request is copy-before-write
> operation.
> 
> Further patch will move backup to use block_copy directly, than for
> cases where copy_range is not supported, first request will be
> oversized in each backup. It's not good, let's change it now.
> 
> Fix is simple: just limit first copy_range request like buffer-based
> request. If it succeed, set larger copy_range limit.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
> ---
>  block/block-copy.c | 41 +++++++++++++++++++++++++++++++----------
>  1 file changed, 31 insertions(+), 10 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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