We should split requests even if they are less than write_zeroes_alignment.
For example we can have the following request:
offset 62k
size 4k
write_zeroes_alignment 64k
The original code sent 1 request covering 2 qcow2 clusters, and resulted
in both clusters being allocated. But by splitting the request, we can
cater to the case where one of the two clusters can be zeroed as a
whole, for only 1 cluster allocated after the operation.
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Eric Blake <eblake@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Message-Id: <1463476543-3087-2-git-send-email-den@openvz.org>
[eblake: Avoid exceeding nb_sectors, hoist alignment checks out of
loop, and update testsuite to show that patch works]
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This covers some more write_zeroes cases which are relevant for the
recent qcow2 optimisations that check the allocation status of the
backing file for partial cluster write_zeroes requests.
This needs to be separate from 034 because we can only support qcow2 in
this test case for multiple reasons: We check the allocation status
after write_zeroes with 'qemu-img map' and the optimised behaviour that
produces zero clusters is only implemented in qcow2; second, the map
command returns offsets that are qcow2 specific; and finally, we also
use 512 byte clusters which aren't supported for formats like qed.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Denis V. Lunev