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mirror: efficiently zero out target 

With a bdrv_co_write_zeroes method on a target BDS and when this method
is working as indicated by the bdrv_can_write_zeroes_with_unmap(), zeroes
will not be placed into the wire. Thus the target could be very efficiently
zeroed out. This should be done with the largest chunk possible.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy<vsementsov@virtuozzo.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 1468503209-19498-8-git-send-email-den@openvz.org
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Jeff Cody <jcody@redhat.com>
CC: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
This commit is contained in:
Denis V. Lunev 2016-07-14 16:33:28 +03:00 committed by Jeff Cody
parent b7d5062c9c
commit c7c2769c0e
1 changed files with 26 additions and 2 deletions
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28
block/mirror.c
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@ -538,8 +538,32 @@ static int coroutine_fn mirror_dirty_init(MirrorBlockJob *s)
end = s->bdev_length / BDRV_SECTOR_SIZE;
if (base == NULL && !bdrv_has_zero_init(target_bs)) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, 0, end);
return 0;
if (!bdrv_can_write_zeroes_with_unmap(target_bs)) {
bdrv_set_dirty_bitmap(s->dirty_bitmap, 0, end);
return 0;
}
for (sector_num = 0; sector_num < end; ) {
int nb_sectors = MIN(end - sector_num,
QEMU_ALIGN_DOWN(INT_MAX, s->granularity) >> BDRV_SECTOR_BITS);
mirror_throttle(s);
if (block_job_is_cancelled(&s->common)) {
return 0;
}
if (s->in_flight >= MAX_IN_FLIGHT) {
trace_mirror_yield(s, s->in_flight, s->buf_free_count, -1);
mirror_wait_for_io(s);
continue;
}
mirror_do_zero_or_discard(s, sector_num, nb_sectors, false);
sector_num += nb_sectors;
}
mirror_drain(s);
}
/* First part, loop on the sectors and initialize the dirty bitmap. */