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 <[email protected]> Reviewed-by: Vladimir Sementsov-Ogievskiy<[email protected]> Reviewed-by: Fam Zheng <[email protected]> CC: Stefan Hajnoczi <[email protected]> CC: Kevin Wolf <[email protected]> CC: Max Reitz <[email protected]> CC: Jeff Cody <[email protected]> CC: Eric Blake <[email protected]> --- block/mirror.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/block/mirror.c b/block/mirror.c index d0fa457..ae70c3b 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -536,8 +536,32 @@ 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. */ -- 2.5.0
