From c7c2769c0e5769eaad9d968fe2161505b657e02a Mon Sep 17 00:00:00 2001
From: "Denis V. Lunev" <den@openvz.org>
Date: Thu, 14 Jul 2016 16:33:28 +0300
Subject: [PATCH] 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>
---
block/mirror.c | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)
diff --git a/block/mirror.c b/block/mirror.c
index b7b1ded30f..0262b03989 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -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. */