[Qemu-block] [PATCH v2 1/6] mirror: Discard target sectors if not allocated at source side

[Fam Zheng]

If guest discards a source cluster during mirror, we would want to
discard target side as well.

Signed-off-by: Fam Zheng <address@hidden>
---
 block/mirror.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/block/mirror.c b/block/mirror.c
index 58f391a..37a5b61 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -163,6 +163,7 @@ static uint64_t coroutine_fn 
mirror_iteration(MirrorBlockJob *s)
     int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
     uint64_t delay_ns = 0;
     MirrorOp *op;
+    int pnum;
 
     s->sector_num = hbitmap_iter_next(&s->hbi);
     if (s->sector_num < 0) {
@@ -289,8 +290,15 @@ static uint64_t coroutine_fn 
mirror_iteration(MirrorBlockJob *s)
     s->in_flight++;
     s->sectors_in_flight += nb_sectors;
     trace_mirror_one_iteration(s, sector_num, nb_sectors);
-    bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
-                   mirror_read_complete, op);
+
+    if (!bdrv_is_allocated_above(source, NULL, sector_num,
+                                 nb_sectors, &pnum)) {
+        bdrv_aio_discard(s->target, sector_num, nb_sectors,
+                         mirror_write_complete, op);
+    } else {
+        bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
+                       mirror_read_complete, op);
+    }
     return delay_ns;
 }
 
-- 
1.9.3