sheepdog: Support BDRV_REQ_ZERO_WRITE for truncate

Our .bdrv_has_zero_init_truncate always returns 1 because sheepdog
always 0-fills; we can use that same knowledge to implement
BDRV_REQ_ZERO_WRITE by ignoring it.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200428202905.770727-6-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 2eb61938ff78335700a496eda9391fd78ea431d3..739e6dee30fa86f7f7bc9adac9aa392ebe14a85e 100644 (file)
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -1654,6 +1654,7 @@ static int sd_open(BlockDriverState *bs, QDict *options, int flags,
     memcpy(&s->inode, buf, sizeof(s->inode));
 
     bs->total_sectors = s->inode.vdi_size / BDRV_SECTOR_SIZE;
+    bs->supported_truncate_flags = BDRV_REQ_ZERO_WRITE;
     pstrcpy(s->name, sizeof(s->name), vdi);
     qemu_co_mutex_init(&s->lock);
     qemu_co_mutex_init(&s->queue_lock);