From: Fam Zheng <f...@redhat.com>
Opening the backing image for the second time is bad, especially here
when it is also in use as the active image as the source. The
drive-backup job itself doesn't read from target->backing for COW,
instead it gets data from the write notifier, so it's not a big problem.
However, exporting the target to NBD etc. won't work, because of the
likely stale metadata cache.
Use BDRV_O_NO_BACKING in this case and manually set up the backing
BdrvChild.
Cc: qemu-sta...@nongnu.org
Signed-off-by: Fam Zheng <f...@redhat.com>
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
blockdev.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/blockdev.c b/blockdev.c
index 0b38c3d..0d3773b 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3151,6 +3151,7 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
BlockJobTxn *txn,
Error *local_err = NULL;
int flags;
int64_t size;
+ bool set_backing_hd = false;
if (!backup->has_speed) {
backup->speed = 0;
@@ -3201,6 +3202,8 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
BlockJobTxn *txn,
}
if (backup->sync == MIRROR_SYNC_MODE_NONE) {
source = bs;
+ flags |= BDRV_O_NO_BACKING;
+ set_backing_hd = true;
}
size = bdrv_getlength(bs);
@@ -3227,7 +3230,9 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
BlockJobTxn *txn,
}
if (backup->format) {
- options = qdict_new();
+ if (!options) {
+ options = qdict_new();
+ }
qdict_put_str(options, "driver", backup->format);
}
@@ -3238,6 +3243,14 @@ static BlockJob *do_drive_backup(DriveBackup *backup,
BlockJobTxn *txn,
bdrv_set_aio_context(target_bs, aio_context);
+ if (set_backing_hd) {
+ bdrv_set_backing_hd(target_bs, source, &local_err);
+ if (local_err) {
+ bdrv_unref(target_bs);
+ goto out;
+ }
+ }
+
if (backup->has_bitmap) {
bmap = bdrv_find_dirty_bitmap(bs, backup->bitmap);
if (!bmap) {
--
1.8.3.1
