Fix -snapshot deleting images on disk change

Block device change command did not copy BDRV_O_SNAPSHOT flag. Thus
the new image did not have this flag and the file got deleted during
opening.

Fix by copying BDRV_O_SNAPSHOT flag.

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 199630b62ec7cc5efd6f860ff545b449c7b5cdb8)

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

3 files changed, 7 insertions, 0 deletions

diff --git a/block.c b/block.c
index 49e6cbcd52..452ae94eea 100644
--- a/block.c
+++ b/block.c
@@ -1811,6 +1811,11 @@ int bdrv_can_snapshot(BlockDriverState *bs)
     return 1;
 }
 
+int bdrv_is_snapshot(BlockDriverState *bs)
+{
+    return !!(bs->open_flags & BDRV_O_SNAPSHOT);
+}
+
 BlockDriverState *bdrv_snapshots(void)
 {
     BlockDriverState *bs;
diff --git a/block.h b/block.h
index c2a7e4c762..db131a3438 100644
--- a/block.h
+++ b/block.h
@@ -202,6 +202,7 @@ const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
 int bdrv_can_snapshot(BlockDriverState *bs);
+int bdrv_is_snapshot(BlockDriverState *bs);
 BlockDriverState *bdrv_snapshots(void);
 int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info);
diff --git a/blockdev.c b/blockdev.c
index 0a9dec364e..01e402bf3d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -590,6 +590,7 @@ int do_change_block(Monitor *mon, const char *device,
         return -1;
     }
     bdrv_flags = bdrv_is_read_only(bs) ? 0 : BDRV_O_RDWR;
+    bdrv_flags |= bdrv_is_snapshot(bs) ? BDRV_O_SNAPSHOT : 0;
     if (bdrv_open(bs, filename, bdrv_flags, drv) < 0) {
         qerror_report(QERR_OPEN_FILE_FAILED, filename);
         return -1;