[Qemu-devel] [PATCH v4 22/25] block: Do not copy exact_filename from format file

[Max Reitz <mreitz@redhat.com>]

If the a format BDS's file BDS is in turn a format BDS, we cannot simply
use the same filename, because when opening a BDS tree based on a
filename alone, qemu will create only one format node on top of one
protocol node (disregarding a potential backing file).

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 block.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/block.c b/block.c
index be811457ed..3a2085b631 100644
--- a/block.c
+++ b/block.c
@@ -4095,9 +4095,20 @@ void bdrv_refresh_filename(BlockDriverState *bs)
 
         bs->exact_filename[0] = '\0';
 
-        /* If no specific options have been given for this BDS, the filename of
-         * the underlying file should suffice for this one as well */
-        if (bs->file->bs->exact_filename[0] && !generate_json_filename) {
+        /* We can use the underlying file's filename if:
+         * - it has a filename,
+         * - the file is a protocol BDS, and
+         * - opening that file (as this BDS's format) will automatically create
+         *   the BDS tree we have right now, that is:
+         *   - the user did not significantly change this BDS's behavior with
+         *     some explicit options
+         *   - no non-file child of this BDS has been overridden by the user
+         *   Both of these conditions are represented by generate_json_filename.
+         */
+        if (bs->file->bs->exact_filename[0] &&
+            bs->file->bs->drv->bdrv_file_open &&
+            !generate_json_filename)
+        {
             strcpy(bs->exact_filename, bs->file->bs->exact_filename);
         }
     }
-- 
2.11.0