[Qemu-devel] [PATCH v3 11/12] block/qapi: Ignore filters on top for format name

[Max Reitz]

bdrv_query_image_info() currently deduces the image filename and the
format name from the top BDS. However, it is probably more reasonable to
ignore as many filters as possible on top of the BDS chain since those
neither change the type nor the filename of the underlying image.

Filters like quorum which have multiple underlying BDS should not be
removed, however, since the underlying BDS chains may lead to different
image formats and most certainly to different filenames. Therefore, only
simple filters with a single underlying BDS may be skipped.

In addition, any "raw" BDS on top of such a simple filter should be
removed, since they have probably been automatically created by
bdrv_open() but basically function as a simple filter as well.

Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Benoit Canet <address@hidden>
---
 block/qapi.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/block/qapi.c b/block/qapi.c
index 8f2b4db..84b3097 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -171,11 +171,25 @@ void bdrv_query_image_info(BlockDriverState *bs,
     int ret;
     Error *err = NULL;
     ImageInfo *info = g_new0(ImageInfo, 1);
+    BlockDriverState *ubs;
 
     bdrv_get_geometry(bs, &total_sectors);
 
-    info->filename        = g_strdup(bs->filename);
-    info->format          = g_strdup(bdrv_get_format_name(bs));
+    /* Remove the top layer of filters; that is, remove every "raw" BDS on top
+     * of a single-child filter and every single-child filter itself until a 
BDS
+     * is encountered which cannot be removed through these rules */
+    ubs = bs;
+    while ((ubs->drv && ubs->drv->is_filter && ubs->drv->has_single_child) ||
+           (ubs->drv && !strcmp(ubs->drv->format_name, "raw") && ubs->file &&
+            ubs->file->drv && ubs->file->drv->is_filter &&
+            ubs->file->drv->has_single_child))
+    {
+        ubs = ubs->file;
+    }
+
+    info->filename        = g_strdup(ubs->filename);
+    info->format          = g_strdup(bdrv_get_format_name(ubs));
+
     info->virtual_size    = total_sectors * 512;
     info->actual_size     = bdrv_get_allocated_file_size(bs);
     info->has_actual_size = info->actual_size >= 0;
-- 
1.9.1