qemu-img: make "info" backing file output correct and easier to use

qemu-img info should use the same logic as qemu when printing the
backing file path, or debugging becomes quite tricky.  We can also
simplify the output in case the backing file has an absolute path
or a protocol.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 7 insertions, 5 deletions

diff --git a/qemu-img.c b/qemu-img.c
index 0ae543cade..5434ddc5ee 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1138,11 +1138,13 @@ static int img_info(int argc, char **argv)
     }
     bdrv_get_backing_filename(bs, backing_filename, sizeof(backing_filename));
     if (backing_filename[0] != '\0') {
-        path_combine(backing_filename2, sizeof(backing_filename2),
-                     filename, backing_filename);
-        printf("backing file: %s (actual path: %s)\n",
-               backing_filename,
-               backing_filename2);
+        bdrv_get_full_backing_filename(bs, backing_filename2,
+                                       sizeof(backing_filename2));
+        printf("backing file: %s", backing_filename);
+        if (strcmp(backing_filename, backing_filename2) != 0) {
+            printf(" (actual path: %s)", backing_filename2);
+        }
+        putchar('\n');
     }
     dump_snapshots(bs);
     bdrv_delete(bs);