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>

diff --git a/block.c b/block.c
index 29869987a9fd19de80fcade03062571339cdef36..af2ab4f3ea13e1e50f414b163fe7d5cae169b645 100644 (file)
--- a/block.c
+++ b/block.c
@@ -270,6 +270,15 @@ void path_combine(char *dest, int dest_size,
     }
 }
 
+void bdrv_get_full_backing_filename(BlockDriverState *bs, char *dest, size_t sz)
+{
+    if (bs->backing_file[0] == '\0' || path_has_protocol(bs->backing_file)) {
+        pstrcpy(dest, sz, bs->backing_file);
+    } else {
+        path_combine(dest, sz, bs->filename, bs->backing_file);
+    }
+}
+
 void bdrv_register(BlockDriver *bdrv)
 {
     /* Block drivers without coroutine functions need emulation */
@@ -796,14 +805,8 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
         BlockDriver *back_drv = NULL;
 
         bs->backing_hd = bdrv_new("");
-
-        if (path_has_protocol(bs->backing_file)) {
-            pstrcpy(backing_filename, sizeof(backing_filename),
-                    bs->backing_file);
-        } else {
-            path_combine(backing_filename, sizeof(backing_filename),
-                         filename, bs->backing_file);
-        }
+        bdrv_get_full_backing_filename(bs, backing_filename,
+                                       sizeof(backing_filename));
 
         if (bs->backing_format[0] != '\0') {
             back_drv = bdrv_find_format(bs->backing_format);

diff --git a/block.h b/block.h
index f163e54b5f83b72510bbcd14e027d4f96ad29cdb..7408acc5cd305adf421b7727bd5485364ae29257 100644 (file)
--- a/block.h
+++ b/block.h
@@ -303,6 +303,8 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
+void bdrv_get_full_backing_filename(BlockDriverState *bs,
+                                    char *dest, size_t sz);
 int bdrv_can_snapshot(BlockDriverState *bs);
 int bdrv_is_snapshot(BlockDriverState *bs);
 BlockDriverState *bdrv_snapshots(void);

diff --git a/qemu-img.c b/qemu-img.c
index 0ae543cade94b5e033b21302e0b0c00e6a5d160c..5434ddc5ee22380e5da9eba9d8c1e71f3bf9d949 100644 (file)
--- 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);