[Qemu-devel] [PATCH 4/4] qemu-img: Fail creation if backing format is invalid

[Stefan Hajnoczi]

The qemu-img create command should check the backing format to ensure
only image files with valid backing formats are created.  By checking in
qemu-img.c we can print a useful error message.

Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 qemu-img.c |   22 ++++++++++++----------
 1 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/qemu-img.c b/qemu-img.c
index 23bb7dc..b10f363 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -300,6 +300,7 @@ static int img_create(int argc, char **argv)
     const char *base_filename = NULL;
     BlockDriver *drv, *proto_drv;
     QEMUOptionParameter *param = NULL, *create_options = NULL;
+    QEMUOptionParameter *backing_fmt = NULL;
     char *options = NULL;
 
     flags = 0;
@@ -390,14 +391,22 @@ static int img_create(int argc, char **argv)
         goto out;
     }
 
+    backing_fmt = get_option_parameter(param, BLOCK_OPT_BACKING_FMT);
+    if (backing_fmt && backing_fmt->value.s) {
+        if (!bdrv_find_format(backing_fmt->value.s)) {
+            error("Unknown backing file format '%s'",
+                  backing_fmt->value.s);
+            ret = -1;
+            goto out;
+        }
+    }
+
     // The size for the image must always be specified, with one exception:
     // If we are using a backing file, we can obtain the size from there
     if (get_option_parameter(param, BLOCK_OPT_SIZE)->value.n == -1) {
 
         QEMUOptionParameter *backing_file =
             get_option_parameter(param, BLOCK_OPT_BACKING_FILE);
-        QEMUOptionParameter *backing_fmt =
-            get_option_parameter(param, BLOCK_OPT_BACKING_FMT);
 
         if (backing_file && backing_file->value.s) {
             BlockDriverState *bs;
@@ -406,14 +415,7 @@ static int img_create(int argc, char **argv)
             char buf[32];
 
             if (backing_fmt && backing_fmt->value.s) {
-                 if (bdrv_find_format(backing_fmt->value.s)) {
-                     fmt = backing_fmt->value.s;
-                } else {
-                     error("Unknown backing file format '%s'",
-                        backing_fmt->value.s);
-                     ret = -1;
-                     goto out;
-                }
+                fmt = backing_fmt->value.s;
             }
 
             bs = bdrv_new_open(backing_file->value.s, fmt, BDRV_O_FLAGS);
-- 
1.7.2.3