block: support known backing format for image create and open (Uri Lublin)

Added a backing_format field to BlockDriverState.
Added bdrv_create2 and drv->bdrv_create2 to create an image with
a known backing file format.
Upon bdrv_open2 if backing format is known use it, instead of
probing the (backing) image.

Signed-off-by: Uri Lublin <uril@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6908 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 24 insertions, 4 deletions

diff --git a/block.c b/block.c
index 7230f04..823841d 100644
--- a/block.c
+++ b/block.c
@@ -181,6 +181,20 @@ BlockDriver *bdrv_find_format(const char *format_name)
     return NULL;
 }
 
+int bdrv_create2(BlockDriver *drv,
+                const char *filename, int64_t size_in_sectors,
+                const char *backing_file, const char *backing_format,
+                int flags)
+{
+    if (drv->bdrv_create2)
+        return drv->bdrv_create2(filename, size_in_sectors, backing_file,
+                                 backing_format, flags);
+    if (drv->bdrv_create)
+        return drv->bdrv_create(filename, size_in_sectors, backing_file,
+                                flags);
+    return -ENOTSUP;
+}
+
 int bdrv_create(BlockDriver *drv,
                 const char *filename, int64_t size_in_sectors,
                 const char *backing_file, int flags)
@@ -357,7 +371,7 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
 
         /* if there is a backing file, use it */
         bs1 = bdrv_new("");
-        ret = bdrv_open(bs1, filename, 0);
+        ret = bdrv_open2(bs1, filename, 0, drv);
         if (ret < 0) {
             bdrv_delete(bs1);
             return ret;
@@ -378,12 +392,14 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
         else
             realpath(filename, backing_filename);
 
-        ret = bdrv_create(&bdrv_qcow2, tmp_filename,
-                          total_size, backing_filename, 0);
+        ret = bdrv_create2(&bdrv_qcow2, tmp_filename,
+                           total_size, backing_filename, 
+                           (drv ? drv->format_name : NULL), 0);
         if (ret < 0) {
             return ret;
         }
         filename = tmp_filename;
+        drv = &bdrv_qcow2;
         bs->is_temporary = 1;
     }
 
@@ -429,10 +445,14 @@ int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,
 #endif
     if (bs->backing_file[0] != '\0') {
         /* if there is a backing file, use it */
+        BlockDriver *back_drv = NULL;
         bs->backing_hd = bdrv_new("");
         path_combine(backing_filename, sizeof(backing_filename),
                      filename, bs->backing_file);
-        ret = bdrv_open(bs->backing_hd, backing_filename, open_flags);
+        if (bs->backing_format[0] != '\0')
+            back_drv = bdrv_find_format(bs->backing_format);
+        ret = bdrv_open2(bs->backing_hd, backing_filename, open_flags,
+                         back_drv);
         if (ret < 0) {
             bdrv_close(bs);
             return ret;