block: add bdrv_open_backing_file

Mirroring runs without the backing file so that it can be copied outside QEMU. However, we need to add it at the time the job is completed and QEMU switches to the target. Factor out the common bits of opening an image and completing a mirroring operation. The new function does not assume that the file is closed immediately after it returns failure, so it keeps the BDRV_O_NO_BACKING flag up-to-date. Signed-off-by: Paolo Bonzini <[email protected]> Signed-off-by: Kevin Wolf <[email protected]>
0x3h · Oct 24, 2012 · 9156df1 · 9156df1
1 parent 9887b61
commit 9156df1
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Showing 2 changed files with 39 additions and 18 deletions.
diff --git a/block.c b/block.c
@@ -736,6 +736,42 @@ int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags)
     return 0;
 }
 
+int bdrv_open_backing_file(BlockDriverState *bs)
+{
+    char backing_filename[PATH_MAX];
+    int back_flags, ret;
+    BlockDriver *back_drv = NULL;
+
+    if (bs->backing_hd != NULL) {
+        return 0;
+    }
+
+    bs->open_flags &= ~BDRV_O_NO_BACKING;
+    if (bs->backing_file[0] == '\0') {
+        return 0;
+    }
+
+    bs->backing_hd = bdrv_new("");
+    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);
+    }
+
+    /* backing files always opened read-only */
+    back_flags = bs->open_flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT);
+
+    ret = bdrv_open(bs->backing_hd, backing_filename, back_flags, back_drv);
+    if (ret < 0) {
+        bdrv_delete(bs->backing_hd);
+        bs->backing_hd = NULL;
+        bs->open_flags |= BDRV_O_NO_BACKING;
+        return ret;
+    }
+    return 0;
+}
+
 /*
  * Opens a disk image (raw, qcow2, vmdk, ...)
  */
@@ -823,24 +859,8 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
     }
 
     /* If there is a backing file, use it */
-    if ((flags & BDRV_O_NO_BACKING) == 0 && bs->backing_file[0] != '\0') {
-        char backing_filename[PATH_MAX];
-        int back_flags;
-        BlockDriver *back_drv = NULL;
-
-        bs->backing_hd = bdrv_new("");
-        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);
-        }
-
-        /* backing files always opened read-only */
-        back_flags =
-            flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
-
-        ret = bdrv_open(bs->backing_hd, backing_filename, back_flags, back_drv);
+    if ((flags & BDRV_O_NO_BACKING) == 0) {
+        ret = bdrv_open_backing_file(bs);
         if (ret < 0) {
             bdrv_close(bs);
             return ret;

diff --git a/block.h b/block.h
@@ -133,6 +133,7 @@ void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top);
 void bdrv_delete(BlockDriverState *bs);
 int bdrv_parse_cache_flags(const char *mode, int *flags);
 int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags);
+int bdrv_open_backing_file(BlockDriverState *bs);
 int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
               BlockDriver *drv);
 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,