block: Allow references for backing files
For bs->file, using references to existing BDSes has been possible for a
while already. This patch enables the same for bs->backing.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
diff --git a/block.c b/block.c
index 57bf8fc..84b9bf4 100644
--- a/block.c
+++ b/block.c
@@ -1182,30 +1182,43 @@
/*
* Opens the backing file for a BlockDriverState if not yet open
*
- * options is a QDict of options to pass to the block drivers, or NULL for an
- * empty set of options. The reference to the QDict is transferred to this
- * function (even on failure), so if the caller intends to reuse the dictionary,
- * it needs to use QINCREF() before calling bdrv_file_open.
+ * bdref_key specifies the key for the image's BlockdevRef in the options QDict.
+ * That QDict has to be flattened; therefore, if the BlockdevRef is a QDict
+ * itself, all options starting with "${bdref_key}." are considered part of the
+ * BlockdevRef.
+ *
+ * TODO Can this be unified with bdrv_open_image()?
*/
-int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp)
+int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
+ const char *bdref_key, Error **errp)
{
char *backing_filename = g_malloc0(PATH_MAX);
+ char *bdref_key_dot;
+ const char *reference = NULL;
int ret = 0;
BlockDriverState *backing_hd;
+ QDict *options;
+ QDict *tmp_parent_options = NULL;
Error *local_err = NULL;
if (bs->backing != NULL) {
- QDECREF(options);
goto free_exit;
}
/* NULL means an empty set of options */
- if (options == NULL) {
- options = qdict_new();
+ if (parent_options == NULL) {
+ tmp_parent_options = qdict_new();
+ parent_options = tmp_parent_options;
}
bs->open_flags &= ~BDRV_O_NO_BACKING;
- if (qdict_haskey(options, "file.filename")) {
+
+ bdref_key_dot = g_strdup_printf("%s.", bdref_key);
+ qdict_extract_subqdict(parent_options, &options, bdref_key_dot);
+ g_free(bdref_key_dot);
+
+ reference = qdict_get_try_str(parent_options, bdref_key);
+ if (reference || qdict_haskey(options, "file.filename")) {
backing_filename[0] = '\0';
} else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
QDECREF(options);
@@ -1228,19 +1241,16 @@
goto free_exit;
}
- backing_hd = bdrv_new();
-
if (bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
qdict_put(options, "driver", qstring_from_str(bs->backing_format));
}
- assert(bs->backing == NULL);
+ backing_hd = NULL;
ret = bdrv_open_inherit(&backing_hd,
*backing_filename ? backing_filename : NULL,
- NULL, options, 0, bs, &child_backing, &local_err);
+ reference, options, 0, bs, &child_backing,
+ &local_err);
if (ret < 0) {
- bdrv_unref(backing_hd);
- backing_hd = NULL;
bs->open_flags |= BDRV_O_NO_BACKING;
error_setg(errp, "Could not open backing file: %s",
error_get_pretty(local_err));
@@ -1253,8 +1263,11 @@
bdrv_set_backing_hd(bs, backing_hd);
bdrv_unref(backing_hd);
+ qdict_del(parent_options, bdref_key);
+
free_exit:
g_free(backing_filename);
+ QDECREF(tmp_parent_options);
return ret;
}
@@ -1537,10 +1550,7 @@
/* If there is a backing file, use it */
if ((flags & BDRV_O_NO_BACKING) == 0) {
- QDict *backing_options;
-
- qdict_extract_subqdict(options, &backing_options, "backing.");
- ret = bdrv_open_backing_file(bs, backing_options, &local_err);
+ ret = bdrv_open_backing_file(bs, options, "backing", &local_err);
if (ret < 0) {
goto close_and_fail;
}
