block: Add reference parameter to bdrv_open()
Allow bdrv_open() to handle references to existing block devices just as
bdrv_file_open() is already capable of.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index c39bd3d..86a32e7 100644
--- a/block.c
+++ b/block.c
@@ -1046,7 +1046,7 @@
}
if (!drv->bdrv_file_open) {
- ret = bdrv_open(&bs, filename, options, flags, drv, &local_err);
+ ret = bdrv_open(&bs, filename, NULL, options, flags, drv, &local_err);
options = NULL;
} else {
ret = bdrv_open_common(bs, NULL, options, flags, drv, &local_err);
@@ -1125,7 +1125,7 @@
assert(bs->backing_hd == NULL);
ret = bdrv_open(&bs->backing_hd,
- *backing_filename ? backing_filename : NULL, options,
+ *backing_filename ? backing_filename : NULL, NULL, options,
back_flags, back_drv, &local_err);
if (ret < 0) {
bs->backing_hd = NULL;
@@ -1206,7 +1206,7 @@
goto done;
}
- ret = bdrv_open(pbs, filename, image_options, flags, NULL, errp);
+ ret = bdrv_open(pbs, filename, NULL, image_options, flags, NULL, errp);
} else {
ret = bdrv_file_open(pbs, filename, reference, image_options, flags,
errp);
@@ -1227,9 +1227,14 @@
*
* If *pbs is NULL, a new BDS will be created with a pointer to it stored there.
* If it is not NULL, the referenced BDS will be reused.
+ *
+ * The reference parameter may be used to specify an existing block device which
+ * should be opened. If specified, neither options nor a filename may be given,
+ * nor can an existing BDS be reused (that is, *pbs has to be NULL).
*/
-int bdrv_open(BlockDriverState **pbs, const char *filename, QDict *options,
- int flags, BlockDriver *drv, Error **errp)
+int bdrv_open(BlockDriverState **pbs, const char *filename,
+ const char *reference, QDict *options, int flags,
+ BlockDriver *drv, Error **errp)
{
int ret;
/* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */
@@ -1240,6 +1245,31 @@
assert(pbs);
+ if (reference) {
+ bool options_non_empty = options ? qdict_size(options) : false;
+ QDECREF(options);
+
+ if (*pbs) {
+ error_setg(errp, "Cannot reuse an existing BDS when referencing "
+ "another block device");
+ return -EINVAL;
+ }
+
+ if (filename || options_non_empty) {
+ error_setg(errp, "Cannot reference an existing block device with "
+ "additional options or a new filename");
+ return -EINVAL;
+ }
+
+ bs = bdrv_lookup_bs(reference, reference, errp);
+ if (!bs) {
+ return -ENODEV;
+ }
+ bdrv_ref(bs);
+ *pbs = bs;
+ return 0;
+ }
+
if (*pbs) {
bs = *pbs;
} else {
@@ -1268,7 +1298,7 @@
/* Get the required size from the image */
QINCREF(options);
bs1 = NULL;
- ret = bdrv_open(&bs1, filename, options, BDRV_O_NO_BACKING,
+ ret = bdrv_open(&bs1, filename, NULL, options, BDRV_O_NO_BACKING,
drv, &local_err);
if (ret < 0) {
goto fail;
@@ -5309,7 +5339,7 @@
flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
bs = NULL;
- ret = bdrv_open(&bs, backing_file->value.s, NULL, back_flags,
+ ret = bdrv_open(&bs, backing_file->value.s, NULL, NULL, back_flags,
backing_drv, &local_err);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not open '%s': %s",
