block: Require auto-read-only for existing fallbacks
Some block drivers have traditionally changed their node to read-only
mode without asking the user. This behaviour has been marked deprecated
since 2.11, expecting users to provide an explicit read-only=on option.
Now that we have auto-read-only=on, enable these drivers to make use of
the option.
This is the only use of bdrv_set_read_only(), so we can make it a bit
more specific and turn it into a bdrv_apply_auto_read_only() that is
more convenient for drivers to use.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/block.c b/block.c
index 96090c3..fd67e14 100644
--- a/block.c
+++ b/block.c
@@ -266,29 +266,41 @@
return 0;
}
-/* TODO Remove (deprecated since 2.11)
- * Block drivers are not supposed to automatically change bs->read_only.
- * Instead, they should just check whether they can provide what the user
- * explicitly requested and error out if read-write is requested, but they can
- * only provide read-only access. */
-int bdrv_set_read_only(BlockDriverState *bs, bool read_only, Error **errp)
+/*
+ * Called by a driver that can only provide a read-only image.
+ *
+ * Returns 0 if the node is already read-only or it could switch the node to
+ * read-only because BDRV_O_AUTO_RDONLY is set.
+ *
+ * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set
+ * or bdrv_can_set_read_only() forbids making the node read-only. If @errmsg
+ * is not NULL, it is used as the error message for the Error object.
+ */
+int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
+ Error **errp)
{
int ret = 0;
- ret = bdrv_can_set_read_only(bs, read_only, false, errp);
+ if (!(bs->open_flags & BDRV_O_RDWR)) {
+ return 0;
+ }
+ if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
+ goto fail;
+ }
+
+ ret = bdrv_can_set_read_only(bs, true, false, NULL);
if (ret < 0) {
- return ret;
+ goto fail;
}
- bs->read_only = read_only;
-
- if (read_only) {
- bs->open_flags &= ~BDRV_O_RDWR;
- } else {
- bs->open_flags |= BDRV_O_RDWR;
- }
+ bs->read_only = true;
+ bs->open_flags &= ~BDRV_O_RDWR;
return 0;
+
+fail:
+ error_setg(errp, "%s", errmsg ?: "Image is read-only");
+ return -EACCES;
}
void bdrv_get_full_backing_filename_from_filename(const char *backed,
