block: Deprecate bdrv_set_read_only() and users

bdrv_set_read_only() is used by some block drivers to override the
read-only option given by the user. This is not how read-only images
generally work in QEMU: Instead of second guessing what the user really
meant (which currently includes making an image read-only even if the
user didn't only use the default, but explicitly said read-only=off), we
should error out if we can't provide what the user requested.

This adds deprecation warnings to all callers of bdrv_set_read_only() so
that the behaviour can be corrected after the usual deprecation period.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/block.c b/block.c
index f6415547fe..0ed0c27140 100644
--- a/block.c
+++ b/block.c
@@ -261,6 +261,11 @@ int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
     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)
 {
     int ret = 0;