block: rename .bdrv_create() to .bdrv_co_create_opts()

BlockDriver->bdrv_create() has been called from coroutine context since
commit 5b7e1542cfa41a281af9629d31cef03704d976e6 ("block: make
bdrv_create adopt coroutine").

Make this explicit by renaming to .bdrv_co_create_opts() and add the
coroutine_fn annotation.  This makes it obvious to block driver authors
that they may yield, use CoMutex, or other coroutine_fn APIs.
bdrv_co_create is reserved for the QAPI-based version that Kevin is
working on.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170705102231.20711-2-stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block/qcow2.c b/block/qcow2.c
index 288b529..93fb625 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -2916,7 +2916,8 @@
     return ret;
 }
 
-static int qcow2_create(const char *filename, QemuOpts *opts, Error **errp)
+static int coroutine_fn qcow2_co_create_opts(const char *filename, QemuOpts *opts,
+                                             Error **errp)
 {
     char *backing_file = NULL;
     char *backing_fmt = NULL;
@@ -4352,7 +4353,7 @@
     .bdrv_reopen_abort    = qcow2_reopen_abort,
     .bdrv_join_options    = qcow2_join_options,
     .bdrv_child_perm      = bdrv_format_default_perms,
-    .bdrv_create        = qcow2_create,
+    .bdrv_co_create_opts  = qcow2_co_create_opts,
     .bdrv_has_zero_init = bdrv_has_zero_init_1,
     .bdrv_co_block_status = qcow2_co_block_status,