qcow2: make qcow2_co_create2() a coroutine_fn

qcow2_create2() calls qemu_co_mutex_lock().  Only a coroutine_fn may
call another coroutine_fn.  In fact, qcow2_create2 is always called from
coroutine context.

Rename the function to add the "co" moniker and add coroutine_fn.
Reported-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170705102231.20711-3-stefanha@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2.c

@@ -2725,11 +2725,12 @@ static uint64_t qcow2_opt_get_refcount_bits_del(QemuOpts *opts, int version,
     return refcount_bits;
 }
 
-static int qcow2_create2(const char *filename, int64_t total_size,
-                         const char *backing_file, const char *backing_format,
-                         int flags, size_t cluster_size, PreallocMode prealloc,
-                         QemuOpts *opts, int version, int refcount_order,
-                         const char *encryptfmt, Error **errp)
+static int coroutine_fn
+qcow2_co_create2(const char *filename, int64_t total_size,
+                 const char *backing_file, const char *backing_format,
+                 int flags, size_t cluster_size, PreallocMode prealloc,
+                 QemuOpts *opts, int version, int refcount_order,
+                 const char *encryptfmt, Error **errp)
 {
     QDict *options;
 
@@ -2998,9 +2999,9 @@ static int coroutine_fn qcow2_co_create_opts(const char *filename, QemuOpts *opt
 
     refcount_order = ctz32(refcount_bits);
 
-    ret = qcow2_create2(filename, size, backing_file, backing_fmt, flags,
-                        cluster_size, prealloc, opts, version, refcount_order,
-                        encryptfmt, &local_err);
+    ret = qcow2_co_create2(filename, size, backing_file, backing_fmt, flags,
+                           cluster_size, prealloc, opts, version, refcount_order,
+                           encryptfmt, &local_err);
     error_propagate(errp, local_err);
 
 finish: