Fix memory leak in zvol_set_volsize()

Move kmem_free() so it's called for every error path: this is
preferred over making `dmu_object_info_t doi` local to accommodate
older kernels with limited stacks.

Reviewed by: Boris Protopopov <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Giuseppe Di Natale <[email protected]>
Signed-off-by: loli10K <[email protected]>
Closes openzfs#6177

Author: loli10K

module/zfs/zvol.c

@@ -419,11 +419,12 @@ zvol_set_volsize(const char *name, uint64_t volsize)
 		goto out;
 
 	error = zvol_update_volsize(volsize, os);
-	kmem_free(doi, sizeof (dmu_object_info_t));
 
 	if (error == 0 && zv != NULL)
 		error = zvol_update_live_volsize(zv, volsize);
 out:
+	kmem_free(doi, sizeof (dmu_object_info_t));
+
 	if (owned) {
 		dmu_objset_disown(os, FTAG);
 		if (zv != NULL)