dm: allow targets to return output from messages they are sent
Could be useful for a target to return stats or other information.
If a target does DMEMIT() anything to @result from its .message method
then it must return 1 to the caller.
Signed-off-By: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
index 8d0ba87..8f9208c 100644
--- a/drivers/md/dm-switch.c
+++ b/drivers/md/dm-switch.c
@@ -466,7 +466,8 @@ static int process_set_region_mappings(struct switch_ctx *sctx,
*
* Only set_region_mappings is supported.
*/
-static int switch_message(struct dm_target *ti, unsigned argc, char **argv)
+static int switch_message(struct dm_target *ti, unsigned argc, char **argv,
+ char *result, unsigned maxlen)
{
static DEFINE_MUTEX(message_mutex);