---
 drivers/md/dm-cache-target.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux/drivers/md/dm-cache-target.c
===================================================================
--- linux.orig/drivers/md/dm-cache-target.c
+++ linux/drivers/md/dm-cache-target.c
@@ -77,6 +77,7 @@ enum cache_mode {
 	CM_READ_ONLY,		/* metadata may not be changed */
 };
 
+// Support 'ignore_discard' like thin.
 struct cache_features {
 	enum cache_mode mode;
 	bool write_through:1;
@@ -1598,6 +1599,7 @@ static void init_features(struct cache_f
 	cf->write_through = false;
 }
 
+// Support ignore discards like thin
 static int parse_features(struct cache_args *ca, struct dm_arg_set *as,
 			  char **error)
 {
@@ -1619,6 +1621,7 @@ static int parse_features(struct cache_a
 	while (argc--) {
 		arg = dm_shift_arg(as);
 
+// FIXME Ban two conflicting args.  In fact, why do we need both at all?
 		if (!strcasecmp(arg, "writeback"))
 			cf->write_through = false;