dm table: allow targets to support discards internally
Permit a target to support discards regardless of whether or not all its
underlying devices do.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index cb8380c..215e112 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1346,7 +1346,8 @@
return 0;
/*
- * Ensure that at least one underlying device supports discards.
+ * Unless any target used by the table set discards_supported,
+ * require at least one underlying device to support discards.
* t->devices includes internal dm devices such as mirror logs
* so we need to use iterate_devices here, which targets
* supporting discard must provide.
@@ -1354,6 +1355,9 @@
while (i < dm_table_get_num_targets(t)) {
ti = dm_table_get_target(t, i++);
+ if (ti->discards_supported)
+ return 1;
+
if (ti->type->iterate_devices &&
ti->type->iterate_devices(ti, device_discard_capable, NULL))
return 1;
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 32a4423..4427e04 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -191,6 +191,12 @@
/* Used to provide an error string from the ctr */
char *error;
+
+ /*
+ * Set if this target needs to receive discards regardless of
+ * whether or not its underlying devices have support.
+ */
+ unsigned discards_supported:1;
};
/* Each target can link one of these into the table */