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>

1 files changed, 6 insertions, 0 deletions

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 @@ struct dm_target {
 
 	/* 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 */