dm: introduce split_discard_requests
This patch introduces a new variable split_discard_requests. It can be
set by targets so that discard requests are split on max_io_len
boundaries.
When split_discard_requests is not set, discard requests are only split on
boundaries between targets, as was the case before this patch.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 415c280..4e09b6f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1215,7 +1215,10 @@
if (!ti->num_discard_requests)
return -EOPNOTSUPP;
- len = min(ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
+ if (!ti->split_discard_requests)
+ len = min(ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
+ else
+ len = min(ci->sector_count, max_io_len(ci->sector, ti));
__issue_target_requests(ci, ti, ti->num_discard_requests, len);
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index b19c1e1..8bdbbfc 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -218,6 +218,12 @@
unsigned discards_supported:1;
/*
+ * Set if the target required discard request to be split
+ * on max_io_len boundary.
+ */
+ unsigned split_discard_requests:1;
+
+ /*
* Set if this target does not return zeroes on discarded blocks.
*/
unsigned discard_zeroes_data_unsupported:1;