[PATCH v4 7/9] dm: handle error from blk_ksm_register()

[Satya Tangirala <satyaprateek2357@gmail.com>]

From: Satya Tangirala <satyat@google.com>

Handle any error from blk_ksm_register() in the callers. Previously,
the callers ignored the return value because blk_ksm_register() wouldn't
fail as long as the request_queue didn't have integrity support too, but
as this is no longer the case, it's safer for the callers to just handle
the return value appropriately.

Signed-off-by: Satya Tangirala <satyat@google.com>
---
 drivers/md/dm-table.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 29cbfc3e3c4b..c79c0fbe80dd 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1343,6 +1343,20 @@ static int dm_table_construct_keyslot_manager(struct dm_table *t)
 	 */
 	t->ksm = ksm;
 
+	/*
+	 * At this point, t->ksm is either NULL or *not* empty (i.e. will support
+	 * at least 1 crypto capability), the request queue doesn't support
+	 * integrity, and it also satisfies all the block layer constraints
+	 * "sufficiently" (as in the constraints of the DM device's request queue
+	 * won't preclude any of the intersection of the supported capabilities
+	 * of the underlying devices, since if some capability were precluded by
+	 * the DM device's request queue's constraints, that capability would
+	 * also have been precluded by one of the child device's request queues).
+	 *
+	 * Hence any future attempt to call blk_ksm_register() on t->ksm (if it's
+	 * not NULL) will succeed.
+	 */
+
 	return 0;
 }
 
@@ -1354,7 +1368,8 @@ static void dm_update_keyslot_manager(struct request_queue *q,
 
 	/* Make the ksm less restrictive */
 	if (!q->ksm) {
-		blk_ksm_register(t->ksm, q);
+		if (WARN_ON(!blk_ksm_register(t->ksm, q)))
+			dm_destroy_keyslot_manager(t->ksm);
 	} else {
 		blk_ksm_update_capabilities(q->ksm, t->ksm);
 		dm_destroy_keyslot_manager(t->ksm);
-- 
2.25.1