dm: add support for passing through inline crypto support

Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.

This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support.  When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices.  When an unsupported setting is used, the blk-crypto
fallback is used as usual.

Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it.  This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target.  Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't.  (dm-crypt could use inline crypto itself, though.)

A DM device's table can only be changed if the "new" inline encryption
capabilities are a (*not* necessarily strict) superset of the "old" inline
encryption capabilities.  Attempts to make changes to the table that result
in some inline encryption capability becoming no longer supported will be
rejected.

For the sake of clarity, key eviction from underlying devices will be
handled in a future patch.

Co-developed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 64fda1429e39..7021aea82aa4 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -28,6 +28,7 @@
 #include <linux/refcount.h>
 #include <linux/part_stat.h>
 #include <linux/blk-crypto.h>
+#include <linux/keyslot-manager.h>
 
 #define DM_MSG_PREFIX "core"
 
@@ -1722,6 +1723,19 @@ static const struct dax_operations dm_dax_ops;
 
 static void dm_wq_work(struct work_struct *work);
 
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+static void dm_queue_destroy_keyslot_manager(struct request_queue *q)
+{
+	dm_destroy_keyslot_manager(q->ksm);
+}
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline void dm_queue_destroy_keyslot_manager(struct request_queue *q)
+{
+}
+#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
 static void cleanup_mapped_device(struct mapped_device *md)
 {
 	if (md->wq)
@@ -1743,8 +1757,10 @@ static void cleanup_mapped_device(struct mapped_device *md)
 		put_disk(md->disk);
 	}
 
-	if (md->queue)
+	if (md->queue) {
+		dm_queue_destroy_keyslot_manager(md->queue);
 		blk_cleanup_queue(md->queue);
+	}
 
 	cleanup_srcu_struct(&md->io_barrier);