[PATCH v4 4/5] dm: support key eviction from keyslot managers of underlying devices

[Satya Tangirala <satyat@google.com>]

Now that device mapper supports inline encryption, add the ability to
evict keys from all underlying devices. When an upper layer requests
a key eviction, we simply iterate through all underlying devices
and evict that key from each device.

Co-developed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
---
 block/blk-crypto.c    |  1 +
 drivers/md/dm-table.c | 53 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 5da43f0973b4..c2be8f15006c 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -409,3 +409,4 @@ int blk_crypto_evict_key(struct request_queue *q,
 	 */
 	return blk_crypto_fallback_evict_key(key);
 }
+EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index b37f69343923..3eacc5329603 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1214,6 +1214,58 @@ struct dm_keyslot_manager {
 	struct mapped_device *md;
 };
 
+struct dm_keyslot_evict_args {
+	const struct blk_crypto_key *key;
+	int err;
+};
+
+static int dm_keyslot_evict_callback(struct dm_target *ti, struct dm_dev *dev,
+				     sector_t start, sector_t len, void *data)
+{
+	struct dm_keyslot_evict_args *args = data;
+	int err;
+
+	err = blk_crypto_evict_key(bdev_get_queue(dev->bdev), args->key);
+	if (!args->err)
+		args->err = err;
+	/* Always try to evict the key from all devices. */
+	return 0;
+}
+
+/*
+ * When an inline encryption key is evicted from a device-mapper device, evict
+ * it from all the underlying devices.
+ */
+static int dm_keyslot_evict(struct blk_keyslot_manager *ksm,
+			    const struct blk_crypto_key *key, unsigned int slot)
+{
+	struct dm_keyslot_manager *dksm = container_of(ksm,
+						       struct dm_keyslot_manager,
+						       ksm);
+	struct mapped_device *md = dksm->md;
+	struct dm_keyslot_evict_args args = { key };
+	struct dm_table *t;
+	int srcu_idx;
+	int i;
+	struct dm_target *ti;
+
+	t = dm_get_live_table(md, &srcu_idx);
+	if (!t)
+		return 0;
+	for (i = 0; i < dm_table_get_num_targets(t); i++) {
+		ti = dm_table_get_target(t, i);
+		if (!ti->type->iterate_devices)
+			continue;
+		ti->type->iterate_devices(ti, dm_keyslot_evict_callback, &args);
+	}
+	dm_put_live_table(md, srcu_idx);
+	return args.err;
+}
+
+static struct blk_ksm_ll_ops dm_ksm_ll_ops = {
+	.keyslot_evict = dm_keyslot_evict,
+};
+
 static int device_intersect_crypto_modes(struct dm_target *ti,
 					 struct dm_dev *dev, sector_t start,
 					 sector_t len, void *data)
@@ -1269,6 +1321,7 @@ dm_table_construct_keyslot_manager(struct dm_table *t)
 
 	ksm = &dksm->ksm;
 	blk_ksm_init_passthrough(ksm);
+	ksm->ksm_ll_ops = dm_ksm_ll_ops;
 	ksm->max_dun_bytes_supported = UINT_MAX;
 	memset(ksm->crypto_modes_supported, 0xFF,
 	       sizeof(ksm->crypto_modes_supported));
-- 
2.30.0.365.g02bc693789-goog