block: centralize PI remapping logic to the block layer

Currently t10_pi_prepare/t10_pi_complete functions are called during the
NVMe and SCSi layers command preparetion/completion, but their actual
place should be the block layer since T10-PI is a general data integrity
feature that is used by block storage protocols. Introduce .prepare_fn
and .complete_fn callbacks within the integrity profile that each type
can implement according to its needs.

Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Suggested-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>

Fixed to not call queue integrity functions if BLK_DEV_INTEGRITY
isn't defined in the config.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm-integrity.c

@@ -345,6 +345,14 @@ static void __DEBUG_bytes(__u8 *bytes, size_t len, const char *msg, ...)
 #define DEBUG_bytes(bytes, len, msg, ...)	do { } while (0)
 #endif
 
+static void dm_integrity_prepare(struct request *rq)
+{
+}
+
+static void dm_integrity_complete(struct request *rq, unsigned int nr_bytes)
+{
+}
+
 /*
  * DM Integrity profile, protection is performed layer above (dm-crypt)
  */
@@ -352,6 +360,8 @@ static const struct blk_integrity_profile dm_integrity_profile = {
 	.name			= "DM-DIF-EXT-TAG",
 	.generate_fn		= NULL,
 	.verify_fn		= NULL,
+	.prepare_fn		= dm_integrity_prepare,
+	.complete_fn		= dm_integrity_complete,
 };
 
 static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map);