dm table: add flag to allow target to handle its own integrity metadata

Add DM_TARGET_INTEGRITY flag that specifies bio integrity metadata is
not inherited but implemented in the target itself.

Signed-off-by: Milan Broz <[e-mail]>
Signed-off-by: Mike Snitzer <[e-mail]>

drivers/md/dm-table.c

···
 	bool integrity_supported:1;
 	bool singleton:1;
 	bool all_blk_mq:1;
+	unsigned integrity_added:1;
 
 	/*
 	 * Indicates the rw permissions for the new logical
···
 		t->immutable_target_type = tgt->type;
 	}
 
+	if (dm_target_has_integrity(tgt->type))
+		t->integrity_added = 1;
+
 	tgt->table = t;
 	tgt->begin = start;
 	tgt->len = len;
···
 	struct mapped_device *md = t->md;
 	struct gendisk *template_disk = NULL;
 
+	/* If target handles integrity itself do not register it here. */
+	if (t->integrity_added)
+		return 0;
+
 	template_disk = dm_table_get_integrity_disk(t);
 	if (!template_disk)
 		return 0;
···
 static void dm_table_verify_integrity(struct dm_table *t)
 {
 	struct gendisk *template_disk = NULL;
+
+	if (t->integrity_added)
+		return;
 
 	if (t->integrity_supported) {
 		/*

include/linux/device-mapper.h

···
  */
 typedef unsigned (*dm_num_write_bios_fn) (struct dm_target *ti, struct bio *bio);
 
+/*
+ * A target implements own bio data integrity.
+ */
+#define DM_TARGET_INTEGRITY		0x00000010
+#define dm_target_has_integrity(type)	((type)->features & DM_TARGET_INTEGRITY)
+
 struct dm_target {
 	struct dm_table *table;
 	struct target_type *type;