block: Introduce integrity data ownership flag

A filesystem might supply its own integrity metadata.  Introduce a
flag that indicates whether the filesystem or the block layer owns the
integrity buffer.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

fs/bio-integrity.c

@@ -107,7 +107,8 @@ void bio_integrity_free(struct bio *bio, struct bio_set *bs)
 	BUG_ON(bip == NULL);
 
 	/* A cloned bio doesn't own the integrity metadata */
-	if (!bio_flagged(bio, BIO_CLONED) && bip->bip_buf != NULL)
+	if (!bio_flagged(bio, BIO_CLONED) && !bio_flagged(bio, BIO_FS_INTEGRITY)
+	    && bip->bip_buf != NULL)
 		kfree(bip->bip_buf);
 
 	mempool_free(bip->bip_vec, bs->bvec_pools[bip->bip_pool]);

include/linux/bio.h

@@ -109,6 +109,7 @@ struct bio {
 #define BIO_EOPNOTSUPP	7	/* not supported */
 #define BIO_CPU_AFFINE	8	/* complete bio on same CPU as submitted */
 #define BIO_NULL_MAPPED 9	/* contains invalid user pages */
+#define BIO_FS_INTEGRITY 10	/* fs owns integrity data, not block layer */
 #define bio_flagged(bio, flag)	((bio)->bi_flags & (1 << (flag)))
 
 /*