blk-integrity: empty implementation when disabled

This patch moves the blk_integrity_payload definition outside the
CONFIG_BLK_DEV_INTERITY dependency and provides empty function
implementations when the kernel configuration disables integrity
extensions. This simplifies drivers that make use of these to map user
data so they don't need to repeat the same configuration checks.

Signed-off-by: Keith Busch <keith.busch@intel.com>

Updated by Jens to pass an error pointer return from
bio_integrity_alloc(), otherwise if CONFIG_BLK_DEV_INTEGRITY isn't
set, we return a weird ENOMEM from __nvme_submit_user_cmd()
if a meta buffer is set.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/bio-integrity.c b/block/bio-integrity.c
index f6325d5..e6ba501 100644
--- a/block/bio-integrity.c
+++ b/block/bio-integrity.c
@@ -66,7 +66,7 @@
 	}
 
 	if (unlikely(!bip))
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	memset(bip, 0, sizeof(*bip));
 
@@ -89,7 +89,7 @@
 	return bip;
 err:
 	mempool_free(bip, bs->bio_integrity_pool);
-	return NULL;
+	return ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL(bio_integrity_alloc);
 
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c61bde9..f9c4e80 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -190,8 +190,8 @@
 			}
 
 			bip = bio_integrity_alloc(bio, GFP_KERNEL, 1);
-			if (!bip) {
-				ret = -ENOMEM;
+			if (IS_ERR(bip)) {
+				ret = PTR_ERR(bip);
 				goto out_free_meta;
 			}
 
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index f29c691..d5891b6 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -613,9 +613,9 @@
 	}
 
 	bip = bio_integrity_alloc(bio, GFP_NOIO, cmd->t_prot_nents);
-	if (!bip) {
+	if (IS_ERR(bip)) {
 		pr_err("Unable to allocate bio_integrity_payload\n");
-		return -ENOMEM;
+		return PTR_ERR(bip);
 	}
 
 	bip->bip_iter.bi_size = (cmd->data_length / dev->dev_attrib.block_size) *
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b9b6e04..5349e68 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -318,16 +318,6 @@
 	BIP_IP_CHECKSUM		= 1 << 4, /* IP checksum */
 };
 
-#if defined(CONFIG_BLK_DEV_INTEGRITY)
-
-static inline struct bio_integrity_payload *bio_integrity(struct bio *bio)
-{
-	if (bio->bi_rw & REQ_INTEGRITY)
-		return bio->bi_integrity;
-
-	return NULL;
-}
-
 /*
  * bio integrity payload
  */
@@ -349,6 +339,16 @@
 	struct bio_vec		bip_inline_vecs[0];/* embedded bvec array */
 };
 
+#if defined(CONFIG_BLK_DEV_INTEGRITY)
+
+static inline struct bio_integrity_payload *bio_integrity(struct bio *bio)
+{
+	if (bio->bi_rw & REQ_INTEGRITY)
+		return bio->bi_integrity;
+
+	return NULL;
+}
+
 static inline bool bio_integrity_flagged(struct bio *bio, enum bip_flags flag)
 {
 	struct bio_integrity_payload *bip = bio_integrity(bio);
@@ -795,6 +795,18 @@
 	return false;
 }
 
+static inline void *bio_integrity_alloc(struct bio * bio, gfp_t gfp,
+								unsigned int nr)
+{
+	return ERR_PTR(-EINVAL);
+}
+
+static inline int bio_integrity_add_page(struct bio *bio, struct page *page,
+					unsigned int len, unsigned int offset)
+{
+	return 0;
+}
+
 #endif /* CONFIG_BLK_DEV_INTEGRITY */
 
 #endif /* CONFIG_BLOCK */