bio-integrity: add "bip_max_vcnt" into struct bio_integrity_payload

Commit 08778795 ("block: Fix nr_vecs for inline integrity vectors") from
Martin introduces the function bip_integrity_vecs(get the useful vectors)
to fix the issue about nr_vecs for inline integrity vectors that reported
by David Milburn.

But it seems that bip_integrity_vecs() will return the wrong number if the
bio is not based on any bio_set for some reason(bio->bi_pool == NULL),
because in that case, the bip_inline_vecs[0] is malloced directly.  So
here we add the bip_max_vcnt to record the count of vector slots, and
cleanup the function bip_integrity_vecs().
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/bio-integrity.c

@@ -70,8 +70,10 @@ struct bio_integrity_payload *bio_integrity_alloc(struct bio *bio,
 					  bs->bvec_integrity_pool);
 		if (!bip->bip_vec)
 			goto err;
+		bip->bip_max_vcnt = bvec_nr_vecs(idx);
 	} else {
 		bip->bip_vec = bip->bip_inline_vecs;
+		bip->bip_max_vcnt = inline_vecs;
 	}
 
 	bip->bip_slab = idx;
@@ -114,14 +116,6 @@ void bio_integrity_free(struct bio *bio)
 }
 EXPORT_SYMBOL(bio_integrity_free);
 
-static inline unsigned int bip_integrity_vecs(struct bio_integrity_payload *bip)
-{
-	if (bip->bip_slab == BIO_POOL_NONE)
-		return BIP_INLINE_VECS;
-
-	return bvec_nr_vecs(bip->bip_slab);
-}
-
 /**
  * bio_integrity_add_page - Attach integrity metadata
  * @bio:	bio to update
@@ -137,7 +131,7 @@ int bio_integrity_add_page(struct bio *bio, struct page *page,
 	struct bio_integrity_payload *bip = bio->bi_integrity;
 	struct bio_vec *iv;
 
-	if (bip->bip_vcnt >= bip_integrity_vecs(bip)) {
+	if (bip->bip_vcnt >= bip->bip_max_vcnt) {
 		printk(KERN_ERR "%s: bip_vec full\n", __func__);
 		return 0;
 	}

include/linux/bio.h

@@ -308,6 +308,7 @@ struct bio_integrity_payload {
 
 	unsigned short		bip_slab;	/* slab the bip came from */
 	unsigned short		bip_vcnt;	/* # of integrity bio_vecs */
+	unsigned short		bip_max_vcnt;	/* integrity bio_vec slots */
 	unsigned		bip_owns_buf:1;	/* should free bip_buf */
 
 	struct work_struct	bip_work;	/* I/O completion */