[PATCH v2 07/26] block: Don't use bi_idx in bio_split() or require it to be 0

[Kent Overstreet <koverstreet@google.com>]

Prep work for immutable bio_vecs/efficient bio splitting: they require
auditing and removing most uses of bi_idx.

So here we convert bio_split() to respect the current value of bi_idx
and use the bio_iovec() macro, instead of assuming bi_idx will be 0.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
---
 drivers/block/drbd/drbd_req.c | 6 +++---
 drivers/md/raid0.c            | 3 +--
 drivers/md/raid10.c           | 3 +--
 fs/bio-integrity.c            | 4 ++--
 fs/bio.c                      | 7 +++----
 5 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index af69a96..57eb253 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1155,11 +1155,11 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
 
 	/* can this bio be split generically?
 	 * Maybe add our own split-arbitrary-bios function. */
-	if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_BIO_SIZE) {
+	if (bio_segments(bio) != 1 || bio->bi_size > DRBD_MAX_BIO_SIZE) {
 		/* rather error out here than BUG in bio_split */
 		dev_err(DEV, "bio would need to, but cannot, be split: "
-		    "(vcnt=%u,idx=%u,size=%u,sector=%llu)\n",
-		    bio->bi_vcnt, bio->bi_idx, bio->bi_size,
+		    "(segments=%u,size=%u,sector=%llu)\n",
+		    bio_segments(bio), bio->bi_size,
 		    (unsigned long long)bio->bi_sector);
 		bio_endio(bio, -EINVAL);
 	} else {
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 387cb89..0587450 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -509,8 +509,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 		sector_t sector = bio->bi_sector;
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if (bio->bi_vcnt != 1 ||
-		    bio->bi_idx != 0)
+		if (bio_segments(bio) != 1)
 			goto bad_map;
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9715aaf..bbd08f5 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1081,8 +1081,7 @@ static void make_request(struct mddev *mddev, struct bio * bio)
 			 || conf->prev.near_copies < conf->prev.raid_disks))) {
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if (bio->bi_vcnt != 1 ||
-		    bio->bi_idx != 0)
+		if (bio_segments(bio) != 1)
 			goto bad_map;
 		/* This is a one page bio that upper layers
 		 * refuse to split for us, so we need to split it.
diff --git a/fs/bio-integrity.c b/fs/bio-integrity.c
index 1d64f7f..e8555a5 100644
--- a/fs/bio-integrity.c
+++ b/fs/bio-integrity.c
@@ -657,8 +657,8 @@ void bio_integrity_split(struct bio *bio, struct bio_pair *bp, int sectors)
 	bp->bio1.bi_integrity = &bp->bip1;
 	bp->bio2.bi_integrity = &bp->bip2;
 
-	bp->iv1 = bip->bip_vec[0];
-	bp->iv2 = bip->bip_vec[0];
+	bp->iv1 = bip->bip_vec[bip->bip_idx];
+	bp->iv2 = bip->bip_vec[bip->bip_idx];
 
 	bp->bip1.bip_vec = &bp->iv1;
 	bp->bip2.bip_vec = &bp->iv2;
diff --git a/fs/bio.c b/fs/bio.c
index 07587c0..addeac2 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1616,8 +1616,7 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	trace_block_split(bdev_get_queue(bi->bi_bdev), bi,
 				bi->bi_sector + first_sectors);
 
-	BUG_ON(bi->bi_vcnt != 1);
-	BUG_ON(bi->bi_idx != 0);
+	BUG_ON(bio_segments(bi) != 1);
 	atomic_set(&bp->cnt, 3);
 	bp->error = 0;
 	bp->bio1 = *bi;
@@ -1626,8 +1625,8 @@ struct bio_pair *bio_split(struct bio *bi, int first_sectors)
 	bp->bio2.bi_size -= first_sectors << 9;
 	bp->bio1.bi_size = first_sectors << 9;
 
-	bp->bv1 = bi->bi_io_vec[0];
-	bp->bv2 = bi->bi_io_vec[0];
+	bp->bv1 = *bio_iovec(bi);
+	bp->bv2 = *bio_iovec(bi);
 	bp->bv2.bv_offset += first_sectors << 9;
 	bp->bv2.bv_len -= first_sectors << 9;
 	bp->bv1.bv_len = first_sectors << 9;
-- 
1.7.12