block: Kill bio_segments()/bi_vcnt usage

When we start sharing biovecs, keeping bi_vcnt accurate for splits is
going to be error prone - and unnecessary, if we refactor some code.

So bio_segments() has to go - but most of the existing users just needed
to know if the bio had multiple segments, which is easier - add a
bio_multiple_segments() for them.

(Two of the current uses of bio_segments() are going to go away in a
couple patches, but the current implementation of bio_segments() is
unsafe as soon as we start doing driver conversions for immutable
biovecs - so implement a dumb version for bisectability, it'll go away
in a couple patches)

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Neil Brown <neilb@suse.de>
Cc: Nagalakshmi Nandigama <Nagalakshmi.Nandigama@lsi.com>
Cc: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>

8 files changed, 45 insertions, 53 deletions

diff --git a/drivers/block/ps3disk.c b/drivers/block/ps3disk.c
index 1c6edb9a9960..c120d70d3fb3 100644
--- a/drivers/block/ps3disk.c
+++ b/drivers/block/ps3disk.c
@@ -101,10 +101,9 @@ static void ps3disk_scatter_gather(struct ps3_storage_device *dev,
 
 	rq_for_each_segment(bvec, req, iter) {
 		unsigned long flags;
-		dev_dbg(&dev->sbd.core,
-			"%s:%u: bio %u: %u segs %u sectors from %lu\n",
-			__func__, __LINE__, i, bio_segments(iter.bio),
-			bio_sectors(iter.bio), iter.bio->bi_iter.bi_sector);
+		dev_dbg(&dev->sbd.core, "%s:%u: bio %u: %u sectors from %lu\n",
+			__func__, __LINE__, i, bio_sectors(iter.bio),
+			iter.bio->bi_iter.bi_sector);
 
 		size = bvec.bv_len;
 		buf = bvec_kmap_irq(&bvec, &flags);
diff --git a/drivers/md/bcache/io.c b/drivers/md/bcache/io.c
index 9b5b6a41a9b6..6e04f3bb0286 100644
--- a/drivers/md/bcache/io.c
+++ b/drivers/md/bcache/io.c
@@ -24,7 +24,8 @@ static void bch_generic_make_request_hack(struct bio *bio)
 	if (bio->bi_iter.bi_idx) {
 		struct bio_vec bv;
 		struct bvec_iter iter;
-		struct bio *clone = bio_alloc(GFP_NOIO, bio_segments(bio));
+		unsigned segs = bio_segments(bio);
+		struct bio *clone = bio_alloc(GFP_NOIO, segs);
 
 		bio_for_each_segment(bv, bio, iter)
 			clone->bi_io_vec[clone->bi_vcnt++] = bv;
@@ -32,7 +33,7 @@ static void bch_generic_make_request_hack(struct bio *bio)
 		clone->bi_iter.bi_sector = bio->bi_iter.bi_sector;
 		clone->bi_bdev		= bio->bi_bdev;
 		clone->bi_rw		= bio->bi_rw;
-		clone->bi_vcnt		= bio_segments(bio);
+		clone->bi_vcnt		= segs;
 		clone->bi_iter.bi_size	= bio->bi_iter.bi_size;
 
 		clone->bi_private	= bio;
@@ -133,40 +134,32 @@ out:
 
 static unsigned bch_bio_max_sectors(struct bio *bio)
 {
-	unsigned ret = bio_sectors(bio);
 	struct request_queue *q = bdev_get_queue(bio->bi_bdev);
-	unsigned max_segments = min_t(unsigned, BIO_MAX_PAGES,
-				      queue_max_segments(q));
+	struct bio_vec bv;
+	struct bvec_iter iter;
+	unsigned ret = 0, seg = 0;
 
 	if (bio->bi_rw & REQ_DISCARD)
-		return min(ret, q->limits.max_discard_sectors);
-
-	if (bio_segments(bio) > max_segments ||
-	    q->merge_bvec_fn) {
-		struct bio_vec bv;
-		struct bvec_iter iter;
-		unsigned seg = 0;
-
-		ret = 0;
+		return min(bio_sectors(bio), q->limits.max_discard_sectors);
 
-		bio_for_each_segment(bv, bio, iter) {
-			struct bvec_merge_data bvm = {
-				.bi_bdev	= bio->bi_bdev,
-				.bi_sector	= bio->bi_iter.bi_sector,
-				.bi_size	= ret << 9,
-				.bi_rw		= bio->bi_rw,
-			};
-
-			if (seg == max_segments)
-				break;
+	bio_for_each_segment(bv, bio, iter) {
+		struct bvec_merge_data bvm = {
+			.bi_bdev	= bio->bi_bdev,
+			.bi_sector	= bio->bi_iter.bi_sector,
+			.bi_size	= ret << 9,
+			.bi_rw		= bio->bi_rw,
+		};
+
+		if (seg == min_t(unsigned, BIO_MAX_PAGES,
+				 queue_max_segments(q)))
+			break;
 
-			if (q->merge_bvec_fn &&
-			    q->merge_bvec_fn(q, &bvm, &bv) < (int) bv.bv_len)
-				break;
+		if (q->merge_bvec_fn &&
+		    q->merge_bvec_fn(q, &bvm, &bv) < (int) bv.bv_len)
+			break;
 
-			seg++;
-			ret += bv.bv_len >> 9;
-		}
+		seg++;
+		ret += bv.bv_len >> 9;
 	}
 
 	ret = min(ret, queue_max_sectors(q));
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index e38d1d3226f3..8ee1a6c658b4 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -528,7 +528,7 @@ static void raid0_make_request(struct mddev *mddev, struct bio *bio)
 		sector_t sector = bio->bi_iter.bi_sector;
 		struct bio_pair *bp;
 		/* Sanity check -- queue functions should prevent this happening */
-		if (bio_segments(bio) > 1)
+		if (bio_multiple_segments(bio))
 			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 dbf3b63c2754..ac4bfa438c57 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1188,7 +1188,7 @@ 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_segments(bio) > 1)
+		if (bio_multiple_segments(bio))
 			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/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
index dd239bdbfcb4..00d339c361fc 100644
--- a/drivers/message/fusion/mptsas.c
+++ b/drivers/message/fusion/mptsas.c
@@ -2235,10 +2235,10 @@ static int mptsas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	}
 
 	/* do we need to support multiple segments? */
-	if (bio_segments(req->bio) > 1 || bio_segments(rsp->bio) > 1) {
-		printk(MYIOC_s_ERR_FMT "%s: multiple segments req %u %u, rsp %u %u\n",
-		    ioc->name, __func__, bio_segments(req->bio), blk_rq_bytes(req),
-		    bio_segments(rsp->bio), blk_rq_bytes(rsp));
+	if (bio_multiple_segments(req->bio) ||
+	    bio_multiple_segments(rsp->bio)) {
+		printk(MYIOC_s_ERR_FMT "%s: multiple segments req %u, rsp %u\n",
+		    ioc->name, __func__, blk_rq_bytes(req), blk_rq_bytes(rsp));
 		return -EINVAL;
 	}
 
diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 446b85110a1f..0cac7d8fd0f7 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -2163,10 +2163,10 @@ int sas_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	}
 
 	/* do we need to support multiple segments? */
-	if (bio_segments(req->bio) > 1 || bio_segments(rsp->bio) > 1) {
-		printk("%s: multiple segments req %u %u, rsp %u %u\n",
-		       __func__, bio_segments(req->bio), blk_rq_bytes(req),
-		       bio_segments(rsp->bio), blk_rq_bytes(rsp));
+	if (bio_multiple_segments(req->bio) ||
+	    bio_multiple_segments(rsp->bio)) {
+		printk("%s: multiple segments req %u, rsp %u\n",
+		       __func__, blk_rq_bytes(req), blk_rq_bytes(rsp));
 		return -EINVAL;
 	}
 
diff --git a/drivers/scsi/mpt2sas/mpt2sas_transport.c b/drivers/scsi/mpt2sas/mpt2sas_transport.c
index 7143e86af326..410f4a3e8888 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_transport.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_transport.c
@@ -1943,7 +1943,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	ioc->transport_cmds.status = MPT2_CMD_PENDING;
 
 	/* Check if the request is split across multiple segments */
-	if (bio_segments(req->bio) > 1) {
+	if (bio_multiple_segments(req->bio)) {
 		u32 offset = 0;
 
 		/* Allocate memory and copy the request */
@@ -1975,7 +1975,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 
 	/* Check if the response needs to be populated across
 	 * multiple segments */
-	if (bio_segments(rsp->bio) > 1) {
+	if (bio_multiple_segments(rsp->bio)) {
 		pci_addr_in = pci_alloc_consistent(ioc->pdev, blk_rq_bytes(rsp),
 		    &pci_dma_in);
 		if (!pci_addr_in) {
@@ -2042,7 +2042,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	sgl_flags = (MPI2_SGE_FLAGS_SIMPLE_ELEMENT |
 	    MPI2_SGE_FLAGS_END_OF_BUFFER | MPI2_SGE_FLAGS_HOST_TO_IOC);
 	sgl_flags = sgl_flags << MPI2_SGE_FLAGS_SHIFT;
-	if (bio_segments(req->bio) > 1) {
+	if (bio_multiple_segments(req->bio)) {
 		ioc->base_add_sg_single(psge, sgl_flags |
 		    (blk_rq_bytes(req) - 4), pci_dma_out);
 	} else {
@@ -2058,7 +2058,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	    MPI2_SGE_FLAGS_LAST_ELEMENT | MPI2_SGE_FLAGS_END_OF_BUFFER |
 	    MPI2_SGE_FLAGS_END_OF_LIST);
 	sgl_flags = sgl_flags << MPI2_SGE_FLAGS_SHIFT;
-	if (bio_segments(rsp->bio) > 1) {
+	if (bio_multiple_segments(rsp->bio)) {
 		ioc->base_add_sg_single(psge, sgl_flags |
 		    (blk_rq_bytes(rsp) + 4), pci_dma_in);
 	} else {
@@ -2103,7 +2103,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 		    le16_to_cpu(mpi_reply->ResponseDataLength);
 		/* check if the resp needs to be copied from the allocated
 		 * pci mem */
-		if (bio_segments(rsp->bio) > 1) {
+		if (bio_multiple_segments(rsp->bio)) {
 			u32 offset = 0;
 			u32 bytes_to_copy =
 			    le16_to_cpu(mpi_reply->ResponseDataLength);
diff --git a/drivers/scsi/mpt3sas/mpt3sas_transport.c b/drivers/scsi/mpt3sas/mpt3sas_transport.c
index 196a67f2e95f..65170cb1a00f 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_transport.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_transport.c
@@ -1926,7 +1926,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	ioc->transport_cmds.status = MPT3_CMD_PENDING;
 
 	/* Check if the request is split across multiple segments */
-	if (req->bio->bi_vcnt > 1) {
+	if (bio_multiple_segments(req->bio)) {
 		u32 offset = 0;
 
 		/* Allocate memory and copy the request */
@@ -1958,7 +1958,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 
 	/* Check if the response needs to be populated across
 	 * multiple segments */
-	if (rsp->bio->bi_vcnt > 1) {
+	if (bio_multiple_segments(rsp->bio)) {
 		pci_addr_in = pci_alloc_consistent(ioc->pdev, blk_rq_bytes(rsp),
 		    &pci_dma_in);
 		if (!pci_addr_in) {
@@ -2019,7 +2019,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 	mpi_request->RequestDataLength = cpu_to_le16(blk_rq_bytes(req) - 4);
 	psge = &mpi_request->SGL;
 
-	if (req->bio->bi_vcnt > 1)
+	if (bio_multiple_segments(req->bio))
 		ioc->build_sg(ioc, psge, pci_dma_out, (blk_rq_bytes(req) - 4),
 		    pci_dma_in, (blk_rq_bytes(rsp) + 4));
 	else
@@ -2064,7 +2064,7 @@ _transport_smp_handler(struct Scsi_Host *shost, struct sas_rphy *rphy,
 
 		/* check if the resp needs to be copied from the allocated
 		 * pci mem */
-		if (rsp->bio->bi_vcnt > 1) {
+		if (bio_multiple_segments(rsp->bio)) {
 			u32 offset = 0;
 			u32 bytes_to_copy =
 			    le16_to_cpu(mpi_reply->ResponseDataLength);