block: Add bio_max_segs

It's often inconvenient to use BIO_MAX_PAGES due to min() requiring the
sign to be the same.  Introduce bio_max_segs() and change BIO_MAX_PAGES to
be unsigned to make it easier for the users.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

7 files changed, 18 insertions, 23 deletions

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index da16121140ca..1cdf09ff67b6 100644
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1326,9 +1326,7 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 				     pages[i]->page,
 				     seg[i].nsec << 9,
 				     seg[i].offset) == 0)) {
-
-			int nr_iovecs = min_t(int, (nseg-i), BIO_MAX_PAGES);
-			bio = bio_alloc(GFP_KERNEL, nr_iovecs);
+			bio = bio_alloc(GFP_KERNEL, bio_max_segs(nseg - i));
 			if (unlikely(bio == NULL))
 				goto fail_put_bio;
 
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index 4312007d2d34..2d3cda0acacb 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -341,8 +341,8 @@ static void do_region(int op, int op_flags, unsigned region,
 			num_bvecs = 1;
 			break;
 		default:
-			num_bvecs = min_t(int, BIO_MAX_PAGES,
-					  dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
+			num_bvecs = bio_max_segs(dm_sector_div_up(remaining,
+						(PAGE_SIZE >> SECTOR_SHIFT)));
 		}
 
 		bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, &io->client->bios);
diff --git a/drivers/md/dm-log-writes.c b/drivers/md/dm-log-writes.c
index e3d35c6c9f71..57882654ffee 100644
--- a/drivers/md/dm-log-writes.c
+++ b/drivers/md/dm-log-writes.c
@@ -264,15 +264,14 @@ static int write_inline_data(struct log_writes_c *lc, void *entry,
 			     size_t entrylen, void *data, size_t datalen,
 			     sector_t sector)
 {
-	int num_pages, bio_pages, pg_datalen, pg_sectorlen, i;
+	int bio_pages, pg_datalen, pg_sectorlen, i;
 	struct page *page;
 	struct bio *bio;
 	size_t ret;
 	void *ptr;
 
 	while (datalen) {
-		num_pages = ALIGN(datalen, PAGE_SIZE) >> PAGE_SHIFT;
-		bio_pages = min(num_pages, BIO_MAX_PAGES);
+		bio_pages = bio_max_segs(DIV_ROUND_UP(datalen, PAGE_SIZE));
 
 		atomic_inc(&lc->io_blocks);
 
@@ -364,7 +363,7 @@ static int log_one_block(struct log_writes_c *lc,
 		goto out;
 
 	atomic_inc(&lc->io_blocks);
-	bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES));
+	bio = bio_alloc(GFP_KERNEL, bio_max_segs(block->vec_cnt));
 	if (!bio) {
 		DMERR("Couldn't alloc log bio");
 		goto error;
@@ -386,7 +385,8 @@ static int log_one_block(struct log_writes_c *lc,
 		if (ret != block->vecs[i].bv_len) {
 			atomic_inc(&lc->io_blocks);
 			submit_bio(bio);
-			bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES));
+			bio = bio_alloc(GFP_KERNEL,
+					bio_max_segs(block->vec_cnt - i));
 			if (!bio) {
 				DMERR("Couldn't alloc log bio");
 				goto error;
diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 3d9a5d3ed9cd..9a8b3726a37c 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -185,7 +185,7 @@ static int nvmet_bdev_alloc_bip(struct nvmet_req *req, struct bio *bio,
 	}
 
 	bip = bio_integrity_alloc(bio, GFP_NOIO,
-		min_t(unsigned int, req->metadata_sg_cnt, BIO_MAX_PAGES));
+					bio_max_segs(req->metadata_sg_cnt));
 	if (IS_ERR(bip)) {
 		pr_err("Unable to allocate bio_integrity_payload\n");
 		return PTR_ERR(bip);
@@ -225,7 +225,7 @@ static int nvmet_bdev_alloc_bip(struct nvmet_req *req, struct bio *bio,
 
 static void nvmet_bdev_execute_rw(struct nvmet_req *req)
 {
-	int sg_cnt = req->sg_cnt;
+	unsigned int sg_cnt = req->sg_cnt;
 	struct bio *bio;
 	struct scatterlist *sg;
 	struct blk_plug plug;
@@ -262,7 +262,7 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
 		bio = &req->b.inline_bio;
 		bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
 	} else {
-		bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
+		bio = bio_alloc(GFP_KERNEL, bio_max_segs(sg_cnt));
 	}
 	bio_set_dev(bio, req->ns->bdev);
 	bio->bi_iter.bi_sector = sector;
@@ -289,7 +289,7 @@ static void nvmet_bdev_execute_rw(struct nvmet_req *req)
 				}
 			}
 
-			bio = bio_alloc(GFP_KERNEL, min(sg_cnt, BIO_MAX_PAGES));
+			bio = bio_alloc(GFP_KERNEL, bio_max_segs(sg_cnt));
 			bio_set_dev(bio, req->ns->bdev);
 			bio->bi_iter.bi_sector = sector;
 			bio->bi_opf = op;
diff --git a/drivers/nvme/target/passthru.c b/drivers/nvme/target/passthru.c
index f50c7b2bf21c..26c587ccd152 100644
--- a/drivers/nvme/target/passthru.c
+++ b/drivers/nvme/target/passthru.c
@@ -26,7 +26,7 @@ static u16 nvmet_passthru_override_id_ctrl(struct nvmet_req *req)
 	struct nvme_ctrl *pctrl = ctrl->subsys->passthru_ctrl;
 	u16 status = NVME_SC_SUCCESS;
 	struct nvme_id_ctrl *id;
-	int max_hw_sectors;
+	unsigned int max_hw_sectors;
 	int page_shift;
 
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
@@ -198,7 +198,7 @@ static int nvmet_passthru_map_sg(struct nvmet_req *req, struct request *rq)
 		bio = &req->p.inline_bio;
 		bio_init(bio, req->inline_bvec, ARRAY_SIZE(req->inline_bvec));
 	} else {
-		bio = bio_alloc(GFP_KERNEL, min(req->sg_cnt, BIO_MAX_PAGES));
+		bio = bio_alloc(GFP_KERNEL, bio_max_segs(req->sg_cnt));
 		bio->bi_end_io = bio_put;
 	}
 	bio->bi_opf = req_op(rq);
diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index 8ed93fd205c7..ee3d52061281 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -315,10 +315,8 @@ iblock_get_bio(struct se_cmd *cmd, sector_t lba, u32 sg_num, int op,
 	 * Only allocate as many vector entries as the bio code allows us to,
 	 * we'll loop later on until we have handled the whole request.
 	 */
-	if (sg_num > BIO_MAX_PAGES)
-		sg_num = BIO_MAX_PAGES;
-
-	bio = bio_alloc_bioset(GFP_NOIO, sg_num, &ib_dev->ibd_bio_set);
+	bio = bio_alloc_bioset(GFP_NOIO, bio_max_segs(sg_num),
+				&ib_dev->ibd_bio_set);
 	if (!bio) {
 		pr_err("Unable to allocate memory for bio\n");
 		return NULL;
@@ -638,8 +636,7 @@ iblock_alloc_bip(struct se_cmd *cmd, struct bio *bio,
 		return -ENODEV;
 	}
 
-	bip = bio_integrity_alloc(bio, GFP_NOIO,
-			min_t(unsigned int, cmd->t_prot_nents, BIO_MAX_PAGES));
+	bip = bio_integrity_alloc(bio, GFP_NOIO, bio_max_segs(cmd->t_prot_nents));
 	if (IS_ERR(bip)) {
 		pr_err("Unable to allocate bio_integrity_payload\n");
 		return PTR_ERR(bip);
diff --git a/drivers/target/target_core_pscsi.c b/drivers/target/target_core_pscsi.c
index 33770e5808ce..3cbc074992bc 100644
--- a/drivers/target/target_core_pscsi.c
+++ b/drivers/target/target_core_pscsi.c
@@ -881,7 +881,7 @@ pscsi_map_sg(struct se_cmd *cmd, struct scatterlist *sgl, u32 sgl_nents,
 
 			if (!bio) {
 new_bio:
-				nr_vecs = min_t(int, BIO_MAX_PAGES, nr_pages);
+				nr_vecs = bio_max_segs(nr_pages);
 				nr_pages -= nr_vecs;
 				/*
 				 * Calls bio_kmalloc() and sets bio->bi_end_io()