block: add a BIO_MAX_SIZE constant and use it

Currently the only constant for the maximum bio size is BIO_MAX_SECTORS,
which is in units of 512-byte sectors, but a lot of user need a byte
limit.

Add a BIO_MAX_SIZE constant, redefine BIO_MAX_SECTORS in terms of it, and
switch all bio-related uses of UINT_MAX for the maximum size to use the
symbolic names instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 4 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index b82c6d304658..0eb0aef97197 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -95,13 +95,13 @@ static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
 }
 
 /*
- * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
- * is defined as 'unsigned int', meantime it has to be aligned to with the
+ * The maximum size that a bio can fit has to be aligned down to the
  * logical block size, which is the minimum accepted unit by hardware.
  */
 static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
 {
-	return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
+	return round_down(BIO_MAX_SIZE, lim->logical_block_size) >>
+			SECTOR_SHIFT;
 }
 
 /*
@@ -502,7 +502,7 @@ unsigned int blk_recalc_rq_segments(struct request *rq)
 
 	rq_for_each_bvec(bv, rq, iter)
 		bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
-				UINT_MAX, UINT_MAX);
+				UINT_MAX, BIO_MAX_SIZE);
 	return nr_phys_segs;
 }