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>

4 files changed, 15 insertions, 15 deletions

diff --git a/block/bio.c b/block/bio.c
index 2359c0723b88..ac7703e149c6 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -924,7 +924,7 @@ static inline bool bio_full(struct bio *bio, unsigned len)
 {
 	if (bio->bi_vcnt >= bio->bi_max_vecs)
 		return true;
-	if (bio->bi_iter.bi_size > UINT_MAX - len)
+	if (bio->bi_iter.bi_size > BIO_MAX_SIZE - len)
 		return true;
 	return false;
 }
@@ -1030,7 +1030,7 @@ int bio_add_page(struct bio *bio, struct page *page,
 {
 	if (WARN_ON_ONCE(bio_flagged(bio, BIO_CLONED)))
 		return 0;
-	if (bio->bi_iter.bi_size > UINT_MAX - len)
+	if (bio->bi_iter.bi_size > BIO_MAX_SIZE - len)
 		return 0;
 
 	if (bio->bi_vcnt > 0) {
@@ -1057,7 +1057,7 @@ void bio_add_folio_nofail(struct bio *bio, struct folio *folio, size_t len,
 {
 	unsigned long nr = off / PAGE_SIZE;
 
-	WARN_ON_ONCE(len > UINT_MAX);
+	WARN_ON_ONCE(len > BIO_MAX_SIZE);
 	__bio_add_page(bio, folio_page(folio, nr), len, off % PAGE_SIZE);
 }
 EXPORT_SYMBOL_GPL(bio_add_folio_nofail);
@@ -1081,7 +1081,7 @@ bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
 {
 	unsigned long nr = off / PAGE_SIZE;
 
-	if (len > UINT_MAX)
+	if (len > BIO_MAX_SIZE)
 		return false;
 	return bio_add_page(bio, folio_page(folio, nr), len, off % PAGE_SIZE) > 0;
 }
@@ -1238,7 +1238,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 		extraction_flags |= ITER_ALLOW_P2PDMA;
 
 	size = iov_iter_extract_pages(iter, &pages,
-				      UINT_MAX - bio->bi_iter.bi_size,
+				      BIO_MAX_SIZE - bio->bi_iter.bi_size,
 				      nr_pages, extraction_flags, &offset);
 	if (unlikely(size <= 0))
 		return size ? size : -EFAULT;
diff --git a/block/blk-lib.c b/block/blk-lib.c
index 9e2cc58f881f..0be3acdc3eb5 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -32,7 +32,7 @@ static sector_t bio_discard_limit(struct block_device *bdev, sector_t sector)
 	 * Align the bio size to the discard granularity to make splitting the bio
 	 * at discard granularity boundaries easier in the driver if needed.
 	 */
-	return round_down(UINT_MAX, discard_granularity) >> SECTOR_SHIFT;
+	return round_down(BIO_MAX_SIZE, discard_granularity) >> SECTOR_SHIFT;
 }
 
 struct bio *blk_alloc_discard_bio(struct block_device *bdev,
@@ -107,8 +107,7 @@ static sector_t bio_write_zeroes_limit(struct block_device *bdev)
 {
 	sector_t bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
 
-	return min(bdev_write_zeroes_sectors(bdev),
-		(UINT_MAX >> SECTOR_SHIFT) & ~bs_mask);
+	return min(bdev_write_zeroes_sectors(bdev), BIO_MAX_SECTORS & ~bs_mask);
 }
 
 /*
@@ -337,8 +336,8 @@ int blkdev_issue_secure_erase(struct block_device *bdev, sector_t sector,
 	int ret = 0;
 
 	/* make sure that "len << SECTOR_SHIFT" doesn't overflow */
-	if (max_sectors > UINT_MAX >> SECTOR_SHIFT)
-		max_sectors = UINT_MAX >> SECTOR_SHIFT;
+	if (max_sectors > BIO_MAX_SECTORS)
+		max_sectors = BIO_MAX_SECTORS;
 	max_sectors &= ~bs_mask;
 
 	if (max_sectors == 0)
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;
 }
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 19a888a2f104..d59553324a84 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -281,7 +281,8 @@ struct bio {
 };
 
 #define BIO_RESET_BYTES		offsetof(struct bio, bi_max_vecs)
-#define BIO_MAX_SECTORS		(UINT_MAX >> SECTOR_SHIFT)
+#define BIO_MAX_SIZE		UINT_MAX /* max value of bi_iter.bi_size */
+#define BIO_MAX_SECTORS		(BIO_MAX_SIZE >> SECTOR_SHIFT)
 
 static inline struct bio_vec *bio_inline_vecs(struct bio *bio)
 {