add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/block/blk-lib.c
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@@ -10,8 +10,7 @@
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 #include "blk.h"
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-static struct bio *next_bio(struct bio *bio, unsigned int nr_pages,
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-		gfp_t gfp)
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+struct bio *blk_next_bio(struct bio *bio, unsigned int nr_pages, gfp_t gfp)
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 {
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 	struct bio *new = bio_alloc(gfp, nr_pages);
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@@ -30,7 +29,7 @@
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 	struct request_queue *q = bdev_get_queue(bdev);
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 	struct bio *bio = *biop;
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 	unsigned int op;
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-	sector_t bs_mask;
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+	sector_t bs_mask, part_offset = 0;
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 	if (!q)
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 		return -ENXIO;
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@@ -48,6 +47,15 @@
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 		op = REQ_OP_DISCARD;
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 	}
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+	/* In case the discard granularity isn't set by buggy device driver */
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+	if (WARN_ON_ONCE(!q->limits.discard_granularity)) {
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+		char dev_name[BDEVNAME_SIZE];
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+
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+		bdevname(bdev, dev_name);
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+		pr_err_ratelimited("%s: Error: discard_granularity is 0.\n", dev_name);
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+		return -EOPNOTSUPP;
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+	}
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+
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 	bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1;
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 	if ((sector | nr_sects) & bs_mask)
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 		return -EINVAL;
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@@ -55,13 +63,38 @@
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 	if (!nr_sects)
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 		return -EINVAL;
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+	/* In case the discard request is in a partition */
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+	if (bdev_is_partition(bdev))
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+		part_offset = bdev->bd_part->start_sect;
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+
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 	while (nr_sects) {
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-		sector_t req_sects = min_t(sector_t, nr_sects,
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-				bio_allowed_max_sectors(q));
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+		sector_t granularity_aligned_lba, req_sects;
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+		sector_t sector_mapped = sector + part_offset;
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+
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+		granularity_aligned_lba = round_up(sector_mapped,
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+				q->limits.discard_granularity >> SECTOR_SHIFT);
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+
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+		/*
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+		 * Check whether the discard bio starts at a discard_granularity
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+		 * aligned LBA,
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+		 * - If no: set (granularity_aligned_lba - sector_mapped) to
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+		 *   bi_size of the first split bio, then the second bio will
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+		 *   start at a discard_granularity aligned LBA on the device.
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+		 * - If yes: use bio_aligned_discard_max_sectors() as the max
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+		 *   possible bi_size of the first split bio. Then when this bio
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+		 *   is split in device drive, the split ones are very probably
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+		 *   to be aligned to discard_granularity of the device's queue.
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+		 */
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+		if (granularity_aligned_lba == sector_mapped)
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+			req_sects = min_t(sector_t, nr_sects,
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+					  bio_aligned_discard_max_sectors(q));
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+		else
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+			req_sects = min_t(sector_t, nr_sects,
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+					  granularity_aligned_lba - sector_mapped);
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 		WARN_ON_ONCE((req_sects << 9) > UINT_MAX);
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-		bio = next_bio(bio, 0, gfp_mask);
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+		bio = blk_next_bio(bio, 0, gfp_mask);
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 		bio->bi_iter.bi_sector = sector;
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 		bio_set_dev(bio, bdev);
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 		bio_set_op_attrs(bio, op, 0);
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@@ -155,7 +188,7 @@
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 	max_write_same_sectors = bio_allowed_max_sectors(q);
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 	while (nr_sects) {
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-		bio = next_bio(bio, 1, gfp_mask);
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+		bio = blk_next_bio(bio, 1, gfp_mask);
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 		bio->bi_iter.bi_sector = sector;
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 		bio_set_dev(bio, bdev);
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 		bio->bi_vcnt = 1;
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@@ -231,7 +264,7 @@
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 		return -EOPNOTSUPP;
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 	while (nr_sects) {
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-		bio = next_bio(bio, 0, gfp_mask);
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+		bio = blk_next_bio(bio, 0, gfp_mask);
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 		bio->bi_iter.bi_sector = sector;
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 		bio_set_dev(bio, bdev);
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 		bio->bi_opf = REQ_OP_WRITE_ZEROES;
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@@ -282,8 +315,8 @@
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 		return -EPERM;
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 	while (nr_sects != 0) {
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-		bio = next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
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-			       gfp_mask);
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+		bio = blk_next_bio(bio, __blkdev_sectors_to_bio_pages(nr_sects),
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+				   gfp_mask);
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 		bio->bi_iter.bi_sector = sector;
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 		bio_set_dev(bio, bdev);
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 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);