[PATCH] dm dust: use target-relative sectors in badblock messages

dm-dust stores bad blocks in target-relative sectors, but some messages
report or compare values in a different coordinate space. A table with a
non-zero target offset can therefore describe one sector while reporting
another.

This makes diagnostics misleading and can make scripted validation look
at the wrong logical block.

Keep the badblock control path in target-relative coordinates when
reporting and matching stored bad blocks.

Assisted-by: Codex:gpt-5.5-cyber-preview
Signed-off-by: Samuel Moelius <[email protected]>
---
 drivers/md/dm-dust.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm-dust.c b/drivers/md/dm-dust.c
index c7e3077fb1f5..45d4154209b7 100644
--- a/drivers/md/dm-dust.c
+++ b/drivers/md/dm-dust.c
@@ -224,15 +224,16 @@ static int dust_map_write(struct dust_device *dd, sector_t thisblock,
 static int dust_map(struct dm_target *ti, struct bio *bio)
 {
 	struct dust_device *dd = ti->private;
+	sector_t dust_sector = dm_target_offset(ti, bio->bi_iter.bi_sector);
 	int r;
 
 	bio_set_dev(bio, dd->dev->bdev);
-	bio->bi_iter.bi_sector = dd->start + dm_target_offset(ti, bio->bi_iter.bi_sector);
+	bio->bi_iter.bi_sector = dd->start + dust_sector;
 
 	if (bio_data_dir(bio) == READ)
-		r = dust_map_read(dd, bio->bi_iter.bi_sector, dd->fail_read_on_bb);
+		r = dust_map_read(dd, dust_sector, dd->fail_read_on_bb);
 	else
-		r = dust_map_write(dd, bio->bi_iter.bi_sector, dd->fail_read_on_bb);
+		r = dust_map_write(dd, dust_sector, dd->fail_read_on_bb);
 
 	return r;
 }
@@ -415,7 +416,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
 			char *result, unsigned int maxlen)
 {
 	struct dust_device *dd = ti->private;
-	sector_t size = bdev_nr_sectors(dd->dev->bdev);
+	sector_t size = dm_sector_div_up(ti->len, dd->sect_per_block);
 	bool invalid_msg = false;
 	int r = -EINVAL;
 	unsigned long long tmp, block;
@@ -462,8 +463,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
 			return r;
 
 		block = tmp;
-		sector_div(size, dd->sect_per_block);
-		if (block > size) {
+		if (block >= size) {
 			DMERR("selected block value out of range");
 			return r;
 		}
@@ -490,8 +490,7 @@ static int dust_message(struct dm_target *ti, unsigned int argc, char **argv,
 			return r;
 		}
 		wr_fail_cnt = tmp_ui;
-		sector_div(size, dd->sect_per_block);
-		if (block > size) {
+		if (block >= size) {
 			DMERR("selected block value out of range");
 			return r;
 		}
-- 
2.43.0