[PATCH 1/8] md: change chunk_sectors and stripe cache counts to unsigned int

[Hiroshi Nishida]

chunk_sectors, new_chunk_sectors, prev_chunk_sectors, max_nr_stripes,
and min_nr_stripes are never negative. Using signed int is semantically
wrong and prevents the compiler from optimizing division/modulo by
power-of-two chunk sizes to right shifts in the hot I/O path.

Change all struct fields and derived local variables to unsigned int:
  mddev->chunk_sectors
  mddev->new_chunk_sectors
  r5conf->chunk_sectors
  r5conf->prev_chunk_sectors
  r5conf->max_nr_stripes
  r5conf->min_nr_stripes
  Local: sectors_per_chunk, new_chunk, chunk_sectors

The min() in r5c_check_cached_full_stripe() required both operands to
match signedness; this is now satisfied with max_nr_stripes unsigned.

Assisted-by: Claude:claude-opus-4-8 [Claude Code]
Signed-off-by: Hiroshi Nishida <nishidafmly@xxxxxxxxx>
---
 drivers/md/md.h    |  4 ++--
 drivers/md/raid5.c | 14 +++++++-------
 drivers/md/raid5.h |  8 ++++----
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/md/md.h b/drivers/md/md.h
index d8daf0f75cbb..b9ad26844799 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -437,7 +437,7 @@ struct mddev {
 	int				external;	/* metadata is
 							 * managed externally */
 	char				metadata_type[17]; /* externally set*/
-	int				chunk_sectors;
+	unsigned int			chunk_sectors;
 	time64_t			ctime, utime;
 	int				level, layout;
 	char				clevel[16];
@@ -466,7 +466,7 @@ struct mddev {
 	 */
 	sector_t			reshape_position;
 	int				delta_disks, new_level, new_layout;
-	int				new_chunk_sectors;
+	unsigned int			new_chunk_sectors;
 	int				reshape_backwards;
 
 	struct md_thread __rcu		*thread;	/* management thread */
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 0c5c9fb0606e..28828e083c2b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2970,7 +2970,7 @@ sector_t raid5_compute_sector(struct r5conf *conf, sector_t r_sector,
 	sector_t new_sector;
 	int algorithm = previous ? conf->prev_algo
 				 : conf->algorithm;
-	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
+	unsigned int sectors_per_chunk = previous ? conf->prev_chunk_sectors
 					 : conf->chunk_sectors;
 	int raid_disks = previous ? conf->previous_raid_disks
 				  : conf->raid_disks;
@@ -3166,7 +3166,7 @@ sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous)
 	int raid_disks = sh->disks;
 	int data_disks = raid_disks - conf->max_degraded;
 	sector_t new_sector = sh->sector, check;
-	int sectors_per_chunk = previous ? conf->prev_chunk_sectors
+	unsigned int sectors_per_chunk = previous ? conf->prev_chunk_sectors
 					 : conf->chunk_sectors;
 	int algorithm = previous ? conf->prev_algo
 				 : conf->algorithm;
@@ -3584,7 +3584,7 @@ static void end_reshape(struct r5conf *conf);
 static void stripe_set_idx(sector_t stripe, struct r5conf *conf, int previous,
 			    struct stripe_head *sh)
 {
-	int sectors_per_chunk =
+	unsigned int sectors_per_chunk =
 		previous ? conf->prev_chunk_sectors : conf->chunk_sectors;
 	int dd_idx;
 	int chunk_offset = sector_div(stripe, sectors_per_chunk);
@@ -6103,7 +6103,7 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
 static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
 					      struct bio *bi)
 {
-	int sectors_per_chunk = conf->chunk_sectors;
+	unsigned int sectors_per_chunk = conf->chunk_sectors;
 	int raid_disks = conf->raid_disks;
 	int dd_idx;
 	struct stripe_head sh;
@@ -7930,7 +7930,7 @@ static int raid5_run(struct mddev *mddev)
 		sector_t here_new, here_old;
 		int old_disks;
 		int max_degraded = (mddev->level == 6 ? 2 : 1);
-		int chunk_sectors;
+		unsigned int chunk_sectors;
 		int new_data_disks;
 
 		if (journal_dev) {
@@ -8832,7 +8832,7 @@ static int raid5_check_reshape(struct mddev *mddev)
 	 * to be used by a reshape pass.
 	 */
 	struct r5conf *conf = mddev->private;
-	int new_chunk = mddev->new_chunk_sectors;
+	unsigned int new_chunk = mddev->new_chunk_sectors;
 
 	if (mddev->new_layout >= 0 && !algorithm_valid_raid5(mddev->new_layout))
 		return -EINVAL;
@@ -8866,7 +8866,7 @@ static int raid5_check_reshape(struct mddev *mddev)
 
 static int raid6_check_reshape(struct mddev *mddev)
 {
-	int new_chunk = mddev->new_chunk_sectors;
+	unsigned int new_chunk = mddev->new_chunk_sectors;
 
 	if (mddev->new_layout >= 0 && !algorithm_valid_raid6(mddev->new_layout))
 		return -EINVAL;
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index cb5feae04db2..5cd9d0f36b6e 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -572,12 +572,12 @@ struct r5conf {
 	/* only protect corresponding hash list and inactive_list */
 	spinlock_t		hash_locks[NR_STRIPE_HASH_LOCKS];
 	struct mddev		*mddev;
-	int			chunk_sectors;
+	unsigned int		chunk_sectors;
 	int			level, algorithm, rmw_level;
 	int			max_degraded;
 	int			raid_disks;
-	int			max_nr_stripes;
-	int			min_nr_stripes;
+	unsigned int		max_nr_stripes;
+	unsigned int		min_nr_stripes;
 #if PAGE_SIZE != DEFAULT_STRIPE_SIZE
 	unsigned long	stripe_size;
 	unsigned int	stripe_shift;
@@ -595,7 +595,7 @@ struct r5conf {
 	 */
 	sector_t		reshape_safe;
 	int			previous_raid_disks;
-	int			prev_chunk_sectors;
+	unsigned int		prev_chunk_sectors;
 	int			prev_algo;
 	short			generation; /* increments with every reshape */
 	seqcount_spinlock_t	gen_lock;	/* lock against generation changes */
-- 
2.43.0