Merge tag 'md-fixes-20230630' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into block-6.5

Pull MD fix from Song:

"This patch fixes data corruption caused by discard on raid0 array with
 original layout."

* tag 'md-fixes-20230630' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md/raid0: add discard support for the 'original' layout

2 files changed, 55 insertions, 8 deletions

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index f8ee9a95e25d5d..d1ac73fcd85292 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -270,6 +270,18 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
 		goto abort;
 	}
 
+	if (conf->layout == RAID0_ORIG_LAYOUT) {
+		for (i = 1; i < conf->nr_strip_zones; i++) {
+			sector_t first_sector = conf->strip_zone[i-1].zone_end;
+
+			sector_div(first_sector, mddev->chunk_sectors);
+			zone = conf->strip_zone + i;
+			/* disk_shift is first disk index used in the zone */
+			zone->disk_shift = sector_div(first_sector,
+						      zone->nb_dev);
+		}
+	}
+
 	pr_debug("md/raid0:%s: done.\n", mdname(mddev));
 	*private_conf = conf;
 
@@ -431,6 +443,20 @@ exit_acct_set:
 	return ret;
 }
 
+/*
+ * Convert disk_index to the disk order in which it is read/written.
+ *  For example, if we have 4 disks, they are numbered 0,1,2,3. If we
+ *  write the disks starting at disk 3, then the read/write order would
+ *  be disk 3, then 0, then 1, and then disk 2 and we want map_disk_shift()
+ *  to map the disks as follows 0,1,2,3 => 1,2,3,0. So disk 0 would map
+ *  to 1, 1 to 2, 2 to 3, and 3 to 0. That way we can compare disks in
+ *  that 'output' space to understand the read/write disk ordering.
+ */
+static int map_disk_shift(int disk_index, int num_disks, int disk_shift)
+{
+	return ((disk_index + num_disks - disk_shift) % num_disks);
+}
+
 static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 {
 	struct r0conf *conf = mddev->private;
@@ -444,7 +470,9 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 	sector_t end_disk_offset;
 	unsigned int end_disk_index;
 	unsigned int disk;
+	sector_t orig_start, orig_end;
 
+	orig_start = start;
 	zone = find_zone(conf, &start);
 
 	if (bio_end_sector(bio) > zone->zone_end) {
@@ -458,6 +486,7 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 	} else
 		end = bio_end_sector(bio);
 
+	orig_end = end;
 	if (zone != conf->strip_zone)
 		end = end - zone[-1].zone_end;
 
@@ -469,13 +498,26 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 	last_stripe_index = end;
 	sector_div(last_stripe_index, stripe_size);
 
-	start_disk_index = (int)(start - first_stripe_index * stripe_size) /
-		mddev->chunk_sectors;
+	/* In the first zone the original and alternate layouts are the same */
+	if ((conf->layout == RAID0_ORIG_LAYOUT) && (zone != conf->strip_zone)) {
+		sector_div(orig_start, mddev->chunk_sectors);
+		start_disk_index = sector_div(orig_start, zone->nb_dev);
+		start_disk_index = map_disk_shift(start_disk_index,
+						  zone->nb_dev,
+						  zone->disk_shift);
+		sector_div(orig_end, mddev->chunk_sectors);
+		end_disk_index = sector_div(orig_end, zone->nb_dev);
+		end_disk_index = map_disk_shift(end_disk_index,
+						zone->nb_dev, zone->disk_shift);
+	} else {
+		start_disk_index = (int)(start - first_stripe_index * stripe_size) /
+			mddev->chunk_sectors;
+		end_disk_index = (int)(end - last_stripe_index * stripe_size) /
+			mddev->chunk_sectors;
+	}
 	start_disk_offset = ((int)(start - first_stripe_index * stripe_size) %
 		mddev->chunk_sectors) +
 		first_stripe_index * mddev->chunk_sectors;
-	end_disk_index = (int)(end - last_stripe_index * stripe_size) /
-		mddev->chunk_sectors;
 	end_disk_offset = ((int)(end - last_stripe_index * stripe_size) %
 		mddev->chunk_sectors) +
 		last_stripe_index * mddev->chunk_sectors;
@@ -483,18 +525,22 @@ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
 	for (disk = 0; disk < zone->nb_dev; disk++) {
 		sector_t dev_start, dev_end;
 		struct md_rdev *rdev;
+		int compare_disk;
+
+		compare_disk = map_disk_shift(disk, zone->nb_dev,
+					      zone->disk_shift);
 
-		if (disk < start_disk_index)
+		if (compare_disk < start_disk_index)
 			dev_start = (first_stripe_index + 1) *
 				mddev->chunk_sectors;
-		else if (disk > start_disk_index)
+		else if (compare_disk > start_disk_index)
 			dev_start = first_stripe_index * mddev->chunk_sectors;
 		else
 			dev_start = start_disk_offset;
 
-		if (disk < end_disk_index)
+		if (compare_disk < end_disk_index)
 			dev_end = (last_stripe_index + 1) * mddev->chunk_sectors;
-		else if (disk > end_disk_index)
+		else if (compare_disk > end_disk_index)
 			dev_end = last_stripe_index * mddev->chunk_sectors;
 		else
 			dev_end = end_disk_offset;
diff --git a/drivers/md/raid0.h b/drivers/md/raid0.h
index 3816e5477db1e7..8cc761ca742300 100644
--- a/drivers/md/raid0.h
+++ b/drivers/md/raid0.h
@@ -6,6 +6,7 @@ struct strip_zone {
 	sector_t zone_end;	/* Start of the next zone (in sectors) */
 	sector_t dev_start;	/* Zone offset in real dev (in sectors) */
 	int	 nb_dev;	/* # of devices attached to the zone */
+	int	 disk_shift;	/* start disk for the original layout */
 };
 
 /* Linux 3.14 (20d0189b101) made an unintended change to