Merge tag 'md-next-2023-04-28' of...

Merge tag 'md-next-2023-04-28' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-6.4/block

Pull MD fixes from Song:

"1. Improve raid5 sequential IO performance on spinning disks, which fixes
    a regression since v6.0, by Jan Kara.
 2. Fix bitmap offset types, which fixes an issue introduced in this merge
    window, by Jonathan Derrick."

* tag 'md-next-2023-04-28' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: Fix bitmap offset type in sb writer
  md/raid5: Improve performance for sequential IO

drivers/md/md-bitmap.c

@@ -219,7 +219,7 @@ static unsigned int optimal_io_size(struct block_device *bdev,
 }
 
 static unsigned int bitmap_io_size(unsigned int io_size, unsigned int opt_size,
-				   sector_t start, sector_t boundary)
+				   loff_t start, loff_t boundary)
 {
 	if (io_size != opt_size &&
 	    start + opt_size / SECTOR_SIZE <= boundary)
@@ -237,8 +237,8 @@ static int __write_sb_page(struct md_rdev *rdev, struct bitmap *bitmap,
 	struct block_device *bdev;
 	struct mddev *mddev = bitmap->mddev;
 	struct bitmap_storage *store = &bitmap->storage;
-	sector_t offset = mddev->bitmap_info.offset;
-	sector_t ps, sboff, doff;
+	loff_t sboff, offset = mddev->bitmap_info.offset;
+	sector_t ps, doff;
 	unsigned int size = PAGE_SIZE;
 	unsigned int opt_size = PAGE_SIZE;
 

drivers/md/raid5.c

@@ -6079,6 +6079,38 @@ static enum stripe_result make_stripe_request(struct mddev *mddev,
 	return ret;
 }
 
+/*
+ * If the bio covers multiple data disks, find sector within the bio that has
+ * the lowest chunk offset in the first chunk.
+ */
+static sector_t raid5_bio_lowest_chunk_sector(struct r5conf *conf,
+					      struct bio *bi)
+{
+	int sectors_per_chunk = conf->chunk_sectors;
+	int raid_disks = conf->raid_disks;
+	int dd_idx;
+	struct stripe_head sh;
+	unsigned int chunk_offset;
+	sector_t r_sector = bi->bi_iter.bi_sector & ~((sector_t)RAID5_STRIPE_SECTORS(conf)-1);
+	sector_t sector;
+
+	/* We pass in fake stripe_head to get back parity disk numbers */
+	sector = raid5_compute_sector(conf, r_sector, 0, &dd_idx, &sh);
+	chunk_offset = sector_div(sector, sectors_per_chunk);
+	if (sectors_per_chunk - chunk_offset >= bio_sectors(bi))
+		return r_sector;
+	/*
+	 * Bio crosses to the next data disk. Check whether it's in the same
+	 * chunk.
+	 */
+	dd_idx++;
+	while (dd_idx == sh.pd_idx || dd_idx == sh.qd_idx)
+		dd_idx++;
+	if (dd_idx >= raid_disks)
+		return r_sector;
+	return r_sector + sectors_per_chunk - chunk_offset;
+}
+
 static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 {
 	DEFINE_WAIT_FUNC(wait, woken_wake_function);
@@ -6150,6 +6182,17 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 	}
 	md_account_bio(mddev, &bi);
 
+	/*
+	 * Lets start with the stripe with the lowest chunk offset in the first
+	 * chunk. That has the best chances of creating IOs adjacent to
+	 * previous IOs in case of sequential IO and thus creates the most
+	 * sequential IO pattern. We don't bother with the optimization when
+	 * reshaping as the performance benefit is not worth the complexity.
+	 */
+	if (likely(conf->reshape_progress == MaxSector))
+		logical_sector = raid5_bio_lowest_chunk_sector(conf, bi);
+	s = (logical_sector - ctx.first_sector) >> RAID5_STRIPE_SHIFT(conf);
+
 	add_wait_queue(&conf->wait_for_overlap, &wait);
 	while (1) {
 		res = make_stripe_request(mddev, conf, &ctx, logical_sector,
@@ -6178,7 +6221,7 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
 			continue;
 		}
 
-		s = find_first_bit(ctx.sectors_to_do, stripe_cnt);
+		s = find_next_bit_wrap(ctx.sectors_to_do, stripe_cnt, s);
 		if (s == stripe_cnt)
 			break;