md/raid5: implement pers->bitmap_sector()

Bitmap is used for the whole array for raid1/raid10, hence IO for the
array can be used directly for bitmap. However, bitmap is used for
underlying disks for raid5, hence IO for the array can't be used
directly for bitmap.

Implement pers->bitmap_sector() for raid5 to convert IO ranges from the
array to the underlying disks.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20250109015145.158868-5-yukuai1@huaweicloud.com
Signed-off-by: Song Liu <song@kernel.org>

drivers/md/raid5.c

@@ -5918,6 +5918,54 @@ static enum reshape_loc get_reshape_loc(struct mddev *mddev,
 	return LOC_BEHIND_RESHAPE;
 }
 
+static void raid5_bitmap_sector(struct mddev *mddev, sector_t *offset,
+				unsigned long *sectors)
+{
+	struct r5conf *conf = mddev->private;
+	sector_t start = *offset;
+	sector_t end = start + *sectors;
+	sector_t prev_start = start;
+	sector_t prev_end = end;
+	int sectors_per_chunk;
+	enum reshape_loc loc;
+	int dd_idx;
+
+	sectors_per_chunk = conf->chunk_sectors *
+		(conf->raid_disks - conf->max_degraded);
+	start = round_down(start, sectors_per_chunk);
+	end = round_up(end, sectors_per_chunk);
+
+	start = raid5_compute_sector(conf, start, 0, &dd_idx, NULL);
+	end = raid5_compute_sector(conf, end, 0, &dd_idx, NULL);
+
+	/*
+	 * For LOC_INSIDE_RESHAPE, this IO will wait for reshape to make
+	 * progress, hence it's the same as LOC_BEHIND_RESHAPE.
+	 */
+	loc = get_reshape_loc(mddev, conf, prev_start);
+	if (likely(loc != LOC_AHEAD_OF_RESHAPE)) {
+		*offset = start;
+		*sectors = end - start;
+		return;
+	}
+
+	sectors_per_chunk = conf->prev_chunk_sectors *
+		(conf->previous_raid_disks - conf->max_degraded);
+	prev_start = round_down(prev_start, sectors_per_chunk);
+	prev_end = round_down(prev_end, sectors_per_chunk);
+
+	prev_start = raid5_compute_sector(conf, prev_start, 1, &dd_idx, NULL);
+	prev_end = raid5_compute_sector(conf, prev_end, 1, &dd_idx, NULL);
+
+	/*
+	 * for LOC_AHEAD_OF_RESHAPE, reshape can make progress before this IO
+	 * is handled in make_stripe_request(), we can't know this here hence
+	 * we set bits for both.
+	 */
+	*offset = min(start, prev_start);
+	*sectors = max(end, prev_end) - *offset;
+}
+
 static enum stripe_result make_stripe_request(struct mddev *mddev,
 		struct r5conf *conf, struct stripe_request_ctx *ctx,
 		sector_t logical_sector, struct bio *bi)
@@ -8966,6 +9014,7 @@ static struct md_personality raid6_personality =
 	.takeover	= raid6_takeover,
 	.change_consistency_policy = raid5_change_consistency_policy,
 	.prepare_suspend = raid5_prepare_suspend,
+	.bitmap_sector	= raid5_bitmap_sector,
 };
 static struct md_personality raid5_personality =
 {
@@ -8991,6 +9040,7 @@ static struct md_personality raid5_personality =
 	.takeover	= raid5_takeover,
 	.change_consistency_policy = raid5_change_consistency_policy,
 	.prepare_suspend = raid5_prepare_suspend,
+	.bitmap_sector	= raid5_bitmap_sector,
 };
 
 static struct md_personality raid4_personality =
@@ -9017,6 +9067,7 @@ static struct md_personality raid4_personality =
 	.takeover	= raid4_takeover,
 	.change_consistency_policy = raid5_change_consistency_policy,
 	.prepare_suspend = raid5_prepare_suspend,
+	.bitmap_sector	= raid5_bitmap_sector,
 };
 
 static int __init raid5_init(void)