block: move the raid_partial_stripes_expensive flag into the features field

Move the raid_partial_stripes_expensive flags into the features field to
reclaim a little bit of space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20240619154623.450048-7-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

block/blk-settings.c

@@ -556,10 +556,6 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 		ret = -1;
 	}
 
-	t->raid_partial_stripes_expensive =
-		max(t->raid_partial_stripes_expensive,
-		    b->raid_partial_stripes_expensive);
-
 	/* Find lowest common alignment_offset */
 	t->alignment_offset = lcm_not_zero(t->alignment_offset, alignment)
 		% max(t->physical_block_size, t->io_min);

drivers/md/bcache/super.c

@@ -1416,8 +1416,8 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
 	}
 
 	if (bdev_io_opt(dc->bdev))
-		dc->partial_stripes_expensive =
-			q->limits.raid_partial_stripes_expensive;
+		dc->partial_stripes_expensive = q->limits.features &
+			BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
 
 	ret = bcache_device_init(&dc->disk, block_size,
 			 bdev_nr_sectors(dc->bdev) - dc->sb.data_offset,

drivers/md/raid5.c

@@ -7707,7 +7707,7 @@ static int raid5_set_limits(struct mddev *mddev)
 	blk_set_stacking_limits(&lim);
 	lim.io_min = mddev->chunk_sectors << 9;
 	lim.io_opt = lim.io_min * (conf->raid_disks - conf->max_degraded);
-	lim.raid_partial_stripes_expensive = 1;
+	lim.features |= BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
 	lim.discard_granularity = stripe;
 	lim.max_write_zeroes_sectors = 0;
 	mddev_stack_rdev_limits(mddev, &lim, 0);

include/linux/blkdev.h

@@ -328,14 +328,18 @@ enum {
 
 	/* bounce all highmem pages */
 	BLK_FEAT_BOUNCE_HIGH			= (1u << 14),
+
+	/* undocumented magic for bcache */
+	BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE	= (1u << 15),
 };
 
 /*
  * Flags automatically inherited when stacking limits.
  */
 #define BLK_FEAT_INHERIT_MASK \
 	(BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA | BLK_FEAT_ROTATIONAL | \
-	 BLK_FEAT_STABLE_WRITES | BLK_FEAT_ZONED | BLK_FEAT_BOUNCE_HIGH)
+	 BLK_FEAT_STABLE_WRITES | BLK_FEAT_ZONED | BLK_FEAT_BOUNCE_HIGH | \
+	 BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE)
 
 /* internal flags in queue_limits.flags */
 enum {
@@ -377,7 +381,6 @@ struct queue_limits {
 	unsigned short		max_integrity_segments;
 	unsigned short		max_discard_segments;
 
-	unsigned char		raid_partial_stripes_expensive;
 	unsigned int		max_open_zones;
 	unsigned int		max_active_zones;