block: move the bounce flag into the features field

Move the bounce flag into the features field to reclaim a little bit of
space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20240617060532.127975-27-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-settings.c

@@ -479,7 +479,6 @@ int blk_stack_limits(struct queue_limits *t, struct queue_limits *b,
 					b->max_write_zeroes_sectors);
 	t->max_zone_append_sectors = min(queue_limits_max_zone_append_sectors(t),
 					 queue_limits_max_zone_append_sectors(b));
-	t->bounce = max(t->bounce, b->bounce);
 
 	t->seg_boundary_mask = min_not_zero(t->seg_boundary_mask,
 					    b->seg_boundary_mask);

block/blk.h

@@ -394,7 +394,7 @@ struct bio *__blk_queue_bounce(struct bio *bio, struct request_queue *q);
 static inline bool blk_queue_may_bounce(struct request_queue *q)
 {
 	return IS_ENABLED(CONFIG_BOUNCE) &&
-		q->limits.bounce == BLK_BOUNCE_HIGH &&
+		(q->limits.features & BLK_FEAT_BOUNCE_HIGH) &&
 		max_low_pfn >= max_pfn;
 }
 

drivers/scsi/scsi_lib.c

@@ -1986,7 +1986,7 @@ void scsi_init_limits(struct Scsi_Host *shost, struct queue_limits *lim)
 		shost->dma_alignment, dma_get_cache_alignment() - 1);
 
 	if (shost->no_highmem)
-		lim->bounce = BLK_BOUNCE_HIGH;
+		lim->features |= BLK_FEAT_BOUNCE_HIGH;
 
 	dma_set_seg_boundary(dev, shost->dma_boundary);
 	dma_set_max_seg_size(dev, shost->max_segment_size);

include/linux/blkdev.h

@@ -325,14 +325,17 @@ enum {
 
 	/* skip this queue in blk_mq_(un)quiesce_tagset */
 	BLK_FEAT_SKIP_TAGSET_QUIESCE		= (1u << 13),
+
+	/* bounce all highmem pages */
+	BLK_FEAT_BOUNCE_HIGH			= (1u << 14),
 };
 
 /*
  * 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_STABLE_WRITES | BLK_FEAT_ZONED | BLK_FEAT_BOUNCE_HIGH)
 
 /* internal flags in queue_limits.flags */
 enum {
@@ -352,7 +355,6 @@ enum blk_bounce {
 struct queue_limits {
 	unsigned int		features;
 	unsigned int		flags;
-	enum blk_bounce		bounce;
 	unsigned long		seg_boundary_mask;
 	unsigned long		virt_boundary_mask;