block: move integrity information into queue_limits

Move the integrity information into the queue limits so that it can be
set atomically with other queue limits, and that the sysfs changes to
the read_verify and write_generate flags are properly synchronized.
This also allows to provide a more useful helper to stack the integrity
fields, although it still is separate from the main stacking function
as not all stackable devices want to inherit the integrity settings.
Even with that it greatly simplifies the code in md and dm.

Note that the integrity field is moved as-is into the queue limits.
While there are good arguments for removing the separate blk_integrity
structure, this would cause a lot of churn and might better be done at a
later time if desired.  However the integrity field in the queue_limits
structure is now unconditional so that various ifdefs can be avoided or
replaced with IS_ENABLED().  Given that tiny size of it that seems like
a worthwhile trade off.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20240613084839.1044015-13-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blkdev.h

@@ -334,6 +334,8 @@ struct queue_limits {
 	 * due to possible offsets.
 	 */
 	unsigned int		dma_alignment;
+
+	struct blk_integrity	integrity;
 };
 
 typedef int (*report_zones_cb)(struct blk_zone *zone, unsigned int idx,
@@ -419,10 +421,6 @@ struct request_queue {
 
 	struct queue_limits	limits;
 
-#ifdef  CONFIG_BLK_DEV_INTEGRITY
-	struct blk_integrity integrity;
-#endif	/* CONFIG_BLK_DEV_INTEGRITY */
-
 #ifdef CONFIG_PM
 	struct device		*dev;
 	enum rpm_status		rpm_status;
@@ -1300,11 +1298,9 @@ static inline bool bdev_stable_writes(struct block_device *bdev)
 {
 	struct request_queue *q = bdev_get_queue(bdev);
 
-#ifdef CONFIG_BLK_DEV_INTEGRITY
-	/* BLK_INTEGRITY_CSUM_NONE is not available in blkdev.h */
-	if (q->integrity.csum_type != 0)
+	if (IS_ENABLED(CONFIG_BLK_DEV_INTEGRITY) &&
+	    q->limits.integrity.csum_type != BLK_INTEGRITY_CSUM_NONE)
 		return true;
-#endif
 	return test_bit(QUEUE_FLAG_STABLE_WRITES, &q->queue_flags);
 }