block: add a bdev_stable_writes helper

Add a helper to check the stable writes flag based on the block_device
instead of having to poke into the block layer internal request_queue.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220415045258.199825-15-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm-table.c

@@ -1950,9 +1950,7 @@ static int device_requires_stable_pages(struct dm_target *ti,
 					struct dm_dev *dev, sector_t start,
 					sector_t len, void *data)
 {
-	struct request_queue *q = bdev_get_queue(dev->bdev);
-
-	return blk_queue_stable_writes(q);
+	return bdev_stable_writes(dev->bdev);
 }
 
 int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,

fs/super.c

@@ -1204,7 +1204,7 @@ static int set_bdev_super(struct super_block *s, void *data)
 	s->s_dev = s->s_bdev->bd_dev;
 	s->s_bdi = bdi_get(s->s_bdev->bd_disk->bdi);
 
-	if (blk_queue_stable_writes(s->s_bdev->bd_disk->queue))
+	if (bdev_stable_writes(s->s_bdev))
 		s->s_iflags |= SB_I_STABLE_WRITES;
 	return 0;
 }

include/linux/blkdev.h

@@ -1330,6 +1330,12 @@ static inline bool bdev_nonrot(struct block_device *bdev)
 	return blk_queue_nonrot(bdev_get_queue(bdev));
 }
 
+static inline bool bdev_stable_writes(struct block_device *bdev)
+{
+	return test_bit(QUEUE_FLAG_STABLE_WRITES,
+			&bdev_get_queue(bdev)->queue_flags);
+}
+
 static inline bool bdev_write_cache(struct block_device *bdev)
 {
 	return test_bit(QUEUE_FLAG_WC, &bdev_get_queue(bdev)->queue_flags);

mm/swapfile.c

@@ -3065,7 +3065,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 		goto bad_swap_unlock_inode;
 	}
 
-	if (p->bdev && blk_queue_stable_writes(p->bdev->bd_disk->queue))
+	if (p->bdev && bdev_stable_writes(p->bdev))
 		p->flags |= SWP_STABLE_WRITES;
 
 	if (p->bdev && p->bdev->bd_disk->fops->rw_page)