block: remove the NULL bdev check in bdev_read_only

Only a single caller can end up in bdev_read_only, so move the check
there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -1657,11 +1657,8 @@ EXPORT_SYMBOL(set_disk_ro);
 
 int bdev_read_only(struct block_device *bdev)
 {
-	if (!bdev)
-		return 0;
 	return bdev->bd_read_only;
 }
-
 EXPORT_SYMBOL(bdev_read_only);
 
 /*

fs/super.c

@@ -865,7 +865,8 @@ int reconfigure_super(struct fs_context *fc)
 
 	if (fc->sb_flags_mask & SB_RDONLY) {
 #ifdef CONFIG_BLOCK
-		if (!(fc->sb_flags & SB_RDONLY) && bdev_read_only(sb->s_bdev))
+		if (!(fc->sb_flags & SB_RDONLY) && sb->s_bdev &&
+		    bdev_read_only(sb->s_bdev))
 			return -EACCES;
 #endif