const: make block_device_operations const

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ext2/xip.c b/fs/ext2/xip.c
index b72b858..c18fbf3 100644
--- a/fs/ext2/xip.c
+++ b/fs/ext2/xip.c
@@ -20,7 +20,7 @@
 		      void **kaddr, unsigned long *pfn)
 {
 	struct block_device *bdev = inode->i_sb->s_bdev;
-	struct block_device_operations *ops = bdev->bd_disk->fops;
+	const struct block_device_operations *ops = bdev->bd_disk->fops;
 	sector_t sector;
 
 	sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */