fs/direct-io.c: minor cleanups in do_blockdev_direct_IO

We already get the block counts and calculate the end block at the
beginning of the function.  Let's use the local variables for
consistency and readability.  No functional changes

[akpm@linux-foundation.org: constify the locals to prevent future slipups]
Link: http://lkml.kernel.org/r/1519638870-17756-1-git-send-email-nborisov@suse.com
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/direct-io.c

@@ -1178,9 +1178,9 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	unsigned blkbits = i_blkbits;
 	unsigned blocksize_mask = (1 << blkbits) - 1;
 	ssize_t retval = -EINVAL;
-	size_t count = iov_iter_count(iter);
+	const size_t count = iov_iter_count(iter);
 	loff_t offset = iocb->ki_pos;
-	loff_t end = offset + count;
+	const loff_t end = offset + count;
 	struct dio *dio;
 	struct dio_submit sdio = { 0, };
 	struct buffer_head map_bh = { 0, };
@@ -1201,7 +1201,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 	}
 
 	/* watch out for a 0 len io from a tricksy fs */
-	if (iov_iter_rw(iter) == READ && !iov_iter_count(iter))
+	if (iov_iter_rw(iter) == READ && !count)
 		return 0;
 
 	dio = kmem_cache_alloc(dio_cache, GFP_KERNEL);
@@ -1318,8 +1318,7 @@ do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode,
 
 	dio->should_dirty = (iter->type == ITER_IOVEC);
 	sdio.iter = iter;
-	sdio.final_block_in_request =
-		(offset + iov_iter_count(iter)) >> blkbits;
+	sdio.final_block_in_request = end >> blkbits;
 
 	/*
 	 * In case of non-aligned buffers, we may need 2 more