ext4: fix off-by-in in loop termination in ext4_find_unwritten_pgoff()

There is an off-by-one error in loop termination conditions in
ext4_find_unwritten_pgoff() since 'end' may index a page beyond end of
desired range if 'endoff' is page aligned. It doesn't have any visible
effects but still it is good to fix it.
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/file.c

@@ -474,7 +474,7 @@ static int ext4_find_unwritten_pgoff(struct inode *inode,
 	endoff = (loff_t)end_blk << blkbits;
 
 	index = startoff >> PAGE_SHIFT;
-	end = endoff >> PAGE_SHIFT;
+	end = (endoff - 1) >> PAGE_SHIFT;
 
 	pagevec_init(&pvec, 0);
 	do {