mm/filemap: pass inclusive 'end_byte' parameter to filemap_range_has_page

The 'end_byte' parameter of filemap_range_has_page is required to be
inclusive, so follow the rule.

Link: http://lkml.kernel.org/r/1548678679-18122-1-git-send-email-zhengbin13@huawei.com
Fixes: 6be96d3a ("fs: return if direct I/O will trigger writeback")
Signed-off-by: Nzhengbin <zhengbin13@huawei.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NMatthew Wilcox <willy@infradead.org>
Acked-by: NChristoph Hellwig <hch@lst.de>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hou Tao <houtao1@huawei.com>
Cc: zhangyi (F) <yi.zhang@huawei.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/filemap.c

@@ -3071,7 +3071,7 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_flags & IOCB_NOWAIT) {
 		/* If there are pages to writeback, return */
 		if (filemap_range_has_page(inode->i_mapping, pos,
-					   pos + write_len))
+					   pos + write_len - 1))
 			return -EAGAIN;
 	} else {
 		written = filemap_write_and_wait_range(mapping, pos,