[PATCH] give hugetlbfs a set_page_dirty a_op

Seems that nobody has tested direct IO into hugetlb pages yet.  The VFS gets
upset about running set_page_dirty() against a non-uptodate page.

So give hugetlbfs inodes a private no-op ->set_page_dirty() to isolate them
from all that.

fs/hugetlbfs/inode.c

@@ -450,10 +450,19 @@ static int hugetlbfs_symlink(struct inode * dir, struct dentry *dentry, const ch
 	return error;
 }
 
+/*
+ * For direct-IO reads into hugetlb pages
+ */
+int hugetlbfs_set_page_dirty(struct page *page)
+{
+	return 0;
+}
+
 static struct address_space_operations hugetlbfs_aops = {
 	.readpage	= hugetlbfs_readpage,
 	.prepare_write	= hugetlbfs_prepare_write,
-	.commit_write	= hugetlbfs_commit_write
+	.commit_write	= hugetlbfs_commit_write,
+	.set_page_dirty	= hugetlbfs_set_page_dirty,
 };
 
 struct file_operations hugetlbfs_file_operations = {