Fix a minor bug in the previous patch

The logic requires that we mark the glock dirty in page_mkwrite
otherwise we might not flush correctly in the case that no
allocation was required in the process of dirying the page.
Also we need to set the shared write flag early for the same
reason.
Signed-off-by: NSteven Whitehouse <swhiteho@redhat.com>

fs/gfs2/ops_file.c

@@ -355,6 +355,9 @@ static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 	if (ret)
 		goto out;
 
+	set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
+	set_bit(GIF_SW_PAGED, &ip->i_flags);
+
 	ret = gfs2_write_alloc_required(ip, pos, PAGE_CACHE_SIZE, &alloc_required);
 	if (ret || !alloc_required)
 		goto out_unlock;
@@ -395,8 +398,6 @@ static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct page *page)
 			goto out_unlock_page;
 	}
 	ret = gfs2_allocate_page_backing(page);
-	if (!ret)
-		set_bit(GIF_SW_PAGED, &ip->i_flags);
 
 out_unlock_page:
 	unlock_page(page);