Reinstate "GFS2: free disk inode which is deleted by remote node -V2"

It turns out that reverting commit 970343cd ("GFS2: free disk inode
which is deleted by remote node -V2") causes a regression related to
evicting inodes that were unlinked on a different cluster node.

We could also have simply added a call to d_mark_dontcache() to function
gfs2_try_evict(), but the original pre-revert code is better tested and
proven.

This reverts commit 445cb127.
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/dentry.c

@@ -83,8 +83,26 @@ static int gfs2_dhash(const struct dentry *dentry, struct qstr *str)
 	return 0;
 }
 
+static int gfs2_dentry_delete(const struct dentry *dentry)
+{
+	struct gfs2_inode *ginode;
+
+	if (d_really_is_negative(dentry))
+		return 0;
+
+	ginode = GFS2_I(d_inode(dentry));
+	if (!gfs2_holder_initialized(&ginode->i_iopen_gh))
+		return 0;
+
+	if (test_bit(GLF_DEMOTE, &ginode->i_iopen_gh.gh_gl->gl_flags))
+		return 1;
+
+	return 0;
+}
+
 const struct dentry_operations gfs2_dops = {
 	.d_revalidate = gfs2_drevalidate,
 	.d_hash = gfs2_dhash,
+	.d_delete = gfs2_dentry_delete,
 };