mount: record a hard link's looked-up names on its inode

Lookup mapped a second name of a hard-linked file to the existing inode
without adding it to the inode's names, so GetAllPaths missed it and the
final forget left it mapped to a released inode.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

weed/mount/inode_to_path.go

@@ -201,9 +201,13 @@ func (i *InodeToPath) Lookup(path util.FullPath, unixTime int64, isDirectory boo
 	}
 	i.path2inode[path] = inode
 
-	if _, found := i.inode2path[inode]; found {
+	if ie, known := i.inode2path[inode]; known {
+		// Another name of a hard link the table already holds.
+		if !found {
+			ie.addPath(path)
+		}
 		if isLookup {
-			i.inode2path[inode].nlookup++
+			ie.nlookup++
 		}
 	} else {
 		nlookup := uint64(0)

weed/mount/inode_to_path_test.go

@@ -208,3 +208,25 @@ func TestMovePathWithNoSourceLeavesTheTarget(t *testing.T) {
 		t.Errorf("/a/g.txt resolves to %d (found %v), want %d", got, found, inode)
 	}
 }
+
+// A second hard link name found by a lookup belongs to the inode, so it is
+// reported with the others and released by the final forget.
+func TestLookupRecordsHardLinkNames(t *testing.T) {
+	table := NewInodeToPath(util.FullPath("/"), 0)
+	inode := table.Lookup("/a", 1, false, true, 42, true)
+	if got := table.Lookup("/b", 1, false, true, 42, true); got != inode {
+		t.Fatalf("second name got inode %d, want %d", got, inode)
+	}
+	table.Lookup("/b", 1, false, true, 42, true)
+	if got := table.GetAllPaths(inode); len(got) != 2 || got[0] != "/a" || got[1] != "/b" {
+		t.Fatalf("paths %v, want [/a /b]", got)
+	}
+	table.RemovePath("/a", nil)
+	if got, status := table.GetPath(inode); status != fuse.OK || got != "/b" {
+		t.Fatalf("after removing /a the inode answers to %q (%v), want /b", got, status)
+	}
+	table.Forget(inode, 3, nil, nil)
+	if _, found := table.GetInode("/b"); found {
+		t.Fatal("the final forget left /b mapped to a released inode")
+	}
+}