Merge pull request #674 from dmcgowan/fs-hardlink-unmodified

Fix hardlinks in tars for unmodified files

fs/copy.go

@@ -65,7 +65,7 @@ func copyDirectory(dst, src string, inodes map[uint64]string) error {
 			}
 			continue
 		case (fi.Mode() & os.ModeType) == 0:
-			link, err := GetLinkSource(target, fi, inodes)
+			link, err := getLinkSource(target, fi, inodes)
 			if err != nil {
 				return errors.Wrap(err, "failed to get hardlink")
 			}

fs/diff.go

@@ -16,9 +16,13 @@ import (
 type ChangeKind int
 
 const (
+	// ChangeKindUnmodified represents an unmodified
+	// file
+	ChangeKindUnmodified = iota
+
 	// ChangeKindAdd represents an addition of
 	// a file
-	ChangeKindAdd = iota
+	ChangeKindAdd
 
 	// ChangeKindModify represents a change to
 	// an existing file
@@ -31,6 +35,8 @@ const (
 
 func (k ChangeKind) String() string {
 	switch k {
+	case ChangeKindUnmodified:
+		return "unmodified"
 	case ChangeKindAdd:
 		return "add"
 	case ChangeKindModify:
@@ -287,7 +293,10 @@ func doubleWalkDiff(ctx context.Context, changeFn ChangeFunc, a, b string) (err
 				f1 = nil
 				f2 = nil
 				if same {
-					continue
+					if !isLinked(f) {
+						continue
+					}
+					k = ChangeKindUnmodified
 				}
 			}
 			if err := changeFn(k, p, f, nil); err != nil {

fs/diff_linux.go

@@ -90,3 +90,11 @@ func compareCapabilities(p1, p2 string) (bool, error) {
 	}
 	return bytes.Equal(c1, c2), nil
 }
+
+func isLinked(f os.FileInfo) bool {
+	s, ok := f.Sys().(*syscall.Stat_t)
+	if !ok {
+		return false
+	}
+	return !f.IsDir() && s.Nlink > 1
+}

fs/diff_windows.go

@@ -1,5 +1,7 @@
 package fs
 
+import "os"
+
 func detectDirDiff(upper, lower string) *diffDirOptions {
 	return nil
 }
@@ -13,3 +15,7 @@ func compareCapabilities(p1, p2 string) (bool, error) {
 	// TODO: Use windows equivalent
 	return true, nil
 }
+
+func isLinked(os.FileInfo) bool {
+	return false
+}

fs/hardlink.go

@@ -2,11 +2,26 @@ package fs
 
 import "os"
 
-// GetLinkSource returns a path for the given name and
+// GetLinkID returns an identifier representing the node a hardlink is pointing
+// to. If the file is not hard linked then 0 will be returned.
+func GetLinkInfo(fi os.FileInfo) (uint64, bool) {
+	return getLinkInfo(fi)
+}
+
+// getLinkSource returns a path for the given name and
 // file info to its link source in the provided inode
 // map. If the given file name is not in the map and
 // has other links, it is added to the inode map
 // to be a source for other link locations.
-func GetLinkSource(name string, fi os.FileInfo, inodes map[uint64]string) (string, error) {
-	return getHardLink(name, fi, inodes)
+func getLinkSource(name string, fi os.FileInfo, inodes map[uint64]string) (string, error) {
+	inode, isHardlink := getLinkInfo(fi)
+	if !isHardlink {
+		return "", nil
+	}
+
+	path, ok := inodes[inode]
+	if !ok {
+		inodes[inode] = name
+	}
+	return path, nil
 }

fs/hardlink_unix.go

@@ -3,31 +3,15 @@
 package fs
 
 import (
-	"errors"
 	"os"
 	"syscall"
 )
 
-func getHardLink(name string, fi os.FileInfo, inodes map[uint64]string) (string, error) {
-	if fi.IsDir() {
-		return "", nil
-	}
-
+func getLinkInfo(fi os.FileInfo) (uint64, bool) {
 	s, ok := fi.Sys().(*syscall.Stat_t)
 	if !ok {
-		return "", errors.New("unsupported stat type")
+		return 0, false
 	}
 
-	// If inode is not hardlinked, no reason to lookup or save inode
-	if s.Nlink == 1 {
-		return "", nil
-	}
-
-	inode := uint64(s.Ino)
-
-	path, ok := inodes[inode]
-	if !ok {
-		inodes[inode] = name
-	}
-	return path, nil
+	return uint64(s.Ino), !fi.IsDir() && s.Nlink > 1
 }

fs/hardlink_windows.go

@@ -2,6 +2,6 @@ package fs
 
 import "os"
 
-func getHardLink(string, os.FileInfo, map[uint64]string) (string, error) {
-	return "", nil
+func getLinkInfo(fi os.FileInfo) (uint64, bool) {
+	return 0, false
 }