Introduce skip value support for --hardlinks flag

cmd/copy.go

@@ -1980,5 +1980,10 @@ func init() {
 		"Specifies how hardlinks should be handled. "+
 			"\n This flag is only applicable when downloading from an Azure NFS file share, uploading "+
 			"to an Azure Files NFS share, or performing service-to-service copies involving Azure Files NFS. \n"+
-			"\n The only supported option is 'follow' (default), which copies hardlinks as regular, independent files at the destination.")
+			"\n The supported option are 'follow' (default), 'skip' and 'preserve'. \n"+
+			"  'follow' means that the hardlinked files are transferred as separate files. \n"+
+			"  'skip' means that all the hardlinked files are skipped. \n"+
+			"  'preserve' means that the first hardlinked file is transferred, and the other files are created as hardlinks to that file at the destination. \n"+
+			"\n Note: \n"+
+			"  When using 'preserve', the source and destination must be on a file system that supports hardlinks. \n")
 }

cmd/copyValidation.go

@@ -103,7 +103,7 @@ func (cooked *CookedCopyCmdArgs) validate() (err error) {
 	} else {
 		if err := performSMBSpecificValidation(
 			cooked.FromTo, cooked.preservePermissions, cooked.preserveInfo,
-			cooked.preservePOSIXProperties); err != nil {
+			cooked.preservePOSIXProperties, &cooked.hardlinks); err != nil {
 			return err
 		}
 

cmd/flagsValidation.go

@@ -170,10 +170,10 @@ func performNFSSpecificValidation(fromTo common.FromTo,
 		PreservePermissionsFlag); err != nil {
 		return err
 	}
-	// TODO: Add this check in Phase-3 which targets to support hardlinks for NFS copy.
-	// if err = validateAndAdjustHardlinksFlag(hardlinkHandling, fromTo); err != nil {
-	// 	return err
-	// }
+
+	if err = validateAndAdjustHardlinksFlag(hardlinkHandling, fromTo); err != nil {
+		return err
+	}
 
 	if err = validateSymlinkFlag(symlinkHandling == common.ESymlinkHandlingType.Follow(),
 		fromTo); err != nil {
@@ -198,7 +198,8 @@ func performNFSSpecificValidation(fromTo common.FromTo,
 func performSMBSpecificValidation(fromTo common.FromTo,
 	preservePermissions common.PreservePermissionsOption,
 	preserveInfo bool,
-	preservePOSIXProperties bool) (err error) {
+	preservePOSIXProperties bool,
+	hardlinkHandling *common.HardlinkHandlingType) (err error) {
 
 	if err = validatePreserveSMBPropertyOption(preserveInfo,
 		fromTo,
@@ -214,10 +215,9 @@ func performSMBSpecificValidation(fromTo common.FromTo,
 		return err
 	}
 
-	// TODO: Add this check in Phase-3 which targets to support hardlinks for NFS copy.
-	// if err = validateAndAdjustHardlinksFlag(hardlinkHandling, fromTo); err != nil {
-	// 	return err
-	// }
+	if err = validateAndAdjustHardlinksFlag(hardlinkHandling, fromTo); err != nil {
+		return err
+	}
 	return nil
 }
 
@@ -236,61 +236,63 @@ func validateSymlinkFlag(followSymlinks bool, fromTo common.FromTo) error {
 // transfer direction (upload, download, S2S), and source/destination types (NFS, SMB, local).
 // Returns an error if the configuration is unsupported.
 // This function will be added as part of Phase-3 which targets to support hardlinks for NFS copy.
-// func validateAndAdjustHardlinksFlag(option *common.HardlinkHandlingType, fromTo common.FromTo) error {
-// 	if !fromTo.IsNFS() {
-// 		return nil
-// 	}
-
-// 	// NFS<->SMB special case: force skip
-// 	if (fromTo == common.EFromTo.FileNFSFileSMB() || fromTo == common.EFromTo.FileSMBFileNFS()) &&
-// 		*option != common.SkipHardlinkHandlingType {
-// 		return fmt.Errorf(
-// 			"For NFS->SMB and SMB->NFS transfers, '--hardlinks' must be set to 'skip'. " +
-// 				"Hardlinked files are not supported between NFS and SMB and will always be skipped. " +
-// 				"Please re-run with '--hardlinks=skip'.",
-// 		)
-// 	}
-
-// 	// OS check: hardlinks handling only supported on Linux in case of upload and download
-// 	if runtime.GOOS != "linux" && !fromTo.IsS2S() {
-// 		return fmt.Errorf("The --hardlinks option is only supported on Linux.")
-// 	}
-
-// 	switch {
-// 	case fromTo.IsDownload():
-// 		// Must be NFS -> Local Linux
-// 		if fromTo.From() != common.ELocation.FileNFS() {
-// 			return fmt.Errorf("For downloads, '--hardlinks' is only supported from an NFS file share to a Linux filesystem.")
-// 		}
-
-// 	case fromTo.IsUpload():
-// 		// Must be Local Linux -> NFS
-// 		if fromTo.To() != common.ELocation.FileNFS() {
-// 			return fmt.Errorf("For uploads, '--hardlinks' is only supported from a Linux filesystem to an NFS file share.")
-// 		}
-
-// 	case fromTo.IsS2S():
-// 		// Allowed: NFS<->NFS, NFS->SMB, SMB->NFS
-// 		validPairs := map[common.FromTo]bool{
-// 			common.EFromTo.FileNFSFileNFS(): true,
-// 			common.EFromTo.FileNFSFileSMB(): true,
-// 			common.EFromTo.FileSMBFileNFS(): true,
-// 		}
-// 		if !validPairs[fromTo] {
-// 			return fmt.Errorf("For S2S transfers, '--hardlinks' is only supported for NFS<->NFS, NFS->SMB, and SMB->NFS.")
-// 		}
-// 	}
-
-// 	// Info messages
-// 	switch *option {
-// 	case common.SkipHardlinkHandlingType:
-// 		glcm.Info("The --hardlinks option is set to 'skip'. Hardlinked files will be skipped.")
-// 	case common.DefaultHardlinkHandlingType:
-// 		glcm.Info("The --hardlinks option is set to 'follow'. Hardlinked files will be copied as regular files.")
-// 	}
-
-// 	return nil
-// }
+func validateAndAdjustHardlinksFlag(option *common.HardlinkHandlingType, fromTo common.FromTo) error {
+	if !fromTo.IsNFS() {
+		return nil
+	}
+
+	// OS check: hardlinks handling only supported on Linux in case of upload and download
+	if runtime.GOOS != "linux" && !fromTo.IsS2S() {
+		return fmt.Errorf("The --hardlinks option is only supported on Linux.")
+	}
+
+	// NFS<->SMB special case: force skip
+	if (fromTo == common.EFromTo.FileNFSFileSMB() || fromTo == common.EFromTo.FileSMBFileNFS()) &&
+		*option == common.PreserveHardlinkHandlingType {
+		return fmt.Errorf(
+			"For NFS->SMB and SMB->NFS transfers, '--hardlinks' must be set to 'skip'. " +
+				"Hardlinked files are not supported between NFS and SMB and will always be skipped. " +
+				"Please re-run with '--hardlinks=skip'.",
+		)
+	}
+
+	switch {
+	case fromTo.IsDownload():
+		// Must be NFS -> Local Linux
+		if fromTo.From() != common.ELocation.FileNFS() {
+			return fmt.Errorf("For downloads, '--hardlinks' is only supported from an NFS file share to a Linux filesystem.")
+		}
+
+	case fromTo.IsUpload():
+		// Must be Local Linux -> NFS
+		if fromTo.To() != common.ELocation.FileNFS() {
+			return fmt.Errorf("For uploads, '--hardlinks' is only supported from a Linux filesystem to an NFS file share.")
+		}
+
+	case fromTo.IsS2S():
+		// Allowed: NFS<->NFS, NFS->SMB, SMB->NFS
+		validPairs := map[common.FromTo]bool{
+			common.EFromTo.FileNFSFileNFS(): true,
+			common.EFromTo.FileNFSFileSMB(): true,
+			common.EFromTo.FileSMBFileNFS(): true,
+		}
+		if !validPairs[fromTo] {
+			return fmt.Errorf("for S2S transfers, '--hardlinks' is only supported for NFS<->NFS, NFS->SMB, and SMB->NFS.")
+		}
+	}
+
+	// Info messages
+	switch *option {
+	case common.SkipHardlinkHandlingType:
+		glcm.Info("The --hardlinks option is set to 'skip'. Hardlinked files will be skipped.")
+	case common.DefaultHardlinkHandlingType:
+		glcm.Info("The --hardlinks option is set to 'follow'. Hardlinked files will be copied as regular files.")
+	case common.PreserveHardlinkHandlingType:
+		glcm.Info("The --hardlinks option is set to 'preserve'. Hardlinked files will be preserved as hardlinks at the destination.")
+	}
+
+	return nil
+}
 
 func isUnsupportedPlatformForNFS(fromTo common.FromTo) (bool, error) {
 	// upload and download is not supported for NFS on non-linux systems

cmd/sync.go

@@ -305,14 +305,15 @@ func (cooked *cookedSyncCmdArgs) validate() (err error) {
 	} else {
 		if err := performSMBSpecificValidation(
 			cooked.fromTo, cooked.preservePermissions, cooked.preserveInfo,
-			cooked.preservePOSIXProperties); err != nil {
+			cooked.preservePOSIXProperties,
+			&cooked.hardlinks); err != nil {
 			return err
 		}
 
 		if cooked.symlinkHandling == common.ESymlinkHandlingType.Follow() {
-			return fmt.Errorf("The '--follow-symlink' flag is not applicable for sync operations.")
+			return fmt.Errorf("the '--follow-symlink' flag is not applicable for sync operations")
 		} else if cooked.symlinkHandling == common.ESymlinkHandlingType.Preserve() {
-			return fmt.Errorf("The '--preserve-symlink' flag is not applicable for sync operations.")
+			return fmt.Errorf("the '--preserve-symlink' flag is not applicable for sync operations")
 		}
 	}
 

common/fe-ste-models.go

@@ -1595,6 +1595,7 @@ var EHardlinkHandlingType = HardlinkHandlingType(0)
 
 var DefaultHardlinkHandlingType = EHardlinkHandlingType.Follow()
 var SkipHardlinkHandlingType = EHardlinkHandlingType.Skip()
+var PreserveHardlinkHandlingType = EHardlinkHandlingType.Preserve()
 
 type HardlinkHandlingType uint8
 
@@ -1608,6 +1609,11 @@ func (HardlinkHandlingType) Skip() HardlinkHandlingType {
 	return HardlinkHandlingType(1)
 }
 
+// Skip means skip the hardlinks and do not copy them to the destination
+func (HardlinkHandlingType) Preserve() HardlinkHandlingType {
+	return HardlinkHandlingType(2)
+}
+
 func (pho HardlinkHandlingType) String() string {
 	return enum.StringInt(pho, reflect.TypeOf(pho))
 }

e2etest/newe2e_task_validation.go

@@ -271,6 +271,19 @@ func ValidateHardlinksConvertedCount(a Asserter, stdOut AzCopyStdout, expected u
 	return
 }
 
+func ValidateHardlinksSkippedCount(a Asserter, stdOut AzCopyStdout, expected uint32) {
+	if dryrunner, ok := a.(DryrunAsserter); ok && dryrunner.Dryrun() {
+		return
+	}
+
+	parsedStdout := GetTypeOrAssert[*AzCopyParsedCopySyncRemoveStdout](a, stdOut)
+	hardlinksSkippedCount := parsedStdout.FinalStatus.SkippedHardlinkCount
+	if hardlinksSkippedCount != expected {
+		a.Error(fmt.Sprintf("expected hardlink skipped count (%d) received count (%d)", expected, hardlinksSkippedCount))
+	}
+	return
+}
+
 func ValidateMessageOutput(a Asserter, stdout AzCopyStdout, message string, shouldContain bool) {
 	if dryrunner, ok := a.(DryrunAsserter); ok && dryrunner.Dryrun() {
 		return