lib/fs: Unwrap mtimeFile, get fd the "correct" way (ref #6875) (#6877)

lib/fs/basicfs_copy_range.go

@@ -14,6 +14,9 @@ type copyRangeImplementationBasicFile func(src, dst basicFile, srcOffset, dstOff
 
 func copyRangeImplementationForBasicFile(impl copyRangeImplementationBasicFile) copyRangeImplementation {
 	return func(src, dst File, srcOffset, dstOffset, size int64) error {
+		src = unwrap(src)
+		dst = unwrap(dst)
+		// Then see if it's basic files
 		srcFile, srcOk := src.(basicFile)
 		dstFile, dstOk := dst.(basicFile)
 		if !srcOk || !dstOk {
@@ -22,3 +25,38 @@ func copyRangeImplementationForBasicFile(impl copyRangeImplementationBasicFile)
 		return impl(srcFile, dstFile, srcOffset, dstOffset, size)
 	}
 }
+
+func withFileDescriptors(first, second basicFile, fn func(first, second uintptr) (int, error)) (int, error) {
+	fc, err := first.SyscallConn()
+	if err != nil {
+		return 0, err
+	}
+	sc, err := second.SyscallConn()
+	if err != nil {
+		return 0, err
+	}
+	var n int
+	var ferr, serr, fnerr error
+	ferr = fc.Control(func(first uintptr) {
+		serr = sc.Control(func(second uintptr) {
+			n, fnerr = fn(first, second)
+		})
+	})
+	if ferr != nil {
+		return n, ferr
+	}
+	if serr != nil {
+		return n, serr
+	}
+	return n, fnerr
+}
+
+func unwrap(f File) File {
+	for {
+		if wrapped, ok := f.(interface{ unwrap() File }); ok {
+			f = wrapped.unwrap()
+		} else {
+			return f
+		}
+	}
+}

lib/fs/basicfs_copy_range_copyfilerange.go

@@ -29,7 +29,9 @@ func copyRangeCopyFileRange(src, dst basicFile, srcOffset, dstOffset, size int64
 		// appropriately.
 		//
 		// Also, even if explicitly not stated, the same is true for dstOffset
-		n, err := unix.CopyFileRange(int(src.Fd()), &srcOffset, int(dst.Fd()), &dstOffset, int(size), 0)
+		n, err := withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
+			return unix.CopyFileRange(int(srcFd), &srcOffset, int(dstFd), &dstOffset, int(size), 0)
+		})
 		if n == 0 && err == nil {
 			return io.ErrUnexpectedEOF
 		}

lib/fs/basicfs_copy_range_duplicateextents.go

@@ -9,6 +9,7 @@
 package fs
 
 import (
+	"io"
 	"syscall"
 	"unsafe"
 
@@ -46,13 +47,24 @@ type duplicateExtentsData struct {
 func copyRangeDuplicateExtents(src, dst basicFile, srcOffset, dstOffset, size int64) error {
 	var err error
 	// Check that the destination file has sufficient space
-	if fi, err := dst.Stat(); err != nil {
+	dstFi, err := dst.Stat()
+	if err != nil {
 		return err
-	} else if fi.Size() < dstOffset+size {
+	}
+	dstSize := dstFi.Size()
+	if dstSize < dstOffset+size {
 		// set file size. There is a requirements "The destination region must not extend past the end of file."
 		if err = dst.Truncate(dstOffset + size); err != nil {
 			return err
 		}
+		dstSize = dstOffset + size
+	}
+
+	// The source file has to be big enough
+	if fi, err := src.Stat(); err != nil {
+		return err
+	} else if fi.Size() < srcOffset+size {
+		return io.ErrUnexpectedEOF
 	}
 
 	// Requirement
@@ -60,9 +72,25 @@ func copyRangeDuplicateExtents(src, dst basicFile, srcOffset, dstOffset, size in
 	// * cloneRegionSize less than 4GiB.
 	// see https://docs.microsoft.com/windows/win32/fileio/block-cloning
 
+	smallestClusterSize := availableClusterSize[len(availableClusterSize)-1]
+
+	if srcOffset%smallestClusterSize != 0 || dstOffset%smallestClusterSize != 0 {
+		return syscall.EINVAL
+	}
+
+	// Each file gets allocated multiple of "clusterSize" blocks, yet file size determines how much of the last block
+	// is readable/visible.
+	// Copies only happen in block sized chunks, hence you can copy non block sized regions of data to a file, as long
+	// as the regions are copied at the end of the file where the block visibility is adjusted by the file size.
+	if size%smallestClusterSize != 0 && dstOffset+size != dstSize {
+		return syscall.EINVAL
+	}
+
 	// Clone first xGiB region.
 	for size > GiB {
-		err = callDuplicateExtentsToFile(src.Fd(), dst.Fd(), srcOffset, dstOffset, GiB)
+		_, err = withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
+			return 0, callDuplicateExtentsToFile(srcFd, dstFd, srcOffset, dstOffset, GiB)
+		})
 		if err != nil {
 			return wrapError(err)
 		}
@@ -73,7 +101,9 @@ func copyRangeDuplicateExtents(src, dst basicFile, srcOffset, dstOffset, size in
 
 	// Clone tail. First try with 64KiB round up, then fallback to 4KiB.
 	for _, cloneRegionSize := range availableClusterSize {
-		err = callDuplicateExtentsToFile(src.Fd(), dst.Fd(), srcOffset, dstOffset, roundUp(size, cloneRegionSize))
+		_, err = withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
+			return 0, callDuplicateExtentsToFile(srcFd, dstFd, srcOffset, dstOffset, roundUp(size, cloneRegionSize))
+		})
 		if err != nil {
 			continue
 		}
@@ -94,7 +124,7 @@ func wrapError(err error) error {
 // see https://docs.microsoft.com/en-us/windows/win32/api/winioctl/ni-winioctl-fsctl_duplicate_extents_to_file
 //
 // memo: Overflow (cloneRegionSize is greater than file ends) is safe and just ignored by windows.
-func callDuplicateExtentsToFile(src, dst uintptr, srcOffset, dstOffset int64, cloneRegionSize int64) (err error) {
+func callDuplicateExtentsToFile(src, dst uintptr, srcOffset, dstOffset int64, cloneRegionSize int64) error {
 	var (
 		bytesReturned uint32
 		overlapped    windows.Overlapped

lib/fs/basicfs_copy_range_ioctl.go

@@ -4,11 +4,12 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
-// +build !windows,!solaris,!darwin
+// +build linux
 
 package fs
 
 import (
+	"io"
 	"syscall"
 	"unsafe"
 )
@@ -43,6 +44,10 @@ func copyRangeIoctl(src, dst basicFile, srcOffset, dstOffset, size int64) error
 		return err
 	}
 
+	if srcOffset+size > fi.Size() {
+		return io.ErrUnexpectedEOF
+	}
+
 	// https://www.man7.org/linux/man-pages/man2/ioctl_ficlonerange.2.html
 	// If src_length is zero, the ioctl reflinks to the end of the source file.
 	if srcOffset+size == fi.Size() {
@@ -51,20 +56,36 @@ func copyRangeIoctl(src, dst basicFile, srcOffset, dstOffset, size int64) error
 
 	if srcOffset == 0 && dstOffset == 0 && size == 0 {
 		// Optimization for whole file copies.
-		_, _, errNo := syscall.Syscall(syscall.SYS_IOCTL, dst.Fd(), FICLONE, src.Fd())
+		var errNo syscall.Errno
+		_, err := withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
+			_, _, errNo = syscall.Syscall(syscall.SYS_IOCTL, dstFd, FICLONE, srcFd)
+			return 0, nil
+		})
+		// Failure in withFileDescriptors
+		if err != nil {
+			return err
+		}
 		if errNo != 0 {
 			return errNo
 		}
 		return nil
 	}
 
-	params := fileCloneRange{
+	var errNo syscall.Errno
-		srcFd:     int64(src.Fd()),
+	_, err = withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
-		srcOffset: uint64(srcOffset),
+		params := fileCloneRange{
-		srcLength: uint64(size),
+			srcFd:     int64(srcFd),
-		dstOffset: uint64(dstOffset),
+			srcOffset: uint64(srcOffset),
+			srcLength: uint64(size),
+			dstOffset: uint64(dstOffset),
+		}
+		_, _, errNo = syscall.Syscall(syscall.SYS_IOCTL, dstFd, FICLONERANGE, uintptr(unsafe.Pointer(&params)))
+		return 0, nil
+	})
+	// Failure in withFileDescriptors
+	if err != nil {
+		return err
 	}
-	_, _, errNo := syscall.Syscall(syscall.SYS_IOCTL, dst.Fd(), FICLONERANGE, uintptr(unsafe.Pointer(&params)))
 	if errNo != 0 {
 		return errNo
 	}

lib/fs/basicfs_copy_range_sendfile.go

@@ -4,7 +4,7 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
-// +build !windows,!darwin
+// +build linux solaris
 
 package fs
 
@@ -51,7 +51,9 @@ func copyRangeSendFile(src, dst basicFile, srcOffset, dstOffset, size int64) err
 		// following the last byte that was read. If offset is not NULL, then sendfile() does not modify the current
 		// file offset of in_fd; otherwise the current file offset is adjusted to reflect the number of bytes read from
 		// in_fd.
-		n, err := syscall.Sendfile(int(dst.Fd()), int(src.Fd()), &srcOffset, int(size))
+		n, err := withFileDescriptors(dst, src, func(dstFd, srcFd uintptr) (int, error) {
+			return syscall.Sendfile(int(dstFd), int(srcFd), &srcOffset, int(size))
+		})
 		if n == 0 && err == nil {
 			err = io.ErrUnexpectedEOF
 		}

lib/fs/filesystem_copy_range_test.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"math/rand"
 	"os"
+	"path/filepath"
 	"syscall"
 	"testing"
 )
@@ -51,7 +52,7 @@ var (
 			expectedErrors:           nil,
 		},
 		{
-			name:                     "append to end, offsets at start",
+			name:                     "append to end offsets at start",
 			srcSize:                  generationSize,
 			dstSize:                  generationSize,
 			srcOffset:                0,
@@ -124,27 +125,87 @@ var (
 			copySize:                 defaultCopySize * 10,
 			// ioctl returns syscall.EINVAL, rest are wrapped
 			expectedErrors: map[CopyRangeMethod]error{
-				CopyRangeMethodIoctl:           syscall.EINVAL,
+				CopyRangeMethodIoctl:            io.ErrUnexpectedEOF,
-				CopyRangeMethodStandard:        io.ErrUnexpectedEOF,
+				CopyRangeMethodStandard:         io.ErrUnexpectedEOF,
-				CopyRangeMethodCopyFileRange:   io.ErrUnexpectedEOF,
+				CopyRangeMethodCopyFileRange:    io.ErrUnexpectedEOF,
-				CopyRangeMethodSendFile:        io.ErrUnexpectedEOF,
+				CopyRangeMethodSendFile:         io.ErrUnexpectedEOF,
-				CopyRangeMethodAllWithFallback: io.ErrUnexpectedEOF,
+				CopyRangeMethodAllWithFallback:  io.ErrUnexpectedEOF,
+				CopyRangeMethodDuplicateExtents: io.ErrUnexpectedEOF,
 			},
 		},
-		// Non block sized file
 		{
-			name:                     "not block aligned write",
+			name:                     "unaligned source offset unaligned size",
-			srcSize:                  generationSize + 2,
+			srcSize:                  generationSize,
 			dstSize:                  0,
 			srcOffset:                1,
 			dstOffset:                0,
 			srcStartingPos:           0,
 			dstStartingPos:           0,
-			expectedDstSizeAfterCopy: generationSize + 1,
+			expectedDstSizeAfterCopy: defaultCopySize + 1,
-			copySize:                 generationSize + 1,
+			copySize:                 defaultCopySize + 1,
-			// Only fails for ioctl
 			expectedErrors: map[CopyRangeMethod]error{
-				CopyRangeMethodIoctl: syscall.EINVAL,
+				CopyRangeMethodIoctl:            syscall.EINVAL,
+				CopyRangeMethodDuplicateExtents: syscall.EINVAL,
+			},
+		},
+		{
+			name:                     "unaligned source offset aligned size",
+			srcSize:                  generationSize,
+			dstSize:                  0,
+			srcOffset:                1,
+			dstOffset:                0,
+			srcStartingPos:           0,
+			dstStartingPos:           0,
+			expectedDstSizeAfterCopy: defaultCopySize,
+			copySize:                 defaultCopySize,
+			expectedErrors: map[CopyRangeMethod]error{
+				CopyRangeMethodIoctl:            syscall.EINVAL,
+				CopyRangeMethodDuplicateExtents: syscall.EINVAL,
+			},
+		},
+		{
+			name:                     "unaligned destination offset unaligned size",
+			srcSize:                  generationSize,
+			dstSize:                  generationSize,
+			srcOffset:                0,
+			dstOffset:                1,
+			srcStartingPos:           0,
+			dstStartingPos:           0,
+			expectedDstSizeAfterCopy: generationSize,
+			copySize:                 defaultCopySize + 1,
+			expectedErrors: map[CopyRangeMethod]error{
+				CopyRangeMethodIoctl:            syscall.EINVAL,
+				CopyRangeMethodDuplicateExtents: syscall.EINVAL,
+			},
+		},
+		{
+			name:                     "unaligned destination offset aligned size",
+			srcSize:                  generationSize,
+			dstSize:                  generationSize,
+			srcOffset:                0,
+			dstOffset:                1,
+			srcStartingPos:           0,
+			dstStartingPos:           0,
+			expectedDstSizeAfterCopy: generationSize,
+			copySize:                 defaultCopySize,
+			expectedErrors: map[CopyRangeMethod]error{
+				CopyRangeMethodIoctl:            syscall.EINVAL,
+				CopyRangeMethodDuplicateExtents: syscall.EINVAL,
+			},
+		},
+		{
+			name:                     "aligned offsets unaligned size",
+			srcSize:                  generationSize,
+			dstSize:                  generationSize,
+			srcOffset:                0,
+			dstOffset:                0,
+			srcStartingPos:           0,
+			dstStartingPos:           0,
+			expectedDstSizeAfterCopy: generationSize,
+			copySize:                 defaultCopySize + 1,
+			expectedErrors: map[CopyRangeMethod]error{
+				CopyRangeMethodIoctl:            syscall.EINVAL,
+				CopyRangeMethodDuplicateExtents: syscall.EINVAL,
 			},
 		},
 		// Last block that starts on a nice boundary
@@ -189,131 +250,149 @@ var (
 	}
 )
 
-func TestCopyRange(ttt *testing.T) {
+func TestCopyRange(tttt *testing.T) {
 	randSrc := rand.New(rand.NewSource(rand.Int63()))
-	for copyMethod, impl := range copyRangeMethods {
+	paths := filepath.SplitList(os.Getenv("STFSTESTPATH"))
-		ttt.Run(copyMethod.String(), func(tt *testing.T) {
+	if len(paths) == 0 {
-			for _, testCase := range testCases {
+		paths = []string{""}
-				tt.Run(testCase.name, func(t *testing.T) {
+	}
-					srcBuf := make([]byte, testCase.srcSize)
+	for _, path := range paths {
-					dstBuf := make([]byte, testCase.dstSize)
+		testPath, err := ioutil.TempDir(path, "")
-					td, err := ioutil.TempDir(os.Getenv("STFSTESTPATH"), "")
+		if err != nil {
-					if err != nil {
+			tttt.Fatal(err)
-						t.Fatal(err)
+		}
-					}
+		defer os.RemoveAll(testPath)
-					defer func() { _ = os.RemoveAll(td) }()
+		name := path
-					fs := NewFilesystem(FilesystemTypeBasic, td)
+		if name == "" {
-
+			name = "tmp"
-					if _, err := io.ReadFull(randSrc, srcBuf); err != nil {
+		}
-						t.Fatal(err)
+		tttt.Run(name, func(ttt *testing.T) {
-					}
+			for copyMethod, impl := range copyRangeMethods {
-
+				ttt.Run(copyMethod.String(), func(tt *testing.T) {
-					if _, err := io.ReadFull(randSrc, dstBuf); err != nil {
+					for _, testCase := range testCases {
-						t.Fatal(err)
+						tt.Run(testCase.name, func(t *testing.T) {
-					}
+							srcBuf := make([]byte, testCase.srcSize)
-
+							dstBuf := make([]byte, testCase.dstSize)
-					src, err := fs.Create("src")
+							td, err := ioutil.TempDir(testPath, "")
-					if err != nil {
+							if err != nil {
-						t.Fatal(err)
+								t.Fatal(err)
-					}
-					defer func() { _ = src.Close() }()
-
-					dst, err := fs.Create("dst")
-					if err != nil {
-						t.Fatal(err)
-					}
-					defer func() { _ = dst.Close() }()
-
-					// Write some data
-
-					if _, err := src.Write(srcBuf); err != nil {
-						t.Fatal(err)
-					}
-
-					if _, err := dst.Write(dstBuf); err != nil {
-						t.Fatal(err)
-					}
-
-					// Set the offsets
-
-					if n, err := src.Seek(testCase.srcStartingPos, io.SeekStart); err != nil || n != testCase.srcStartingPos {
-						t.Fatal(err)
-					}
-
-					if n, err := dst.Seek(testCase.dstStartingPos, io.SeekStart); err != nil || n != testCase.dstStartingPos {
-						t.Fatal(err)
-					}
-
-					if err := impl(src.(basicFile), dst.(basicFile), testCase.srcOffset, testCase.dstOffset, testCase.copySize); err != nil {
-						if err == syscall.ENOTSUP {
-							// Test runner can adjust directory in which to run the tests, that allow broader tests.
-							t.Skip("Not supported on the current filesystem, set STFSTESTPATH env var.")
-						}
-						if testCase.expectedErrors[copyMethod] == err {
-							return
-						}
-						t.Fatal(err)
-					} else if testCase.expectedErrors[copyMethod] != nil {
-						t.Fatal("did not get expected error")
-					}
-
-					// Check offsets where we expect them
-
-					if srcCurPos, err := src.Seek(0, io.SeekCurrent); err != nil {
-						t.Fatal(err)
-					} else if srcCurPos != testCase.srcStartingPos {
-						t.Errorf("src pos expected %d got %d", testCase.srcStartingPos, srcCurPos)
-					}
-
-					if dstCurPos, err := dst.Seek(0, io.SeekCurrent); err != nil {
-						t.Fatal(err)
-					} else if dstCurPos != testCase.dstStartingPos {
-						t.Errorf("dst pos expected %d got %d", testCase.dstStartingPos, dstCurPos)
-					}
-
-					// Check dst size
-
-					if fi, err := dst.Stat(); err != nil {
-						t.Fatal(err)
-					} else if fi.Size() != testCase.expectedDstSizeAfterCopy {
-						t.Errorf("expected %d size, got %d", testCase.expectedDstSizeAfterCopy, fi.Size())
-					}
-
-					// Check the data is as expected
-
-					if _, err := dst.Seek(0, io.SeekStart); err != nil {
-						t.Fatal(err)
-					}
-
-					resultBuf := make([]byte, testCase.expectedDstSizeAfterCopy)
-					if _, err := io.ReadFull(dst, resultBuf); err != nil {
-						t.Fatal(err)
-					}
-
-					if !bytes.Equal(srcBuf[testCase.srcOffset:testCase.srcOffset+testCase.copySize], resultBuf[testCase.dstOffset:testCase.dstOffset+testCase.copySize]) {
-						t.Errorf("Not equal")
-					}
-
-					// Check not copied content does not get corrupted
-
-					if testCase.dstOffset > testCase.dstSize {
-						if !bytes.Equal(dstBuf[:testCase.dstSize], resultBuf[:testCase.dstSize]) {
-							t.Error("region before copy region not equals")
-						}
-						if !bytes.Equal(resultBuf[testCase.dstSize:testCase.dstOffset], make([]byte, testCase.dstOffset-testCase.dstSize)) {
-							t.Error("found non zeroes in expected zero region")
-						}
-					} else {
-						if !bytes.Equal(dstBuf[:testCase.dstOffset], resultBuf[:testCase.dstOffset]) {
-							t.Error("region before copy region not equals")
-						}
-						afterCopyStart := testCase.dstOffset + testCase.copySize
-
-						if afterCopyStart < testCase.dstSize {
-							if !bytes.Equal(dstBuf[afterCopyStart:], resultBuf[afterCopyStart:len(dstBuf)]) {
-								t.Error("region after copy region not equals")
 							}
-						}
+							defer os.RemoveAll(td)
+
+							fs := NewFilesystem(FilesystemTypeBasic, td)
+
+							if _, err := io.ReadFull(randSrc, srcBuf); err != nil {
+								t.Fatal(err)
+							}
+
+							if _, err := io.ReadFull(randSrc, dstBuf); err != nil {
+								t.Fatal(err)
+							}
+
+							src, err := fs.Create("src")
+							if err != nil {
+								t.Fatal(err)
+							}
+							defer func() { _ = src.Close() }()
+
+							dst, err := fs.Create("dst")
+							if err != nil {
+								t.Fatal(err)
+							}
+							defer func() { _ = dst.Close() }()
+
+							// Write some data
+
+							if _, err := src.Write(srcBuf); err != nil {
+								t.Fatal(err)
+							}
+
+							if _, err := dst.Write(dstBuf); err != nil {
+								t.Fatal(err)
+							}
+
+							// Set the offsets
+
+							if n, err := src.Seek(testCase.srcStartingPos, io.SeekStart); err != nil || n != testCase.srcStartingPos {
+								t.Fatal(err)
+							}
+
+							if n, err := dst.Seek(testCase.dstStartingPos, io.SeekStart); err != nil || n != testCase.dstStartingPos {
+								t.Fatal(err)
+							}
+
+							if err := impl(src.(basicFile), dst.(basicFile), testCase.srcOffset, testCase.dstOffset, testCase.copySize); err != nil {
+								if err == syscall.ENOTSUP {
+									// Test runner can adjust directory in which to run the tests, that allow broader tests.
+									t.Skip("Not supported on the current filesystem, set STFSTESTPATH env var.")
+								}
+								if testCase.expectedErrors[copyMethod] == err {
+									return
+								}
+								t.Fatal(err)
+							} else if testCase.expectedErrors[copyMethod] != nil {
+								t.Fatal("did not get expected error")
+							}
+
+							// Check offsets where we expect them
+
+							if srcCurPos, err := src.Seek(0, io.SeekCurrent); err != nil {
+								t.Fatal(err)
+							} else if srcCurPos != testCase.srcStartingPos {
+								t.Errorf("src pos expected %d got %d", testCase.srcStartingPos, srcCurPos)
+							}
+
+							if dstCurPos, err := dst.Seek(0, io.SeekCurrent); err != nil {
+								t.Fatal(err)
+							} else if dstCurPos != testCase.dstStartingPos {
+								t.Errorf("dst pos expected %d got %d", testCase.dstStartingPos, dstCurPos)
+							}
+
+							// Check dst size
+
+							if fi, err := dst.Stat(); err != nil {
+								t.Fatal(err)
+							} else if fi.Size() != testCase.expectedDstSizeAfterCopy {
+								t.Errorf("expected %d size, got %d", testCase.expectedDstSizeAfterCopy, fi.Size())
+							}
+
+							// Check the data is as expected
+
+							if _, err := dst.Seek(0, io.SeekStart); err != nil {
+								t.Fatal(err)
+							}
+
+							resultBuf := make([]byte, testCase.expectedDstSizeAfterCopy)
+							if _, err := io.ReadFull(dst, resultBuf); err != nil {
+								t.Fatal(err)
+							}
+
+							if !bytes.Equal(srcBuf[testCase.srcOffset:testCase.srcOffset+testCase.copySize], resultBuf[testCase.dstOffset:testCase.dstOffset+testCase.copySize]) {
+								t.Errorf("Not equal")
+							}
+
+							// Check not copied content does not get corrupted
+
+							if testCase.dstOffset > testCase.dstSize {
+								if !bytes.Equal(dstBuf[:testCase.dstSize], resultBuf[:testCase.dstSize]) {
+									t.Error("region before copy region not equals")
+								}
+								if !bytes.Equal(resultBuf[testCase.dstSize:testCase.dstOffset], make([]byte, testCase.dstOffset-testCase.dstSize)) {
+									t.Error("found non zeroes in expected zero region")
+								}
+							} else {
+								if !bytes.Equal(dstBuf[:testCase.dstOffset], resultBuf[:testCase.dstOffset]) {
+									t.Error("region before copy region not equals")
+								}
+								afterCopyStart := testCase.dstOffset + testCase.copySize
+
+								if afterCopyStart < testCase.dstSize {
+									if !bytes.Equal(dstBuf[afterCopyStart:], resultBuf[afterCopyStart:len(dstBuf)]) {
+										t.Error("region after copy region not equals")
+									}
+								}
+							}
+						})
 					}
 				})
 			}

lib/fs/mtimefs.go

@@ -130,7 +130,7 @@ func (f *MtimeFS) Create(name string) (File, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &mtimeFile{fd, f}, nil
+	return mtimeFile{fd, f}, nil
 }
 
 func (f *MtimeFS) Open(name string) (File, error) {
@@ -138,7 +138,7 @@ func (f *MtimeFS) Open(name string) (File, error) {
 	if err != nil {
 		return nil, err
 	}
-	return &mtimeFile{fd, f}, nil
+	return mtimeFile{fd, f}, nil
 }
 
 func (f *MtimeFS) OpenFile(name string, flags int, mode FileMode) (File, error) {
@@ -146,7 +146,7 @@ func (f *MtimeFS) OpenFile(name string, flags int, mode FileMode) (File, error)
 	if err != nil {
 		return nil, err
 	}
-	return &mtimeFile{fd, f}, nil
+	return mtimeFile{fd, f}, nil
 }
 
 // "real" is the on disk timestamp
@@ -208,7 +208,7 @@ type mtimeFile struct {
 	fs *MtimeFS
 }
 
-func (f *mtimeFile) Stat() (FileInfo, error) {
+func (f mtimeFile) Stat() (FileInfo, error) {
 	info, err := f.File.Stat()
 	if err != nil {
 		return nil, err
@@ -228,6 +228,10 @@ func (f *mtimeFile) Stat() (FileInfo, error) {
 	return info, nil
 }
 
+func (f mtimeFile) unwrap() File {
+	return f.File
+}
+
 // The dbMtime is our database representation
 
 type dbMtime struct {

lib/model/folder_sendrecv_test.go

@@ -205,7 +205,11 @@ func TestHandleFileWithTemp(t *testing.T) {
 }
 
 func TestCopierFinder(t *testing.T) {
-	for _, method := range []fs.CopyRangeMethod{fs.CopyRangeMethodStandard, fs.CopyRangeMethodAllWithFallback} {
+	methods := []fs.CopyRangeMethod{fs.CopyRangeMethodStandard, fs.CopyRangeMethodAllWithFallback}
+	if runtime.GOOS == "linux" {
+		methods = append(methods, fs.CopyRangeMethodSendFile)
+	}
+	for _, method := range methods {
 		t.Run(method.String(), func(t *testing.T) {
 			// After diff between required and existing we should:
 			// Copy: 1, 2, 3, 4, 6, 7, 8