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

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