fusefronted: move Truncate() and Allocate() to their own file

These are large complicated implementations that will share some
code.

1 files changed, 123 insertions, 0 deletions

diff --git a/internal/fusefrontend/file_allocate_truncate.go b/internal/fusefrontend/file_allocate_truncate.go
new file mode 100644
index 0000000..5be7df4
--- /dev/null
+++ b/internal/fusefrontend/file_allocate_truncate.go
@@ -0,0 +1,123 @@
+package fusefrontend
+
+// FUSE operations Truncate and Allocate on file handles
+// i.e. ftruncate and fallocate
+
+import (
+	"sync"
+	"syscall"
+
+	"github.com/hanwen/go-fuse/fuse"
+
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+// Only warn once
+var allocateWarnOnce sync.Once
+
+// Allocate - FUSE call, fallocate(2)
+// This is not implemented yet in gocryptfs, but it is neither in EncFS. This
+// suggests that the user demand is low.
+func (f *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status {
+	allocateWarnOnce.Do(func() {
+		tlog.Warn.Printf("fallocate(2) is not supported, returning ENOSYS - see https://github.com/rfjakob/gocryptfs/issues/1")
+	})
+	return fuse.ENOSYS
+}
+
+// Truncate - FUSE call
+func (f *file) Truncate(newSize uint64) fuse.Status {
+	f.fdLock.RLock()
+	defer f.fdLock.RUnlock()
+	if f.released {
+		// The file descriptor has been closed concurrently.
+		tlog.Warn.Printf("ino%d fh%d: Truncate on released file", f.ino, f.intFd())
+		return fuse.EBADF
+	}
+	wlock.lock(f.ino)
+	defer wlock.unlock(f.ino)
+	var err error
+	// Common case first: Truncate to zero
+	if newSize == 0 {
+		err = syscall.Ftruncate(int(f.fd.Fd()), 0)
+		if err != nil {
+			tlog.Warn.Printf("ino%d fh%d: Ftruncate(fd, 0) returned error: %v", f.ino, f.intFd(), err)
+			return fuse.ToStatus(err)
+		}
+		// Truncate to zero kills the file header
+		f.header = nil
+		return fuse.OK
+	}
+	// We need the old file size to determine if we are growing or shrinking
+	// the file
+	fi, err := f.fd.Stat()
+	if err != nil {
+		tlog.Warn.Printf("ino%d fh%d: Truncate: Fstat failed: %v", f.ino, f.intFd(), err)
+		return fuse.ToStatus(err)
+	}
+	oldSize := f.contentEnc.CipherSizeToPlainSize(uint64(fi.Size()))
+	{
+		oldB := float32(oldSize) / float32(f.contentEnc.PlainBS())
+		newB := float32(newSize) / float32(f.contentEnc.PlainBS())
+		tlog.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)", f.ino, oldB, newB, oldSize, newSize)
+	}
+	// File size stays the same - nothing to do
+	if newSize == oldSize {
+		return fuse.OK
+	}
+	// File grows
+	if newSize > oldSize {
+		// File was empty, create new header
+		if oldSize == 0 {
+			err = f.createHeader()
+			if err != nil {
+				return fuse.ToStatus(err)
+			}
+		}
+		// New blocks to add
+		addBlocks := f.contentEnc.ExplodePlainRange(oldSize, newSize-oldSize)
+		if len(addBlocks) >= 2 {
+			f.zeroPad(oldSize)
+		}
+		lastBlock := addBlocks[len(addBlocks)-1]
+		if lastBlock.IsPartial() {
+			off := lastBlock.BlockPlainOff()
+			_, status := f.doWrite(make([]byte, lastBlock.Length), int64(off+lastBlock.Skip))
+			return status
+		} else {
+			off := lastBlock.BlockCipherOff()
+			err = syscall.Ftruncate(f.intFd(), int64(off+f.contentEnc.CipherBS()))
+			if err != nil {
+				tlog.Warn.Printf("Truncate: grow Ftruncate returned error: %v", err)
+			}
+			return fuse.ToStatus(err)
+		}
+	} else {
+		// File shrinks
+		blockNo := f.contentEnc.PlainOffToBlockNo(newSize)
+		cipherOff := f.contentEnc.BlockNoToCipherOff(blockNo)
+		plainOff := f.contentEnc.BlockNoToPlainOff(blockNo)
+		lastBlockLen := newSize - plainOff
+		var data []byte
+		if lastBlockLen > 0 {
+			var status fuse.Status
+			data, status = f.doRead(plainOff, lastBlockLen)
+			if status != fuse.OK {
+				tlog.Warn.Printf("Truncate: shrink doRead returned error: %v", err)
+				return status
+			}
+		}
+		// Truncate down to the last complete block
+		err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
+		if err != nil {
+			tlog.Warn.Printf("Truncate: shrink Ftruncate returned error: %v", err)
+			return fuse.ToStatus(err)
+		}
+		// Append partial block
+		if lastBlockLen > 0 {
+			_, status := f.doWrite(data, int64(plainOff))
+			return status
+		}
+		return fuse.OK
+	}
+}