package fusefrontend // FUSE operations Truncate and Allocate on file handles // i.e. ftruncate and fallocate import ( "context" "log" "syscall" "github.com/hanwen/go-fuse/v2/fs" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) // Allocate - FUSE call for fallocate(2) // // mode=FALLOC_FL_KEEP_SIZE is implemented directly. // // mode=FALLOC_DEFAULT is implemented as a two-step process: // // (1) Allocate the space using FALLOC_FL_KEEP_SIZE // (2) Set the file size using ftruncate (via truncateGrowFile) // // This allows us to reuse the file grow mechanics from Truncate as they are // complicated and hard to get right. // // Other modes (hole punching, zeroing) are not supported. func (f *File2) Allocate(ctx context.Context, off uint64, sz uint64, mode uint32) syscall.Errno { if mode != FALLOC_DEFAULT && mode != FALLOC_FL_KEEP_SIZE { f := func() { tlog.Info.Printf("fallocate: only mode 0 (default) and 1 (keep size) are supported") } allocateWarnOnce.Do(f) return syscall.EOPNOTSUPP } f.fdLock.RLock() defer f.fdLock.RUnlock() if f.released { return syscall.EBADF } f.fileTableEntry.ContentLock.Lock() defer f.fileTableEntry.ContentLock.Unlock() blocks := f.contentEnc.ExplodePlainRange(off, sz) firstBlock := blocks[0] lastBlock := blocks[len(blocks)-1] // Step (1): Allocate the space the user wants using FALLOC_FL_KEEP_SIZE. // This will fill file holes and/or allocate additional space past the end of // the file. cipherOff := firstBlock.BlockCipherOff() cipherSz := lastBlock.BlockCipherOff() - cipherOff + f.contentEnc.BlockOverhead() + lastBlock.Skip + lastBlock.Length err := syscallcompat.Fallocate(f.intFd(), FALLOC_FL_KEEP_SIZE, int64(cipherOff), int64(cipherSz)) tlog.Debug.Printf("Allocate off=%d sz=%d mode=%x cipherOff=%d cipherSz=%d\n", off, sz, mode, cipherOff, cipherSz) if err != nil { return fs.ToErrno(err) } if mode == FALLOC_FL_KEEP_SIZE { // The user did not want to change the apparent size. We are done. return 0 } // Step (2): Grow the apparent file size // We need the old file size to determine if we are growing the file at all. newPlainSz := off + sz oldPlainSz, err := f.statPlainSize() if err != nil { return fs.ToErrno(err) } if newPlainSz <= oldPlainSz { // The new size is smaller (or equal). Fallocate with mode = 0 never // truncates a file, so we are done. return 0 } // The file grows. The space has already been allocated in (1), so what is // left to do is to pad the first and last block and call truncate. // truncateGrowFile does just that. return f.truncateGrowFile(oldPlainSz, newPlainSz) } // truncate - called from Setattr. func (f *File2) truncate(newSize uint64) (errno syscall.Errno) { 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.qIno.Ino, f.intFd()) return syscall.EBADF } f.fileTableEntry.ContentLock.Lock() defer f.fileTableEntry.ContentLock.Unlock() 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.qIno.Ino, f.intFd(), err) return fs.ToErrno(err) } // Truncate to zero kills the file header f.fileTableEntry.ID = nil return 0 } // We need the old file size to determine if we are growing or shrinking // the file oldSize, err := f.statPlainSize() if err != nil { return fs.ToErrno(err) } 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.qIno.Ino, oldB, newB, oldSize, newSize) // File size stays the same - nothing to do if newSize == oldSize { return 0 } // File grows if newSize > oldSize { return f.truncateGrowFile(oldSize, newSize) } // 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 { data, errno = f.doRead(nil, plainOff, lastBlockLen) if errno != 0 { tlog.Warn.Printf("Truncate: shrink doRead returned error: %v", err) return errno } } // 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 fs.ToErrno(err) } // Append partial block if lastBlockLen > 0 { _, status := f.doWrite(data, int64(plainOff)) return status } return 0 } // statPlainSize stats the file and returns the plaintext size func (f *File2) statPlainSize() (uint64, error) { fi, err := f.fd.Stat() if err != nil { tlog.Warn.Printf("ino%d fh%d: statPlainSize: %v", f.qIno.Ino, f.intFd(), err) return 0, err } cipherSz := uint64(fi.Size()) plainSz := uint64(f.contentEnc.CipherSizeToPlainSize(cipherSz)) return plainSz, nil } // truncateGrowFile extends a file using seeking or ftruncate performing RMW on // the first and last block as necessary. New blocks in the middle become // file holes unless they have been fallocate()'d beforehand. func (f *File2) truncateGrowFile(oldPlainSz uint64, newPlainSz uint64) syscall.Errno { if newPlainSz <= oldPlainSz { log.Panicf("BUG: newSize=%d <= oldSize=%d", newPlainSz, oldPlainSz) } newEOFOffset := newPlainSz - 1 if oldPlainSz > 0 { n1 := f.contentEnc.PlainOffToBlockNo(oldPlainSz - 1) n2 := f.contentEnc.PlainOffToBlockNo(newEOFOffset) // The file is grown within one block, no need to pad anything. // Write a single zero to the last byte and let doWrite figure out the RMW. if n1 == n2 { buf := make([]byte, 1) _, errno := f.doWrite(buf, int64(newEOFOffset)) return errno } } // The truncate creates at least one new block. // // Make sure the old last block is padded to the block boundary. This call // is a no-op if it is already block-aligned. errno := f.zeroPad(oldPlainSz) if errno != 0 { return errno } // The new size is block-aligned. In this case we can do everything ourselves // and avoid the call to doWrite. if newPlainSz%f.contentEnc.PlainBS() == 0 { // The file was empty, so it did not have a header. Create one. if oldPlainSz == 0 { id, err := f.createHeader() if err != nil { return fs.ToErrno(err) } f.fileTableEntry.ID = id } cSz := int64(f.contentEnc.PlainSizeToCipherSize(newPlainSz)) err := syscall.Ftruncate(f.intFd(), cSz) if err != nil { tlog.Warn.Printf("Truncate: grow Ftruncate returned error: %v", err) } return fs.ToErrno(err) } // The new size is NOT aligned, so we need to write a partial block. // Write a single zero to the last byte and let doWrite figure it out. buf := make([]byte, 1) _, errno = f.doWrite(buf, int64(newEOFOffset)) return errno }