package fusefrontend // FUSE operations Truncate and Allocate on file handles // i.e. ftruncate and fallocate import ( "log" "sync" "syscall" "github.com/hanwen/go-fuse/fuse" "github.com/rfjakob/gocryptfs/internal/syscallcompat" "github.com/rfjakob/gocryptfs/internal/tlog" ) // FALLOC_DEFAULT is a "normal" fallocate operation const FALLOC_DEFAULT = 0x00 // FALLOC_FL_KEEP_SIZE allocates disk space while not modifying the file size const FALLOC_FL_KEEP_SIZE = 0x01 // Only warn once var allocateWarnOnce sync.Once // 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 *file) Allocate(off uint64, sz uint64, mode uint32) fuse.Status { if mode != FALLOC_DEFAULT && mode != FALLOC_FL_KEEP_SIZE { f := func() { tlog.Warn.Print("fallocate: only mode 0 (default) and 1 (keep size) are supported") } allocateWarnOnce.Do(f) return fuse.Status(syscall.EOPNOTSUPP) } f.fdLock.RLock() defer f.fdLock.RUnlock() if f.released { return fuse.EBADF } wlock.lock(f.devIno) defer wlock.unlock(f.devIno) 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.PlainSizeToCipherSize(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 fuse.ToStatus(err) } if mode == FALLOC_FL_KEEP_SIZE { // The user did not want to change the apparent size. We are done. return fuse.OK } // 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 fuse.ToStatus(err) } if newPlainSz <= oldPlainSz { // The new size is smaller (or equal). Fallocate with mode = 0 never // truncates a file, so we are done. return fuse.OK } // 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 - 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.devIno.ino, f.intFd()) return fuse.EBADF } wlock.lock(f.devIno) defer wlock.unlock(f.devIno) 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.devIno.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 oldSize, err := f.statPlainSize() if err != nil { return fuse.ToStatus(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.devIno.ino, oldB, newB, oldSize, newSize) // File size stays the same - nothing to do if newSize == oldSize { return fuse.OK } // 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 { 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 } // statPlainSize stats the file and returns the plaintext size func (f *file) statPlainSize() (uint64, error) { fi, err := f.fd.Stat() if err != nil { tlog.Warn.Printf("ino%d fh%d: statPlainSize: %v", f.devIno.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 *file) truncateGrowFile(oldPlainSz uint64, newPlainSz uint64) fuse.Status { if newPlainSz <= oldPlainSz { log.Panicf("BUG: newSize=%d <= oldSize=%d", newPlainSz, oldPlainSz) } var err error // File was empty, create new header if oldPlainSz == 0 { err = f.createHeader() if err != nil { return fuse.ToStatus(err) } } // New blocks to add addBlocks := f.contentEnc.ExplodePlainRange(oldPlainSz, newPlainSz-oldPlainSz) if oldPlainSz > 0 && len(addBlocks) >= 2 { // Zero-pad the first block (unless the first block is also the last block) f.zeroPad(oldPlainSz) } lastBlock := addBlocks[len(addBlocks)-1] if lastBlock.IsPartial() { // Write at the new end of the file. The seek implicitly grows the file // (creates a file hole) and doWrite() takes care of RMW. off := lastBlock.BlockPlainOff() _, status := f.doWrite(make([]byte, lastBlock.Length), int64(off+lastBlock.Skip)) return status } 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) }