209 lines
6.6 KiB
Go
209 lines
6.6 KiB
Go
package fusefrontend
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// FUSE operations Truncate and Allocate on file handles
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// i.e. ftruncate and fallocate
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import (
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"context"
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"log"
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"syscall"
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"github.com/hanwen/go-fuse/v2/fs"
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"github.com/rfjakob/gocryptfs/internal/syscallcompat"
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"github.com/rfjakob/gocryptfs/internal/tlog"
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)
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// Allocate - FUSE call for fallocate(2)
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//
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// mode=FALLOC_FL_KEEP_SIZE is implemented directly.
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//
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// mode=FALLOC_DEFAULT is implemented as a two-step process:
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//
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// (1) Allocate the space using FALLOC_FL_KEEP_SIZE
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// (2) Set the file size using ftruncate (via truncateGrowFile)
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//
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// This allows us to reuse the file grow mechanics from Truncate as they are
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// complicated and hard to get right.
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//
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// Other modes (hole punching, zeroing) are not supported.
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func (f *File2) Allocate(ctx context.Context, off uint64, sz uint64, mode uint32) syscall.Errno {
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if mode != FALLOC_DEFAULT && mode != FALLOC_FL_KEEP_SIZE {
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f := func() {
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tlog.Info.Printf("fallocate: only mode 0 (default) and 1 (keep size) are supported")
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}
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allocateWarnOnce.Do(f)
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return syscall.EOPNOTSUPP
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}
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f.fdLock.RLock()
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defer f.fdLock.RUnlock()
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if f.released {
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return syscall.EBADF
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}
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f.fileTableEntry.ContentLock.Lock()
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defer f.fileTableEntry.ContentLock.Unlock()
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blocks := f.contentEnc.ExplodePlainRange(off, sz)
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firstBlock := blocks[0]
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lastBlock := blocks[len(blocks)-1]
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// Step (1): Allocate the space the user wants using FALLOC_FL_KEEP_SIZE.
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// This will fill file holes and/or allocate additional space past the end of
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// the file.
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cipherOff := firstBlock.BlockCipherOff()
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cipherSz := lastBlock.BlockCipherOff() - cipherOff +
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f.contentEnc.BlockOverhead() + lastBlock.Skip + lastBlock.Length
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err := syscallcompat.Fallocate(f.intFd(), FALLOC_FL_KEEP_SIZE, int64(cipherOff), int64(cipherSz))
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tlog.Debug.Printf("Allocate off=%d sz=%d mode=%x cipherOff=%d cipherSz=%d\n",
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off, sz, mode, cipherOff, cipherSz)
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if err != nil {
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return fs.ToErrno(err)
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}
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if mode == FALLOC_FL_KEEP_SIZE {
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// The user did not want to change the apparent size. We are done.
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return 0
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}
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// Step (2): Grow the apparent file size
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// We need the old file size to determine if we are growing the file at all.
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newPlainSz := off + sz
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oldPlainSz, err := f.statPlainSize()
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if err != nil {
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return fs.ToErrno(err)
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}
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if newPlainSz <= oldPlainSz {
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// The new size is smaller (or equal). Fallocate with mode = 0 never
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// truncates a file, so we are done.
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return 0
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}
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// The file grows. The space has already been allocated in (1), so what is
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// left to do is to pad the first and last block and call truncate.
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// truncateGrowFile does just that.
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return f.truncateGrowFile(oldPlainSz, newPlainSz)
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}
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// truncate - called from Setattr.
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func (f *File2) truncate(newSize uint64) (errno syscall.Errno) {
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var err error
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// Common case first: Truncate to zero
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if newSize == 0 {
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err = syscall.Ftruncate(int(f.fd.Fd()), 0)
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if err != nil {
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tlog.Warn.Printf("ino%d fh%d: Ftruncate(fd, 0) returned error: %v", f.qIno.Ino, f.intFd(), err)
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return fs.ToErrno(err)
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}
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// Truncate to zero kills the file header
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f.fileTableEntry.ID = nil
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return 0
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}
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// We need the old file size to determine if we are growing or shrinking
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// the file
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oldSize, err := f.statPlainSize()
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if err != nil {
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return fs.ToErrno(err)
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}
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oldB := float32(oldSize) / float32(f.contentEnc.PlainBS())
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newB := float32(newSize) / float32(f.contentEnc.PlainBS())
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tlog.Debug.Printf("ino%d: FUSE Truncate from %.2f to %.2f blocks (%d to %d bytes)", f.qIno.Ino, oldB, newB, oldSize, newSize)
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// File size stays the same - nothing to do
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if newSize == oldSize {
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return 0
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}
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// File grows
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if newSize > oldSize {
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return f.truncateGrowFile(oldSize, newSize)
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}
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// File shrinks
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blockNo := f.contentEnc.PlainOffToBlockNo(newSize)
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cipherOff := f.contentEnc.BlockNoToCipherOff(blockNo)
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plainOff := f.contentEnc.BlockNoToPlainOff(blockNo)
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lastBlockLen := newSize - plainOff
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var data []byte
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if lastBlockLen > 0 {
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data, errno = f.doRead(nil, plainOff, lastBlockLen)
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if errno != 0 {
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tlog.Warn.Printf("Truncate: shrink doRead returned error: %v", err)
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return errno
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}
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}
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// Truncate down to the last complete block
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err = syscall.Ftruncate(int(f.fd.Fd()), int64(cipherOff))
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if err != nil {
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tlog.Warn.Printf("Truncate: shrink Ftruncate returned error: %v", err)
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return fs.ToErrno(err)
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}
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// Append partial block
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if lastBlockLen > 0 {
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_, status := f.doWrite(data, int64(plainOff))
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return status
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}
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return 0
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}
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// statPlainSize stats the file and returns the plaintext size
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func (f *File2) statPlainSize() (uint64, error) {
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fi, err := f.fd.Stat()
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if err != nil {
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tlog.Warn.Printf("ino%d fh%d: statPlainSize: %v", f.qIno.Ino, f.intFd(), err)
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return 0, err
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}
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cipherSz := uint64(fi.Size())
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plainSz := uint64(f.contentEnc.CipherSizeToPlainSize(cipherSz))
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return plainSz, nil
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}
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// truncateGrowFile extends a file using seeking or ftruncate performing RMW on
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// the first and last block as necessary. New blocks in the middle become
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// file holes unless they have been fallocate()'d beforehand.
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func (f *File2) truncateGrowFile(oldPlainSz uint64, newPlainSz uint64) syscall.Errno {
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if newPlainSz <= oldPlainSz {
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log.Panicf("BUG: newSize=%d <= oldSize=%d", newPlainSz, oldPlainSz)
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}
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newEOFOffset := newPlainSz - 1
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if oldPlainSz > 0 {
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n1 := f.contentEnc.PlainOffToBlockNo(oldPlainSz - 1)
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n2 := f.contentEnc.PlainOffToBlockNo(newEOFOffset)
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// The file is grown within one block, no need to pad anything.
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// Write a single zero to the last byte and let doWrite figure out the RMW.
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if n1 == n2 {
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buf := make([]byte, 1)
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_, errno := f.doWrite(buf, int64(newEOFOffset))
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return errno
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}
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}
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// The truncate creates at least one new block.
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//
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// Make sure the old last block is padded to the block boundary. This call
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// is a no-op if it is already block-aligned.
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errno := f.zeroPad(oldPlainSz)
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if errno != 0 {
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return errno
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}
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// The new size is block-aligned. In this case we can do everything ourselves
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// and avoid the call to doWrite.
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if newPlainSz%f.contentEnc.PlainBS() == 0 {
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// The file was empty, so it did not have a header. Create one.
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if oldPlainSz == 0 {
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id, err := f.createHeader()
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if err != nil {
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return fs.ToErrno(err)
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}
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f.fileTableEntry.ID = id
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}
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cSz := int64(f.contentEnc.PlainSizeToCipherSize(newPlainSz))
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err := syscall.Ftruncate(f.intFd(), cSz)
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if err != nil {
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tlog.Warn.Printf("Truncate: grow Ftruncate returned error: %v", err)
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}
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return fs.ToErrno(err)
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}
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// The new size is NOT aligned, so we need to write a partial block.
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// Write a single zero to the last byte and let doWrite figure it out.
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buf := make([]byte, 1)
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_, errno = f.doWrite(buf, int64(newEOFOffset))
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return errno
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}
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