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package fusefrontend
// FUSE operations Truncate and Allocate on file handles
// i.e. ftruncate and fallocate
import (
"context"
"log"
"sync"
"syscall"
"github.com/hanwen/go-fuse/v2/fs"
"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(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 *File) truncate(newSize uint64) (errno syscall.Errno) {
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 *File) 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 *File) 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
}
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