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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/tlog"
)
const FALLOC_DEFAULT = 0x00
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.ino)
defer wlock.unlock(f.ino)
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 := syscall.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.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
oldSize, err := f.statPlainSize()
if err != nil {
return fuse.ToStatus(err)
} else {
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 {
return f.truncateGrowFile(oldSize, newSize)
} 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
}
}
// 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.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 neccessary. 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
} 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)
}
}
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