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path: root/internal/fusefrontend/file2_allocate_truncate.go
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Diffstat (limited to 'internal/fusefrontend/file2_allocate_truncate.go')
-rw-r--r--internal/fusefrontend/file2_allocate_truncate.go217
1 files changed, 217 insertions, 0 deletions
diff --git a/internal/fusefrontend/file2_allocate_truncate.go b/internal/fusefrontend/file2_allocate_truncate.go
new file mode 100644
index 0000000..f799a3e
--- /dev/null
+++ b/internal/fusefrontend/file2_allocate_truncate.go
@@ -0,0 +1,217 @@
+package fusefrontend
+
+// FUSE operations Truncate and Allocate on file handles
+// i.e. ftruncate and fallocate
+
+import (
+ "log"
+ "syscall"
+
+ "github.com/hanwen/go-fuse/v2/fuse"
+
+ "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(off uint64, sz uint64, mode uint32) fuse.Status {
+ 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 fuse.Status(syscall.EOPNOTSUPP)
+ }
+
+ f.fdLock.RLock()
+ defer f.fdLock.RUnlock()
+ if f.released {
+ return fuse.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 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 *File2) 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.qIno.Ino, f.intFd())
+ return fuse.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 fuse.ToStatus(err)
+ }
+ // Truncate to zero kills the file header
+ f.fileTableEntry.ID = 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.qIno.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(nil, 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 *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) fuse.Status {
+ 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)
+ _, status := f.doWrite(buf, int64(newEOFOffset))
+ return status
+ }
+ }
+ // 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.
+ status := f.zeroPad(oldPlainSz)
+ if !status.Ok() {
+ return status
+ }
+ // 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 fuse.ToStatus(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 fuse.ToStatus(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)
+ _, status = f.doWrite(buf, int64(newEOFOffset))
+ return status
+}