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// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package model
import (
"encoding/binary"
"fmt"
"io"
"time"
"github.com/syncthing/syncthing/lib/fs"
"github.com/syncthing/syncthing/lib/osutil"
"github.com/syncthing/syncthing/lib/protocol"
"github.com/syncthing/syncthing/lib/sync"
)
// A sharedPullerState is kept for each file that is being synced and is kept
// updated along the way.
type sharedPullerState struct {
// Immutable, does not require locking
file protocol.FileInfo // The new file (desired end state)
fs fs.Filesystem
folder string
tempName string
realName string
reused int // Number of blocks reused from temporary file
ignorePerms bool
hasCurFile bool // Whether curFile is set
curFile protocol.FileInfo // The file as it exists now in our database
sparse bool
created time.Time
fsync bool
// Mutable, must be locked for access
err error // The first error we hit
writer *lockedWriterAt // Wraps fd to prevent fd closing at the same time as writing
copyTotal int // Total number of copy actions for the whole job
pullTotal int // Total number of pull actions for the whole job
copyOrigin int // Number of blocks copied from the original file
copyOriginShifted int // Number of blocks copied from the original file but shifted
copyNeeded int // Number of copy actions still pending
pullNeeded int // Number of block pulls still pending
updated time.Time // Time when any of the counters above were last updated
closed bool // True if the file has been finalClosed.
available []int // Indexes of the blocks that are available in the temporary file
availableUpdated time.Time // Time when list of available blocks was last updated
mut sync.RWMutex // Protects the above
}
func newSharedPullerState(file protocol.FileInfo, fs fs.Filesystem, folderID, tempName string, blocks []protocol.BlockInfo, reused []int, ignorePerms, hasCurFile bool, curFile protocol.FileInfo, sparse bool, fsync bool) *sharedPullerState {
return &sharedPullerState{
file: file,
fs: fs,
folder: folderID,
tempName: tempName,
realName: file.Name,
copyTotal: len(blocks),
copyNeeded: len(blocks),
reused: len(reused),
updated: time.Now(),
available: reused,
availableUpdated: time.Now(),
ignorePerms: ignorePerms,
hasCurFile: hasCurFile,
curFile: curFile,
mut: sync.NewRWMutex(),
sparse: sparse,
fsync: fsync,
created: time.Now(),
}
}
// A momentary state representing the progress of the puller
type pullerProgress struct {
Total int `json:"total"`
Reused int `json:"reused"`
CopiedFromOrigin int `json:"copiedFromOrigin"`
CopiedFromOriginShifted int `json:"copiedFromOriginShifted"`
CopiedFromElsewhere int `json:"copiedFromElsewhere"`
Pulled int `json:"pulled"`
Pulling int `json:"pulling"`
BytesDone int64 `json:"bytesDone"`
BytesTotal int64 `json:"bytesTotal"`
}
// lockedWriterAt adds a lock to protect from closing the fd at the same time as writing.
// WriteAt() is goroutine safe by itself, but not against for example Close().
type lockedWriterAt struct {
mut sync.RWMutex
fd fs.File
}
// WriteAt itself is goroutine safe, thus just needs to acquire a read-lock to
// prevent closing concurrently (see SyncClose).
func (w *lockedWriterAt) WriteAt(p []byte, off int64) (n int, err error) {
w.mut.RLock()
defer w.mut.RUnlock()
return w.fd.WriteAt(p, off)
}
// SyncClose ensures that no more writes are happening before going ahead and
// syncing and closing the fd, thus needs to acquire a write-lock.
func (w *lockedWriterAt) SyncClose(fsync bool) error {
w.mut.Lock()
defer w.mut.Unlock()
if fsync {
if err := w.fd.Sync(); err != nil {
// Sync() is nice if it works but not worth failing the
// operation over if it fails.
l.Debugf("fsync failed: %v", err)
}
}
return w.fd.Close()
}
// tempFile returns the fd for the temporary file, reusing an open fd
// or creating the file as necessary.
func (s *sharedPullerState) tempFile() (*lockedWriterAt, error) {
s.mut.Lock()
defer s.mut.Unlock()
// If we've already hit an error, return early
if s.err != nil {
return nil, s.err
}
// If the temp file is already open, return the file descriptor
if s.writer != nil {
return s.writer, nil
}
if err := s.addWriterLocked(); err != nil {
s.failLocked(err)
return nil, err
}
return s.writer, nil
}
func (s *sharedPullerState) addWriterLocked() error {
return inWritableDir(s.tempFileInWritableDir, s.fs, s.tempName, s.ignorePerms)
}
// tempFileInWritableDir should only be called from tempFile.
func (s *sharedPullerState) tempFileInWritableDir(_ string) error {
// The permissions to use for the temporary file should be those of the
// final file, except we need user read & write at minimum. The
// permissions will be set to the final value later, but in the meantime
// we don't want to have a temporary file with looser permissions than
// the final outcome.
mode := fs.FileMode(s.file.Permissions) | 0600
if s.ignorePerms {
// When ignorePerms is set we use a very permissive mode and let the
// system umask filter it.
mode = 0666
}
// Attempt to create the temp file
// RDWR because of issue #2994.
flags := fs.OptReadWrite
if s.reused == 0 {
flags |= fs.OptCreate | fs.OptExclusive
} else if !s.ignorePerms {
// With sufficiently bad luck when exiting or crashing, we may have
// had time to chmod the temp file to read only state but not yet
// moved it to its final name. This leaves us with a read only temp
// file that we're going to try to reuse. To handle that, we need to
// make sure we have write permissions on the file before opening it.
//
// When ignorePerms is set we trust that the permissions are fine
// already and make no modification, as we would otherwise override
// what the umask dictates.
if err := s.fs.Chmod(s.tempName, mode); err != nil {
return fmt.Errorf("setting perms on temp file: %w", err)
}
}
fd, err := s.fs.OpenFile(s.tempName, flags, mode)
if err != nil {
return fmt.Errorf("opening temp file: %w", err)
}
// Hide the temporary file
s.fs.Hide(s.tempName)
// Don't truncate symlink files, as that will mean that the path will
// contain a bunch of nulls.
if s.sparse && !s.file.IsSymlink() {
size := s.file.Size
// Trailer added to encrypted files
if len(s.file.Encrypted) > 0 {
size += encryptionTrailerSize(s.file)
}
// Truncate sets the size of the file. This creates a sparse file or a
// space reservation, depending on the underlying filesystem.
if err := fd.Truncate(size); err != nil {
// The truncate call failed. That can happen in some cases when
// space reservation isn't possible or over some network
// filesystems... This generally doesn't matter.
if s.reused > 0 {
// ... but if we are attempting to reuse a file we have a
// corner case when the old file is larger than the new one
// and we can't just overwrite blocks and let the old data
// linger at the end. In this case we attempt a delete of
// the file and hope for better luck next time, when we
// should come around with s.reused == 0.
fd.Close()
if remErr := s.fs.Remove(s.tempName); remErr != nil {
l.Debugln("failed to remove temporary file:", remErr)
}
return err
}
}
}
// Same fd will be used by all writers
s.writer
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