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-rw-r--r--pathfs_frontend/file.go26
-rw-r--r--pathfs_frontend/write_lock.go66
2 files changed, 77 insertions, 15 deletions
diff --git a/pathfs_frontend/file.go b/pathfs_frontend/file.go
index 4639157..522b9c1 100644
--- a/pathfs_frontend/file.go
+++ b/pathfs_frontend/file.go
@@ -43,6 +43,7 @@ type file struct {
func NewFile(fd *os.File, writeOnly bool, cfs *cryptfs.CryptFS) nodefs.File {
var st syscall.Stat_t
syscall.Fstat(int(fd.Fd()), &st)
+ wlock.register(st.Ino)
return &file{
fd: fd,
@@ -59,20 +60,6 @@ func (f *file) InnerFile() nodefs.File {
func (f *file) SetInode(n *nodefs.Inode) {
}
-// Ensure that all modifications to the file contents are serialized and no
-// reads happen concurrently.
-//
-// This prevents several races:
-// * getFileId vs Truncate
-// * zeroPad vs Read
-// * RMW vs Write
-func (f *file) wlock() {
-}
-func (f *file) rlock() {
-}
-func (f *file) unlock() {
-}
-
// readHeader - load the file header from disk
//
// Returns io.EOF if the file is empty
@@ -252,6 +239,7 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
cryptfs.Debug.Printf("len(oldData)=%d len(blockData)=%d", len(oldData), len(blockData))
}
+ // Encrypt
blockOffset, blockLen := b.CiphertextRange()
blockData = f.cfs.EncryptBlock(blockData, b.BlockNo, f.header.Id)
cryptfs.Debug.Printf("ino%d: Writing %d bytes to block #%d",
@@ -271,6 +259,7 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
f.fdLock.Lock()
_, err = f.fd.WriteAt(blockData, int64(blockOffset))
f.fdLock.Unlock()
+
if err != nil {
cryptfs.Warn.Printf("doWrite: Write failed: %s", err.Error())
status = fuse.ToStatus(err)
@@ -284,6 +273,8 @@ func (f *file) doWrite(data []byte, off int64) (uint32, fuse.Status) {
// Write - FUSE call
func (f *file) Write(data []byte, off int64) (uint32, fuse.Status) {
cryptfs.Debug.Printf("ino%d: FUSE Write: offset=%d length=%d", f.ino, off, len(data))
+ wlock.lock(f.ino)
+ defer wlock.unlock(f.ino)
fi, err := f.fd.Stat()
if err != nil {
@@ -306,6 +297,7 @@ func (f *file) Release() {
f.fdLock.Lock()
f.fd.Close()
f.fdLock.Unlock()
+ wlock.unregister(f.ino)
}
// Flush - FUSE call
@@ -333,7 +325,11 @@ func (f *file) Fsync(flags int) (code fuse.Status) {
return r
}
+// Truncate - FUSE call
func (f *file) Truncate(newSize uint64) fuse.Status {
+ wlock.lock(f.ino)
+ defer wlock.unlock(f.ino)
+
// Common case first: Truncate to zero
if newSize == 0 {
f.fdLock.Lock()
@@ -343,7 +339,7 @@ func (f *file) Truncate(newSize uint64) fuse.Status {
cryptfs.Warn.Printf("Ftruncate(fd, 0) returned error: %v", err)
return fuse.ToStatus(err)
}
- // A truncate to zero kills the file header
+ // Truncate to zero kills the file header
f.header = nil
return fuse.OK
}
diff --git a/pathfs_frontend/write_lock.go b/pathfs_frontend/write_lock.go
new file mode 100644
index 0000000..0704eb6
--- /dev/null
+++ b/pathfs_frontend/write_lock.go
@@ -0,0 +1,66 @@
+package pathfs_frontend
+
+import (
+ "sync"
+)
+
+func init() {
+ wlock.m = make(map[uint64]*refCntMutex)
+}
+
+// wlock - serializes write accesses to each file (identified by inode number)
+// Writing partial blocks means we have to do read-modify-write cycles. We
+// really don't want concurrent writes there.
+// Concurrent full-block writes could actually be allowed, but are not to
+// keep the locking simple.
+var wlock wlockMap
+
+// wlockMap - usage:
+// 1) register
+// 2) lock ... unlock ...
+// 3) unregister
+type wlockMap struct {
+ mapMutex sync.RWMutex
+ m map[uint64]*refCntMutex
+}
+
+func (w *wlockMap) register(ino uint64) {
+ w.mapMutex.Lock()
+ r := w.m[ino]
+ if r == nil {
+ r = &refCntMutex{}
+ w.m[ino] = r
+ }
+ r.refCnt++ // this must happen inside the mapMutex lock
+ w.mapMutex.Unlock()
+}
+
+func (w *wlockMap) unregister(ino uint64) {
+ w.mapMutex.Lock()
+ r := w.m[ino]
+ r.refCnt--
+ if r.refCnt == 0 {
+ delete(w.m, ino)
+ }
+ w.mapMutex.Unlock()
+}
+
+func (w *wlockMap) lock(ino uint64) {
+ w.mapMutex.RLock()
+ r := w.m[ino]
+ w.mapMutex.RUnlock()
+ r.Lock() // this can take a long time - execute outside the mapMutex lock
+}
+
+func (w *wlockMap) unlock(ino uint64) {
+ w.mapMutex.RLock()
+ r := w.m[ino]
+ w.mapMutex.RUnlock()
+ r.Unlock()
+}
+
+// refCntMutex - mutex with reference count
+type refCntMutex struct {
+ sync.Mutex
+ refCnt int
+}