From f6e2ba95fd384e5ab47deb288446058c3f97a850 Mon Sep 17 00:00:00 2001
From: Han-Wen Nienhuys <hanwen@google.com>
Date: Thu, 10 Mar 2011 19:37:08 -0300
Subject: [PATCH] Fix mount raciness.
---
fuse/loopback_test.go | 2 +-
fuse/pathfilesystem.go | 61 +++++++++++++++++++++++++++++-------------
2 files changed, 43 insertions(+), 20 deletions(-)
diff --git a/fuse/loopback_test.go b/fuse/loopback_test.go
index 69fde00..8314205 100644
--- a/fuse/loopback_test.go
+++ b/fuse/loopback_test.go
@@ -559,7 +559,7 @@ func TestRecursiveMount(t *testing.T) {
f.Close()
- // The close takes some time to propagate through
+ log.Println("Waiting for kernel to flush file-close to fuse...")
time.Sleep(1e9)
code = ts.connector.Unmount("/mnt")
diff --git a/fuse/pathfilesystem.go b/fuse/pathfilesystem.go
index 84ecea2..9e18335 100644
--- a/fuse/pathfilesystem.go
+++ b/fuse/pathfilesystem.go
@@ -2,23 +2,33 @@ package fuse
import (
"bytes"
- "sync"
"fmt"
"log"
"path"
"strings"
+ "sync"
)
type mountData struct {
// If non-nil the file system mounted here.
fs PathFilesystem
+ // Protects the variables below.
+ mutex sync.RWMutex
+
// If yes, we are looking to unmount the mounted fs.
unmountPending bool
- openFiles int
- openDirs int
- subMounts int
+ // Count files, dirs and mounts.
+ openCount int
+}
+
+// TODO - should we call async or not? what is the goroutine creation
+// overhead vs. lock acquisition.
+func (me *mountData) incOpenCount(delta int) {
+ me.mutex.Lock()
+ defer me.mutex.Unlock()
+ me.openCount += delta
}
func newMount(fs PathFilesystem) *mountData {
@@ -66,12 +76,15 @@ func (me *inodeData) GetPath() (path string, mount *mountData) {
if inode == nil {
panic("did not find parent with mount")
}
-
- fullPath := strings.Join(components[j:], "/")
mount = inode.mount
+
+ mount.mutex.RLock()
+ defer mount.mutex.RUnlock()
if mount.unmountPending {
- mount = nil
+ return "", nil
}
+
+ fullPath := strings.Join(components[j:], "/")
return fullPath, mount
}
@@ -193,6 +206,12 @@ func (me *PathFileSystemConnector) forgetUpdate(nodeId uint64, forgetCount int)
data, ok := me.inodePathMapByInode[nodeId]
if ok {
data.LookupCount -= forgetCount
+
+ if data.mount != nil {
+ data.mount.mutex.RLock()
+ defer data.mount.mutex.RUnlock()
+ }
+
if data.LookupCount <= 0 && data.RefCount <= 0 && (data.mount == nil || data.mount.unmountPending) {
me.inodePathMap[data.Key()] = nil, false
}
@@ -344,11 +363,10 @@ func (me *PathFileSystemConnector) Mount(mountPoint string, fs PathFilesystem) S
log.Println("Mount: ", fs, "on", mountPoint, node)
}
- // TODO - this is technically a race-condition?
node.mount = newMount(fs)
if node.Parent != nil {
_, parentMount := node.Parent.GetPath()
- parentMount.subMounts++
+ parentMount.incOpenCount(1)
}
return OK
@@ -365,7 +383,9 @@ func (me *PathFileSystemConnector) Unmount(path string) Status {
panic(path)
}
- if mount.openFiles+mount.openDirs+mount.subMounts > 0 {
+ mount.mutex.Lock()
+ defer mount.mutex.Unlock()
+ if mount.openCount > 0 {
log.Println("busy: ", mount)
return EBUSY
}
@@ -373,7 +393,7 @@ func (me *PathFileSystemConnector) Unmount(path string) Status {
if me.Debug {
log.Println("Unmount: ", mount)
}
- // node manipulations are racy?
+
if node.RefCount > 0 {
mount.fs.Unmount()
mount.unmountPending = true
@@ -383,7 +403,7 @@ func (me *PathFileSystemConnector) Unmount(path string) Status {
if node.Parent != nil {
_, parentMount := node.Parent.GetPath()
- parentMount.subMounts--
+ parentMount.incOpenCount(-1)
}
return OK
}
@@ -476,8 +496,7 @@ func (me *PathFileSystemConnector) OpenDir(header *InHeader, input *OpenIn) (fla
return 0, nil, err
}
- // TODO - racy?
- mount.openDirs++
+ mount.incOpenCount(1)
de := new(FuseDir)
de.connector = me
@@ -497,8 +516,7 @@ func (me *PathFileSystemConnector) Open(header *InHeader, input *OpenIn) (flags
return 0, nil, err
}
- // TODO - racy?
- mount.openFiles++
+ mount.incOpenCount(1)
return 0, f, OK
}
@@ -678,19 +696,24 @@ func (me *PathFileSystemConnector) Create(header *InHeader, input *CreateIn, nam
return 0, nil, nil, err
}
- mount.openFiles++
+ mount.incOpenCount(1)
+
out, code = me.Lookup(header, name)
return 0, f, out, code
}
func (me *PathFileSystemConnector) Release(header *InHeader, f RawFuseFile) {
_, mount := me.GetPath(header.NodeId)
- mount.openFiles--
+ if mount != nil {
+ mount.incOpenCount(-1)
+ }
}
func (me *PathFileSystemConnector) ReleaseDir(header *InHeader, f RawFuseDir) {
_, mount := me.GetPath(header.NodeId)
- mount.openDirs--
+ if mount != nil {
+ mount.incOpenCount(-1)
+ }
}
////////////////////////////////////////////////////////////////
--
2.30.9