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authorgVisor bot <gvisor-bot@google.com>2020-04-21 19:20:51 +0000
committergVisor bot <gvisor-bot@google.com>2020-04-21 19:20:51 +0000
commitb5cdbb659d6ecd5a38090093369c81db76e8a152 (patch)
tree533d1ae7bafb1e27b601b62cc24b2cfc99ee6a5a /pkg/sentry/fsimpl/tmpfs/directory.go
parent3477221b21c89c56d64b039324513cda51b3f50a (diff)
parent9b5e305e05ef3ad51778981062d6152cea1cd4fb (diff)
Merge release-20200323.0-203-g9b5e305 (automated)
Diffstat (limited to 'pkg/sentry/fsimpl/tmpfs/directory.go')
-rwxr-xr-xpkg/sentry/fsimpl/tmpfs/directory.go84
1 files changed, 63 insertions, 21 deletions
diff --git a/pkg/sentry/fsimpl/tmpfs/directory.go b/pkg/sentry/fsimpl/tmpfs/directory.go
index 45712c9b9..f2399981b 100755
--- a/pkg/sentry/fsimpl/tmpfs/directory.go
+++ b/pkg/sentry/fsimpl/tmpfs/directory.go
@@ -15,35 +15,77 @@
package tmpfs
import (
+ "sync/atomic"
+
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
+ "gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/syserror"
)
type directory struct {
- inode inode
+ // Since directories can't be hard-linked, each directory can only be
+ // associated with a single dentry, which we can store in the directory
+ // struct.
+ dentry dentry
+ inode inode
+
+ // childMap maps the names of the directory's children to their dentries.
+ // childMap is protected by filesystem.mu.
+ childMap map[string]*dentry
- // childList is a list containing (1) child Dentries and (2) fake Dentries
+ // numChildren is len(childMap), but accessed using atomic memory
+ // operations to avoid locking in inode.statTo().
+ numChildren int64
+
+ // childList is a list containing (1) child dentries and (2) fake dentries
// (with inode == nil) that represent the iteration position of
// directoryFDs. childList is used to support directoryFD.IterDirents()
- // efficiently. childList is protected by filesystem.mu.
+ // efficiently. childList is protected by iterMu.
+ iterMu sync.Mutex
childList dentryList
}
-func (fs *filesystem) newDirectory(creds *auth.Credentials, mode linux.FileMode) *inode {
+func (fs *filesystem) newDirectory(creds *auth.Credentials, mode linux.FileMode) *directory {
dir := &directory{}
dir.inode.init(dir, fs, creds, linux.S_IFDIR|mode)
dir.inode.nlink = 2 // from "." and parent directory or ".." for root
- return &dir.inode
+ dir.dentry.inode = &dir.inode
+ dir.dentry.vfsd.Init(&dir.dentry)
+ return dir
+}
+
+// Preconditions: filesystem.mu must be locked for writing. dir must not
+// already contain a child with the given name.
+func (dir *directory) insertChildLocked(child *dentry, name string) {
+ child.parent = &dir.dentry
+ child.name = name
+ if dir.childMap == nil {
+ dir.childMap = make(map[string]*dentry)
+ }
+ dir.childMap[name] = child
+ atomic.AddInt64(&dir.numChildren, 1)
+ dir.iterMu.Lock()
+ dir.childList.PushBack(child)
+ dir.iterMu.Unlock()
+}
+
+// Preconditions: filesystem.mu must be locked for writing.
+func (dir *directory) removeChildLocked(child *dentry) {
+ delete(dir.childMap, child.name)
+ atomic.AddInt64(&dir.numChildren, -1)
+ dir.iterMu.Lock()
+ dir.childList.Remove(child)
+ dir.iterMu.Unlock()
}
type directoryFD struct {
fileDescription
vfs.DirectoryFileDescriptionDefaultImpl
- // Protected by filesystem.mu.
+ // Protected by directory.iterMu.
iter *dentry
off int64
}
@@ -51,11 +93,10 @@ type directoryFD struct {
// Release implements vfs.FileDescriptionImpl.Release.
func (fd *directoryFD) Release() {
if fd.iter != nil {
- fs := fd.filesystem()
dir := fd.inode().impl.(*directory)
- fs.mu.Lock()
+ dir.iterMu.Lock()
dir.childList.Remove(fd.iter)
- fs.mu.Unlock()
+ dir.iterMu.Unlock()
fd.iter = nil
}
}
@@ -63,10 +104,13 @@ func (fd *directoryFD) Release() {
// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallback) error {
fs := fd.filesystem()
- vfsd := fd.vfsfd.VirtualDentry().Dentry()
+ dir := fd.inode().impl.(*directory)
- fs.mu.Lock()
- defer fs.mu.Unlock()
+ // fs.mu is required to read d.parent and dentry.name.
+ fs.mu.RLock()
+ defer fs.mu.RUnlock()
+ dir.iterMu.Lock()
+ defer dir.iterMu.Unlock()
fd.inode().touchAtime(fd.vfsfd.Mount())
@@ -74,15 +118,16 @@ func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallba
if err := cb.Handle(vfs.Dirent{
Name: ".",
Type: linux.DT_DIR,
- Ino: vfsd.Impl().(*dentry).inode.ino,
+ Ino: dir.inode.ino,
NextOff: 1,
}); err != nil {
return err
}
fd.off++
}
+
if fd.off == 1 {
- parentInode := vfsd.ParentOrSelf().Impl().(*dentry).inode
+ parentInode := genericParentOrSelf(&dir.dentry).inode
if err := cb.Handle(vfs.Dirent{
Name: "..",
Type: parentInode.direntType(),
@@ -94,7 +139,6 @@ func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallba
fd.off++
}
- dir := vfsd.Impl().(*dentry).inode.impl.(*directory)
var child *dentry
if fd.iter == nil {
// Start iteration at the beginning of dir.
@@ -109,7 +153,7 @@ func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallba
// Skip other directoryFD iterators.
if child.inode != nil {
if err := cb.Handle(vfs.Dirent{
- Name: child.vfsd.Name(),
+ Name: child.name,
Type: child.inode.direntType(),
Ino: child.inode.ino,
NextOff: fd.off + 1,
@@ -127,9 +171,9 @@ func (fd *directoryFD) IterDirents(ctx context.Context, cb vfs.IterDirentsCallba
// Seek implements vfs.FileDescriptionImpl.Seek.
func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
- fs := fd.filesystem()
- fs.mu.Lock()
- defer fs.mu.Unlock()
+ dir := fd.inode().impl.(*directory)
+ dir.iterMu.Lock()
+ defer dir.iterMu.Unlock()
switch whence {
case linux.SEEK_SET:
@@ -157,8 +201,6 @@ func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (in
remChildren = offset - 2
}
- dir := fd.inode().impl.(*directory)
-
// Ensure that fd.iter exists and is not linked into dir.childList.
if fd.iter == nil {
fd.iter = &dentry{}