Simplified memfs locking.
Aaron Jacobs
commit
10b71ca55f
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@ -22,11 +22,12 @@ import (
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"github.com/jacobsa/fuse/fuseops"
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"github.com/jacobsa/fuse/fuseutil"
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"github.com/jacobsa/syncutil"
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"github.com/jacobsa/timeutil"
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)
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// Common attributes for files and directories.
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//
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// External synchronization is required.
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type inode struct {
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/////////////////////////
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// Dependencies
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@ -38,8 +39,6 @@ type inode struct {
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// Mutable state
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/////////////////////////
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mu syncutil.InvariantMutex
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// The current attributes of this inode.
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//
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// INVARIANT: attrs.Mode &^ (os.ModePerm|os.ModeDir|os.ModeSymlink) == 0
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@ -93,11 +92,10 @@ func newInode(
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attrs: attrs,
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}
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in.mu = syncutil.NewInvariantMutex(in.checkInvariants)
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return
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}
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func (in *inode) checkInvariants() {
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func (in *inode) CheckInvariants() {
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// INVARIANT: attrs.Mode &^ (os.ModePerm|os.ModeDir|os.ModeSymlink) == 0
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if !(in.attrs.Mode&^(os.ModePerm|os.ModeDir|os.ModeSymlink) == 0) {
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panic(fmt.Sprintf("Unexpected mode: %v", in.attrs.Mode))
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@ -153,25 +151,21 @@ func (in *inode) checkInvariants() {
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return
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}
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) isDir() bool {
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return in.attrs.Mode&os.ModeDir != 0
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}
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) isSymlink() bool {
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return in.attrs.Mode&os.ModeSymlink != 0
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}
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) isFile() bool {
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return !(in.isDir() || in.isSymlink())
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}
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// Return the index of the child within in.entries, if it exists.
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//
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// REQUIRES: in.dir
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// LOCKS_REQUIRED(in.mu)
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// REQUIRES: in.isDir()
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func (in *inode) findChild(name string) (i int, ok bool) {
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if !in.isDir() {
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panic("findChild called on non-directory.")
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@ -195,7 +189,6 @@ func (in *inode) findChild(name string) (i int, ok bool) {
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// Return the number of children of the directory.
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//
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// REQUIRES: in.isDir()
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) Len() (n int) {
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for _, e := range in.entries {
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if e.Type != fuseutil.DT_Unknown {
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@ -209,7 +202,6 @@ func (in *inode) Len() (n int) {
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// Find an entry for the given child name and return its inode ID.
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//
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// REQUIRES: in.isDir()
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) LookUpChild(name string) (id fuseops.InodeID, ok bool) {
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index, ok := in.findChild(name)
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if ok {
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@ -223,7 +215,6 @@ func (in *inode) LookUpChild(name string) (id fuseops.InodeID, ok bool) {
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//
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// REQUIRES: in.isDir()
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// REQUIRES: dt != fuseutil.DT_Unknown
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) AddChild(
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id fuseops.InodeID,
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name string,
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@ -263,7 +254,6 @@ func (in *inode) AddChild(
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//
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// REQUIRES: in.isDir()
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// REQUIRES: An entry for the given name exists.
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) RemoveChild(name string) {
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// Update the modification time.
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in.attrs.Mtime = in.clock.Now()
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@ -284,7 +274,6 @@ func (in *inode) RemoveChild(name string) {
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// Serve a ReadDir request.
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//
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// REQUIRES: in.isDir()
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) ReadDir(offset int, size int) (data []byte, err error) {
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if !in.isDir() {
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panic("ReadDir called on non-directory.")
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@ -313,7 +302,6 @@ func (in *inode) ReadDir(offset int, size int) (data []byte, err error) {
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// Read from the file's contents. See documentation for ioutil.ReaderAt.
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//
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// REQUIRES: in.isFile()
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) ReadAt(p []byte, off int64) (n int, err error) {
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if !in.isFile() {
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panic("ReadAt called on non-file.")
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@ -337,7 +325,6 @@ func (in *inode) ReadAt(p []byte, off int64) (n int, err error) {
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// Write to the file's contents. See documentation for ioutil.WriterAt.
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//
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// REQUIRES: in.isFile()
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) WriteAt(p []byte, off int64) (n int, err error) {
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if !in.isFile() {
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panic("WriteAt called on non-file.")
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@ -366,8 +353,6 @@ func (in *inode) WriteAt(p []byte, off int64) (n int, err error) {
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}
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// Update attributes from non-nil parameters.
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//
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// LOCKS_REQUIRED(in.mu)
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func (in *inode) SetAttributes(
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size *uint64,
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mode *os.FileMode,
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@ -40,13 +40,13 @@ type memFS struct {
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// Mutable state
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/////////////////////////
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// When acquiring this lock, the caller must hold no inode locks.
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mu syncutil.InvariantMutex
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// The collection of live inodes, indexed by ID. IDs of free inodes that may
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// be re-used have nil entries. No ID less than fuseops.RootInodeID is ever
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// used.
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//
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// INVARIANT: For each inode in, in.CheckInvariants() does not panic.
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// INVARIANT: len(inodes) > fuseops.RootInodeID
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// INVARIANT: For all i < fuseops.RootInodeID, inodes[i] == nil
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// INVARIANT: inodes[fuseops.RootInodeID] != nil
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@ -132,33 +132,32 @@ func (fs *memFS) checkInvariants() {
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panic(fmt.Sprintf("Unexected free inode ID: %v", id))
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}
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}
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// INVARIANT: For each inode in, in.CheckInvariants() does not panic.
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for _, in := range fs.inodes {
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in.CheckInvariants()
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}
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}
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// Find the given inode and return it with its lock held. Panic if it doesn't
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// exist.
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// Find the given inode. Panic if it doesn't exist.
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//
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// LOCKS_REQUIRED(fs.mu)
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// LOCK_FUNCTION(inode.mu)
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func (fs *memFS) getInodeOrDie(id fuseops.InodeID) (inode *inode) {
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inode = fs.inodes[id]
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if inode == nil {
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panic(fmt.Sprintf("Unknown inode: %v", id))
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}
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inode.mu.Lock()
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return
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}
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// Allocate a new inode, assigning it an ID that is not in use. Return it with
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// its lock held.
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// Allocate a new inode, assigning it an ID that is not in use.
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//
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// EXCLUSIVE_LOCKS_REQUIRED(fs.mu)
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// EXCLUSIVE_LOCK_FUNCTION(inode.mu)
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// LOCKS_REQUIRED(fs.mu)
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func (fs *memFS) allocateInode(
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attrs fuseops.InodeAttributes) (id fuseops.InodeID, inode *inode) {
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// Create and lock the inode.
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// Create the inode.
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inode = newInode(fs.clock, attrs)
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inode.mu.Lock()
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// Re-use a free ID if possible. Otherwise mint a new one.
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numFree := len(fs.freeInodes)
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@ -174,7 +173,7 @@ func (fs *memFS) allocateInode(
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return
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}
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// EXCLUSIVE_LOCKS_REQUIRED(fs.mu)
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// LOCKS_REQUIRED(fs.mu)
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func (fs *memFS) deallocateInode(id fuseops.InodeID) {
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fs.freeInodes = append(fs.freeInodes, id)
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fs.inodes[id] = nil
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@ -191,7 +190,6 @@ func (fs *memFS) LookUpInode(
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// Grab the parent directory.
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inode := fs.getInodeOrDie(op.Parent)
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defer inode.mu.Unlock()
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// Does the directory have an entry with the given name?
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childID, ok := inode.LookUpChild(op.Name)
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@ -202,7 +200,6 @@ func (fs *memFS) LookUpInode(
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// Grab the child.
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child := fs.getInodeOrDie(childID)
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defer child.mu.Unlock()
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// Fill in the response.
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op.Entry.Child = childID
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@ -223,7 +220,6 @@ func (fs *memFS) GetInodeAttributes(
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// Grab the inode.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Fill in the response.
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op.Attributes = inode.attrs
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@ -242,7 +238,6 @@ func (fs *memFS) SetInodeAttributes(
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// Grab the inode.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Handle the request.
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inode.SetAttributes(op.Size, op.Mode, op.Mtime)
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@ -264,7 +259,6 @@ func (fs *memFS) MkDir(
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Ensure that the name doesn't already exist, so we don't wind up with a
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// duplicate.
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@ -285,7 +279,6 @@ func (fs *memFS) MkDir(
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// Allocate a child.
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childID, child := fs.allocateInode(childAttrs)
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defer child.mu.Unlock()
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// Add an entry in the parent.
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parent.AddChild(childID, op.Name, fuseutil.DT_Directory)
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@ -309,7 +302,6 @@ func (fs *memFS) CreateFile(
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Ensure that the name doesn't already exist, so we don't wind up with a
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// duplicate.
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@ -335,7 +327,6 @@ func (fs *memFS) CreateFile(
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// Allocate a child.
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childID, child := fs.allocateInode(childAttrs)
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defer child.mu.Unlock()
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// Add an entry in the parent.
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parent.AddChild(childID, op.Name, fuseutil.DT_File)
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@ -361,7 +352,6 @@ func (fs *memFS) CreateSymlink(
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Ensure that the name doesn't already exist, so we don't wind up with a
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// duplicate.
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@ -387,7 +377,6 @@ func (fs *memFS) CreateSymlink(
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// Allocate a child.
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childID, child := fs.allocateInode(childAttrs)
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defer child.mu.Unlock()
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// Set up its target.
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child.target = op.Target
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@ -414,7 +403,6 @@ func (fs *memFS) RmDir(
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Find the child within the parent.
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childID, ok := parent.LookUpChild(op.Name)
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@ -425,7 +413,6 @@ func (fs *memFS) RmDir(
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// Grab the child.
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child := fs.getInodeOrDie(childID)
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defer child.mu.Unlock()
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// Make sure the child is empty.
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if child.Len() != 0 {
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@ -449,7 +436,6 @@ func (fs *memFS) Unlink(
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Find the child within the parent.
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childID, ok := parent.LookUpChild(op.Name)
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@ -460,7 +446,6 @@ func (fs *memFS) Unlink(
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// Grab the child.
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child := fs.getInodeOrDie(childID)
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defer child.mu.Unlock()
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// Remove the entry within the parent.
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parent.RemoveChild(op.Name)
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@ -480,7 +465,6 @@ func (fs *memFS) OpenDir(
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// inode that doesn't exist, something screwed up earlier (a lookup, a
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// cache invalidation, etc.).
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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if !inode.isDir() {
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panic("Found non-dir.")
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@ -496,7 +480,6 @@ func (fs *memFS) ReadDir(
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// Grab the directory.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Serve the request.
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op.Data, err = inode.ReadDir(int(op.Offset), op.Size)
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@ -517,7 +500,6 @@ func (fs *memFS) OpenFile(
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// inode that doesn't exist, something screwed up earlier (a lookup, a
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// cache invalidation, etc.).
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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if !inode.isFile() {
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panic("Found non-file.")
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@ -533,7 +515,6 @@ func (fs *memFS) ReadFile(
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// Find the inode in question.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Serve the request.
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op.Data = make([]byte, op.Size)
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@ -555,7 +536,6 @@ func (fs *memFS) WriteFile(
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// Find the inode in question.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Serve the request.
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_, err = inode.WriteAt(op.Data, op.Offset)
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@ -570,7 +550,6 @@ func (fs *memFS) ReadSymlink(
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// Find the inode in question.
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inode := fs.getInodeOrDie(op.Inode)
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defer inode.mu.Unlock()
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// Serve the request.
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op.Target = inode.target
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