130 lines
3.2 KiB
Go
130 lines
3.2 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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// Author: jacobsa@google.com (Aaron Jacobs)
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package memfs
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import (
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"fmt"
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"github.com/jacobsa/fuse"
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"github.com/jacobsa/fuse/fuseutil"
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"github.com/jacobsa/gcloud/syncutil"
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"github.com/jacobsa/gcsfuse/timeutil"
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"golang.org/x/net/context"
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)
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type memFS struct {
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fuseutil.NotImplementedFileSystem
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/////////////////////////
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// Dependencies
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/////////////////////////
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clock timeutil.Clock
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/////////////////////////
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// Mutable state
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/////////////////////////
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mu syncutil.InvariantMutex
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// The collection of all inodes that have ever been created, indexed by inode
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// ID. Some inodes are not in use if they have been unlinked, and no inode
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// with ID less than fuse.RootInodeID is ever used.
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//
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// INVARIANT: len(inodes) > fuse.RootInodeID
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// INVARIANT: For all i < fuse.RootInodeID, inodes[i].impl == nil
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// INVARIANT: inodes[fuse.RootInodeID].impl is of type *memDir
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inodes []inode // GUARDED_BY(mu)
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// A list of inode IDs within inodes available for reuse, not including the
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// reserved IDs less than fuse.RootInodeID.
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//
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// INVARIANT: This is all and only indices i of inodes such that i >
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// fuse.RootInodeID and inodes[i].impl == nil
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freeInodes []fuse.InodeID // GUARDED_BY(mu)
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}
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// Create a file system that stores data and metadata in memory.
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func NewMemFS(
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clock timeutil.Clock) (fs fuse.FileSystem) {
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fs = &memFS{
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clock: clock,
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}
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fs.(*memFS).mu = syncutil.NewInvariantMutex(fs.(*memFS).checkInvariants)
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return
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}
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func (fs *memFS) checkInvariants() {
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// Check general inode invariants.
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for i := range fs.inodes {
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fs.inodes[i].checkInvariants()
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}
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// Check reserved inodes.
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for i := 0; i < fuse.RootInodeID; i++ {
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var inode *inode = &fs.inodes[i]
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if inode.impl != nil {
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panic(fmt.Sprintf("Non-nil impl for ID: %v", i))
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}
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}
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// Check the root inode.
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_ = fs.inodes[fuse.RootInodeID].impl.(*memDir)
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// Check inodes, building our own set of free IDs.
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freeIDsEncountered := make(map[fuse.InodeID]struct{})
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for i := fuse.RootInodeID + 1; i < len(fs.inodes); i++ {
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var inode *inode = &fs.inodes[i]
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if inode.impl == nil {
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freeIDsEncountered[fuse.InodeID(i)] = struct{}{}
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continue
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}
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}
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// Check fs.freeInodes.
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if len(fs.freeInodes) != len(freeIDsEncountered) {
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panic(
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fmt.Sprintf(
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"Length mismatch: %v vs. %v",
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len(fs.freeInodes),
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len(freeIDsEncountered)))
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}
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for _, id := range fs.freeInodes {
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if _, ok := freeIDsEncountered[id]; !ok {
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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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}
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func (fs *memFS) Init(
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ctx context.Context,
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req *fuse.InitRequest) (resp *fuse.InitResponse, err error) {
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resp = &fuse.InitResponse{}
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return
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}
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func (fs *memFS) OpenDir(
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ctx context.Context,
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req *fuse.OpenDirRequest) (resp *fuse.OpenDirResponse, err error) {
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// We don't mutate spontaneosuly, so if the VFS layer has asked for an
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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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if req.Inode >= fuse.InodeID(len(fs.inodes)) {
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panic(fmt.Sprintf("Inode out of range: %v vs. %v", req.Inode, len(fs.inodes)))
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}
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var inode *inode = &fs.inodes[req.Inode]
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if inode.impl == nil {
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panic(fmt.Sprintf("Dead inode requested: %v", req.Inode))
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}
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// All is good.
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return
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}
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