231 lines
5.5 KiB
Go
231 lines
5.5 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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"time"
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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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// 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 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] == nil
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// INVARIANT: inodes[fuse.RootInodeID] != nil
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// INVARIANT: inodes[fuse.RootInodeID].dir is true
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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] == 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) fuse.FileSystem {
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// Set up the basic struct.
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fs := &memFS{
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clock: clock,
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inodes: make([]*inode, fuse.RootInodeID+1),
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}
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// Set up the root inode.
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fs.inodes[fuse.RootInodeID] = newInode(true) // dir
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// Set up invariant checking.
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fs.mu = syncutil.NewInvariantMutex(fs.checkInvariants)
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return fs
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}
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func (fs *memFS) checkInvariants() {
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// Check reserved inodes.
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for i := 0; i < fuse.RootInodeID; i++ {
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if fs.inodes[i] != nil {
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panic(fmt.Sprintf("Non-nil inode for ID: %v", i))
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}
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}
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// Check the root inode.
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if !fs.inodes[fuse.RootInodeID].dir {
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panic("Expected root to be a directory.")
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}
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// Build our own list 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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inode := fs.inodes[i]
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if inode == 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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// Find the supplied inode and return it with its lock held for reading. Panic
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// if it doesn't exist.
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//
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// SHARED_LOCKS_REQUIRED(fs.mu)
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// SHARED_LOCK_FUNCTION(inode.mu)
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func (fs *memFS) getInodeForReadingOrDie(id fuse.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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return
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}
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func (fs *memFS) LookUpInode(
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ctx context.Context,
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req *fuse.LookUpInodeRequest) (resp *fuse.LookUpInodeResponse, err error) {
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resp = &fuse.LookUpInodeResponse{}
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// Grab the parent directory.
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inode := fs.getInodeForReadingOrDie(req.Parent)
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defer inode.mu.RUnlock()
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// Does the directory have an entry with the given name?
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childID, ok := inode.LookUpChild(req.Name)
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if !ok {
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err = fuse.ENOENT
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return
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}
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// Grab the child.
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child := fs.getInodeForReadingOrDie(childID)
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defer child.mu.RUnlock()
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// Fill in the response.
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resp.Attributes = child.attributes
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// We don't spontaneously mutate, so the kernel can cache as long as it wants
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// (since it also handles invalidation).
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resp.AttributesExpiration = fs.clock.Now().Add(365 * 24 * time.Hour)
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resp.EntryExpiration = resp.EntryExpiration
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return
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}
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func (fs *memFS) GetInodeAttributes(
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ctx context.Context,
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req *fuse.GetInodeAttributesRequest) (
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resp *fuse.GetInodeAttributesResponse, err error) {
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resp = &fuse.GetInodeAttributesResponse{}
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// Grab the inode.
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inode := fs.getInodeForReadingOrDie(req.Inode)
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defer inode.mu.RUnlock()
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// Fill in the response.
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resp.Attributes = inode.attributes
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// We don't spontaneously mutate, so the kernel can cache as long as it wants
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// (since it also handles invalidation).
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resp.AttributesExpiration = fs.clock.Now().Add(365 * 24 * time.Hour)
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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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resp = &fuse.OpenDirResponse{}
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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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inode := fs.getInodeForReadingOrDie(req.Inode)
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defer inode.mu.RUnlock()
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if !inode.dir {
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panic("Found non-dir.")
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}
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return
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}
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func (fs *memFS) ReadDir(
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ctx context.Context,
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req *fuse.ReadDirRequest) (resp *fuse.ReadDirResponse, err error) {
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resp = &fuse.ReadDirResponse{}
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// Grab the directory.
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inode := fs.getInodeForReadingOrDie(req.Inode)
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defer inode.mu.RUnlock()
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if !inode.dir {
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panic("Found non-dir.")
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}
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// Serve the request.
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resp.Data, err = inode.ReadDir(int(req.Offset), req.Size)
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if err != nil {
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err = fmt.Errorf("inode.ReadDir: %v", err)
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return
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}
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return
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}
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