516 lines
12 KiB
Go
516 lines
12 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package memfs
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import (
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"fmt"
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"io"
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"os"
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"time"
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"github.com/googlecloudplatform/gcsfuse/timeutil"
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"github.com/jacobsa/fuse"
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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/gcloud/syncutil"
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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 fuseops.RootInodeID is ever
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// used.
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//
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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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// INVARIANT: inodes[fuseops.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 fuseops.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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// fuseops.RootInodeID and inodes[i] == nil
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freeInodes []fuseops.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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//
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// The supplied UID/GID pair will own the root inode. This file system does no
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// permissions checking, and should therefore be mounted with the
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// default_permissions option.
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func NewMemFS(
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uid uint32,
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gid uint32,
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clock timeutil.Clock) fuse.Server {
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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, fuseops.RootInodeID+1),
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}
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// Set up the root inode.
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rootAttrs := fuseops.InodeAttributes{
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Mode: 0700 | os.ModeDir,
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Uid: uid,
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Gid: gid,
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}
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fs.inodes[fuseops.RootInodeID] = newInode(clock, rootAttrs)
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// Set up invariant checking.
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fs.mu = syncutil.NewInvariantMutex(fs.checkInvariants)
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return fuseutil.NewFileSystemServer(fs)
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}
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////////////////////////////////////////////////////////////////////////
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// Helpers
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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 < fuseops.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[fuseops.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[fuseops.InodeID]struct{})
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for i := fuseops.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[fuseops.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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// 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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//
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// SHARED_LOCKS_REQUIRED(fs.mu)
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// EXCLUSIVE_LOCK_FUNCTION(inode.mu)
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func (fs *memFS) getInodeForModifyingOrDie(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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// Find the given inode and return it with its lock held for reading. Panic if
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// 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 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.RLock()
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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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//
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// EXCLUSIVE_LOCKS_REQUIRED(fs.mu)
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// EXCLUSIVE_LOCK_FUNCTION(inode.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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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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if numFree != 0 {
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id = fs.freeInodes[numFree-1]
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fs.freeInodes = fs.freeInodes[:numFree-1]
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fs.inodes[id] = inode
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} else {
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id = fuseops.InodeID(len(fs.inodes))
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fs.inodes = append(fs.inodes, inode)
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}
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return
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}
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// EXCLUSIVE_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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}
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////////////////////////////////////////////////////////////////////////
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// FileSystem methods
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////////////////////////////////////////////////////////////////////////
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func (fs *memFS) Init(
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op *fuseops.InitOp) (err error) {
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return
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}
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func (fs *memFS) LookUpInode(
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op *fuseops.LookUpInodeOp) (err error) {
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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(op.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(op.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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op.Entry.Child = childID
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op.Entry.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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op.Entry.AttributesExpiration = fs.clock.Now().Add(365 * 24 * time.Hour)
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op.Entry.EntryExpiration = op.Entry.EntryExpiration
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return
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}
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func (fs *memFS) GetInodeAttributes(
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op *fuseops.GetInodeAttributesOp) (err error) {
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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(op.Inode)
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defer inode.mu.RUnlock()
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// Fill in the response.
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op.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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op.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) SetInodeAttributes(
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op *fuseops.SetInodeAttributesOp) (err error) {
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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.getInodeForModifyingOrDie(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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// Fill in the response.
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op.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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op.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) MkDir(
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op *fuseops.MkDirOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeForModifyingOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Set up attributes from the child, using the credentials of the calling
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// process as owner (matching inode_init_owner, cf. http://goo.gl/5qavg8).
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childAttrs := fuseops.InodeAttributes{
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Nlink: 1,
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Mode: op.Mode,
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Uid: op.Header().Uid,
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Gid: op.Header().Gid,
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}
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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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// Fill in the response.
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op.Entry.Child = childID
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op.Entry.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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op.Entry.AttributesExpiration = fs.clock.Now().Add(365 * 24 * time.Hour)
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op.Entry.EntryExpiration = op.Entry.EntryExpiration
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return
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}
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func (fs *memFS) CreateFile(
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op *fuseops.CreateFileOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeForModifyingOrDie(op.Parent)
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defer parent.mu.Unlock()
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// Set up attributes from the child, using the credentials of the calling
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// process as owner (matching inode_init_owner, cf. http://goo.gl/5qavg8).
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now := fs.clock.Now()
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childAttrs := fuseops.InodeAttributes{
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Nlink: 1,
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Mode: op.Mode,
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Atime: now,
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Mtime: now,
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Ctime: now,
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Crtime: now,
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Uid: op.Header().Uid,
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Gid: op.Header().Gid,
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}
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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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// Fill in the response entry.
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op.Entry.Child = childID
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op.Entry.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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op.Entry.AttributesExpiration = fs.clock.Now().Add(365 * 24 * time.Hour)
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op.Entry.EntryExpiration = op.Entry.EntryExpiration
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// We have nothing interesting to put in the Handle field.
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return
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}
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func (fs *memFS) RmDir(
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op *fuseops.RmDirOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeForModifyingOrDie(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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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.getInodeForModifyingOrDie(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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err = fuse.ENOTEMPTY
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return
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}
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// Remove the entry within the parent.
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parent.RemoveChild(op.Name)
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// Mark the child as unlinked.
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child.attributes.Nlink--
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return
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}
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func (fs *memFS) Unlink(
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op *fuseops.UnlinkOp) (err error) {
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fs.mu.Lock()
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defer fs.mu.Unlock()
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// Grab the parent, which we will update shortly.
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parent := fs.getInodeForModifyingOrDie(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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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.getInodeForModifyingOrDie(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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// Mark the child as unlinked.
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child.attributes.Nlink--
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return
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}
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func (fs *memFS) OpenDir(
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op *fuseops.OpenDirOp) (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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inode := fs.getInodeForReadingOrDie(op.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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op *fuseops.ReadDirOp) (err error) {
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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(op.Inode)
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defer inode.mu.RUnlock()
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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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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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func (fs *memFS) OpenFile(
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op *fuseops.OpenFileOp) (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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inode := fs.getInodeForReadingOrDie(op.Inode)
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defer inode.mu.RUnlock()
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if inode.dir {
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panic("Found directory.")
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}
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return
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}
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func (fs *memFS) ReadFile(
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op *fuseops.ReadFileOp) (err error) {
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// Find the inode in question.
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inode := fs.getInodeForReadingOrDie(op.Inode)
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defer inode.mu.RUnlock()
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// Serve the request.
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op.Data = make([]byte, op.Size)
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n, err := inode.ReadAt(op.Data, op.Offset)
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op.Data = op.Data[:n]
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// Don't return EOF errors; we just indicate EOF to fuse using a short read.
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if err == io.EOF {
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err = nil
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}
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return
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}
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func (fs *memFS) WriteFile(
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op *fuseops.WriteFileOp) (err error) {
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fs.mu.RLock()
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defer fs.mu.RUnlock()
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// Find the inode in question.
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inode := fs.getInodeForModifyingOrDie(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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return
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}
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