perkeep/pkg/fs/fs.go

// +build linux darwin

/*
Copyright 2011 Google Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// Package fs implements a FUSE filesystem for Camlistore and is
// used by the cammount binary.
package fs

import (
	"fmt"
	"io"
	"log"
	"os"
	"sync"
	"syscall"
	"time"

	"camlistore.org/pkg/blob"
	"camlistore.org/pkg/client"
	"camlistore.org/pkg/lru"
	"camlistore.org/pkg/schema"

	"camlistore.org/third_party/code.google.com/p/rsc/fuse"
)

var serverStart = time.Now()

var errNotDir = fuse.Errno(syscall.ENOTDIR)

type CamliFileSystem struct {
	fetcher blob.SeekFetcher
	client  *client.Client // or nil, if not doing search queries
	root    fuse.Node

	// IgnoreOwners, if true, collapses all file ownership to the
	// uid/gid running the fuse filesystem, and sets all the
	// permissions to 0600/0700.
	IgnoreOwners bool

	blobToSchema *lru.Cache // ~map[blobstring]*schema.Blob
	nameToBlob   *lru.Cache // ~map[string]blob.Ref
	nameToAttr   *lru.Cache // ~map[string]*fuse.Attr
}

var _ fuse.FS = (*CamliFileSystem)(nil)

func newCamliFileSystem(fetcher blob.SeekFetcher) *CamliFileSystem {
	return &CamliFileSystem{
		fetcher:      fetcher,
		blobToSchema: lru.New(1024), // arbitrary; TODO: tunable/smarter?
		nameToBlob:   lru.New(1024), // arbitrary: TODO: tunable/smarter?
		nameToAttr:   lru.New(1024), // arbitrary: TODO: tunable/smarter?
	}
}

// NewCamliFileSystem returns a filesystem with a generic base, from which users
// can navigate by blobref, tag, date, etc.
func NewCamliFileSystem(client *client.Client, fetcher blob.SeekFetcher) *CamliFileSystem {
	if client == nil || fetcher == nil {
		panic("nil argument")
	}
	fs := newCamliFileSystem(fetcher)
	fs.root = &root{fs: fs} // root.go
	fs.client = client
	return fs
}

// NewRootedCamliFileSystem returns a CamliFileSystem with root as its
// base.
func NewRootedCamliFileSystem(fetcher blob.SeekFetcher, root blob.Ref) (*CamliFileSystem, error) {
	fs := newCamliFileSystem(fetcher)

	blob, err := fs.fetchSchemaMeta(root)
	if err != nil {
		return nil, err
	}
	if blob.Type() != "directory" {
		return nil, fmt.Errorf("Blobref must be of a directory, got a %v", blob.Type())
	}
	n := &node{fs: fs, blobref: root, meta: blob}
	n.populateAttr()
	fs.root = n
	return fs, nil
}

// node implements fuse.Node with a read-only Camli "file" or
// "directory" blob.
type node struct {
	noXattr
	fs      *CamliFileSystem
	blobref blob.Ref

	pnodeModTime time.Time // optionally set by recent.go; modtime of permanode

	dmu     sync.Mutex    // guards dirents. acquire before mu.
	dirents []fuse.Dirent // nil until populated once

	mu      sync.Mutex // guards rest
	attr    fuse.Attr
	meta    *schema.Blob
	lookMap map[string]blob.Ref
}

func (n *node) Attr() (attr fuse.Attr) {
	_, err := n.schema()
	if err != nil {
		// Hm, can't return it. Just log it I guess.
		log.Printf("error fetching schema superset for %v: %v", n.blobref, err)
	}
	return n.attr
}

func (n *node) addLookupEntry(name string, ref blob.Ref) {
	n.mu.Lock()
	defer n.mu.Unlock()
	if n.lookMap == nil {
		n.lookMap = make(map[string]blob.Ref)
	}
	n.lookMap[name] = ref
}

func (n *node) Lookup(name string, intr fuse.Intr) (fuse.Node, fuse.Error) {
	if name == ".quitquitquit" {
		// TODO: only in dev mode
		log.Fatalf("Shutting down due to .quitquitquit lookup.")
	}

	// If we haven't done Readdir yet (dirents isn't set), then force a Readdir
	// call to populate lookMap.
	n.dmu.Lock()
	loaded := n.dirents != nil
	n.dmu.Unlock()
	if !loaded {
		n.ReadDir(nil)
	}

	n.mu.Lock()
	defer n.mu.Unlock()
	ref, ok := n.lookMap[name]
	if !ok {
		return nil, fuse.ENOENT
	}
	return &node{fs: n.fs, blobref: ref}, nil
}

func (n *node) schema() (*schema.Blob, error) {
	// TODO: use singleflight library here instead of a lock?
	n.mu.Lock()
	defer n.mu.Unlock()
	if n.meta != nil {
		return n.meta, nil
	}
	blob, err := n.fs.fetchSchemaMeta(n.blobref)
	if err == nil {
		n.meta = blob
		n.populateAttr()
	}
	return blob, err
}

func isWriteFlags(flags uint32) bool {
	return flags & uint32(os.O_WRONLY|os.O_RDWR|os.O_APPEND|os.O_CREATE) != 0
}

func (n *node) Open(req *fuse.OpenRequest, res *fuse.OpenResponse, intr fuse.Intr) (fuse.Handle, fuse.Error) {
	log.Printf("CAMLI Open on %v: %#v", n.blobref, req)
	if isWriteFlags(req.Flags) {
		return nil, fuse.EPERM
	}
	ss, err := n.schema()
	if err != nil {
		log.Printf("open of %v: %v", n.blobref, err)
		return nil, fuse.EIO
	}
	if ss.Type() == "directory" {
		return n, nil
	}
	fr, err := ss.NewFileReader(n.fs.fetcher)
	if err != nil {
		// Will only happen if ss.Type != "file" or "bytes"
		log.Printf("NewFileReader(%s) = %v", n.blobref, err)
		return nil, fuse.EIO
	}
	return &nodeReader{n: n, fr: fr}, nil
}

type nodeReader struct {
	n  *node
	fr *schema.FileReader
}

func (nr *nodeReader) Read(req *fuse.ReadRequest, res *fuse.ReadResponse, intr fuse.Intr) fuse.Error {
	log.Printf("CAMLI nodeReader READ on %v: %#v", nr.n.blobref, req)
	if req.Offset >= nr.fr.Size() {
		return nil
	}
	size := req.Size
	if int64(size)+req.Offset >= nr.fr.Size() {
		size -= int((int64(size) + req.Offset) - nr.fr.Size())
	}
	buf := make([]byte, size)
	n, err := nr.fr.ReadAt(buf, req.Offset)
	if err == io.EOF {
		err = nil
	}
	if err != nil {
		log.Printf("camli read on %v at %d: %v", nr.n.blobref, req.Offset, err)
		return fuse.EIO
	}
	res.Data = buf[:n]
	return nil
}

func (nr *nodeReader) Release(req *fuse.ReleaseRequest, intr fuse.Intr) fuse.Error {
	log.Printf("CAMLI nodeReader RELEASE on %v", nr.n.blobref)
	nr.fr.Close()
	return nil
}

func (n *node) ReadDir(intr fuse.Intr) ([]fuse.Dirent, fuse.Error) {
	log.Printf("CAMLI ReadDir on %v", n.blobref)
	n.dmu.Lock()
	defer n.dmu.Unlock()
	if n.dirents != nil {
		return n.dirents, nil
	}

	ss, err := n.schema()
	if err != nil {
		log.Printf("camli.ReadDir error on %v: %v", n.blobref, err)
		return nil, fuse.EIO
	}
	dr, err := schema.NewDirReader(n.fs.fetcher, ss.BlobRef())
	if err != nil {
		log.Printf("camli.ReadDir error on %v: %v", n.blobref, err)
		return nil, fuse.EIO
	}
	schemaEnts, err := dr.Readdir(-1)
	if err != nil {
		log.Printf("camli.ReadDir error on %v: %v", n.blobref, err)
		return nil, fuse.EIO
	}
	n.dirents = make([]fuse.Dirent, 0)
	for _, sent := range schemaEnts {
		if name := sent.FileName(); name != "" {
			n.addLookupEntry(name, sent.BlobRef())
			n.dirents = append(n.dirents, fuse.Dirent{Name: name})
		}
	}
	return n.dirents, nil
}

// populateAttr should only be called once n.ss is known to be set and
// non-nil
func (n *node) populateAttr() error {
	meta := n.meta

	n.attr.Mode = meta.FileMode()

	if n.fs.IgnoreOwners {
		n.attr.Uid = uint32(os.Getuid())
		n.attr.Gid = uint32(os.Getgid())
		executeBit := n.attr.Mode & 0100
		n.attr.Mode = (n.attr.Mode ^ n.attr.Mode.Perm()) & 0400 & executeBit
	} else {
		n.attr.Uid = uint32(meta.MapUid())
		n.attr.Gid = uint32(meta.MapGid())
	}

	// TODO: inode?

	if mt := meta.ModTime(); !mt.IsZero() {
		n.attr.Mtime = mt
	} else {
		n.attr.Mtime = n.pnodeModTime
	}

	switch meta.Type() {
	case "file":
		n.attr.Size = uint64(meta.PartsSize())
		n.attr.Blocks = 0 // TODO: set?
		n.attr.Mode |= 0400
	case "directory":
		n.attr.Mode |= 0500
	case "symlink":
		n.attr.Mode |= 0400
	default:
		log.Printf("unknown attr ss.Type %q in populateAttr", meta.Type())
	}
	return nil
}

func (fs *CamliFileSystem) Root() (fuse.Node, fuse.Error) {
	return fs.root, nil
}

func (fs *CamliFileSystem) Statfs(req *fuse.StatfsRequest, res *fuse.StatfsResponse, intr fuse.Intr) fuse.Error {
	// Make some stuff up, just to see if it makes "lsof" happy.
	res.Blocks = 1 << 35
	res.Bfree = 1 << 34
	res.Bavail = 1 << 34
	res.Files = 1 << 29
	res.Ffree = 1 << 28
	res.Namelen = 2048
	res.Bsize = 1024
	return nil
}

// Errors returned are:
//    os.ErrNotExist -- blob not found
//    os.ErrInvalid -- not JSON or a camli schema blob
func (fs *CamliFileSystem) fetchSchemaMeta(br blob.Ref) (*schema.Blob, error) {
	blobStr := br.String()
	if blob, ok := fs.blobToSchema.Get(blobStr); ok {
		return blob.(*schema.Blob), nil
	}

	rsc, _, err := fs.fetcher.Fetch(br)
	if err != nil {
		return nil, err
	}
	defer rsc.Close()
	blob, err := schema.BlobFromReader(br, rsc)
	if err != nil {
		log.Printf("Error parsing %s as schema blob: %v", br, err)
		return nil, os.ErrInvalid
	}
	if blob.Type() == "" {
		log.Printf("blob %s is JSON but lacks camliType", br)
		return nil, os.ErrInvalid
	}
	fs.blobToSchema.Add(blobStr, blob)
	return blob, nil
}

type notImplementDirNode struct{ noXattr }

func (notImplementDirNode) Attr() fuse.Attr {
	return fuse.Attr{
		Mode: os.ModeDir | 0000,
		Uid:  uint32(os.Getuid()),
		Gid:  uint32(os.Getgid()),
	}
}

type staticFileNode string

func (s staticFileNode) Attr() fuse.Attr {
	return fuse.Attr{
		Mode:   0400,
		Uid:    uint32(os.Getuid()),
		Gid:    uint32(os.Getgid()),
		Size:   uint64(len(s)),
		Mtime:  serverStart,
		Ctime:  serverStart,
		Crtime: serverStart,
	}
}

func (s staticFileNode) Read(req *fuse.ReadRequest, res *fuse.ReadResponse, intr fuse.Intr) fuse.Error {
	if req.Offset > int64(len(s)) {
		return nil
	}
	s = s[req.Offset:]
	size := req.Size
	if size > len(s) {
		size = len(s)
	}
	res.Data = make([]byte, size)
	copy(res.Data, s)
	return nil
}

func (n staticFileNode) Getxattr(*fuse.GetxattrRequest, *fuse.GetxattrResponse, fuse.Intr) fuse.Error {
	return fuse.ENOATTR
}

func (n staticFileNode) Listxattr(*fuse.ListxattrRequest, *fuse.ListxattrResponse, fuse.Intr) fuse.Error {
	return nil
}

func (n staticFileNode) Setxattr(*fuse.SetxattrRequest, fuse.Intr) fuse.Error {
	return fuse.EPERM
}

func (n staticFileNode) Removexattr(*fuse.RemovexattrRequest, fuse.Intr) fuse.Error {
	return fuse.EPERM
}