// Copyright 2019 The gVisor Authors. // // 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 gofer provides a filesystem implementation that is backed by a 9p // server, interchangably referred to as "gofers" throughout this package. // // Lock order: // regularFileFD/directoryFD.mu // filesystem.renameMu // dentry.dirMu // filesystem.syncMu // dentry.metadataMu // *** "memmap.Mappable locks" below this point // dentry.mapsMu // *** "memmap.Mappable locks taken by Translate" below this point // dentry.handleMu // dentry.dataMu // // Locking dentry.dirMu in multiple dentries requires holding // filesystem.renameMu for writing. package gofer import ( "fmt" "strconv" "strings" "sync" "sync/atomic" "syscall" "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" "gvisor.dev/gvisor/pkg/log" "gvisor.dev/gvisor/pkg/p9" "gvisor.dev/gvisor/pkg/sentry/fs/fsutil" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time" "gvisor.dev/gvisor/pkg/sentry/memmap" "gvisor.dev/gvisor/pkg/sentry/pgalloc" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/syserror" "gvisor.dev/gvisor/pkg/unet" "gvisor.dev/gvisor/pkg/usermem" ) // Name is the default filesystem name. const Name = "9p" // FilesystemType implements vfs.FilesystemType. type FilesystemType struct{} // filesystem implements vfs.FilesystemImpl. type filesystem struct { vfsfs vfs.Filesystem // mfp is used to allocate memory that caches regular file contents. mfp is // immutable. mfp pgalloc.MemoryFileProvider // Immutable options. opts filesystemOptions // client is the client used by this filesystem. client is immutable. client *p9.Client // clock is a realtime clock used to set timestamps in file operations. clock ktime.Clock // uid and gid are the effective KUID and KGID of the filesystem's creator, // and are used as the owner and group for files that don't specify one. // uid and gid are immutable. uid auth.KUID gid auth.KGID // renameMu serves two purposes: // // - It synchronizes path resolution with renaming initiated by this // client. // // - It is held by path resolution to ensure that reachable dentries remain // valid. A dentry is reachable by path resolution if it has a non-zero // reference count (such that it is usable as vfs.ResolvingPath.Start() or // is reachable from its children), or if it is a child dentry (such that // it is reachable from its parent). renameMu sync.RWMutex // cachedDentries contains all dentries with 0 references. (Due to race // conditions, it may also contain dentries with non-zero references.) // cachedDentriesLen is the number of dentries in cachedDentries. These // fields are protected by renameMu. cachedDentries dentryList cachedDentriesLen uint64 // dentries contains all dentries in this filesystem. specialFileFDs // contains all open specialFileFDs. These fields are protected by syncMu. syncMu sync.Mutex dentries map[*dentry]struct{} specialFileFDs map[*specialFileFD]struct{} } type filesystemOptions struct { // "Standard" 9P options. fd int aname string interop InteropMode // derived from the "cache" mount option msize uint32 version string // maxCachedDentries is the maximum number of dentries with 0 references // retained by the client. maxCachedDentries uint64 // If forcePageCache is true, host FDs may not be used for application // memory mappings even if available; instead, the client must perform its // own caching of regular file pages. This is primarily useful for testing. forcePageCache bool // If limitHostFDTranslation is true, apply maxFillRange() constraints to // host FD mappings returned by dentry.(memmap.Mappable).Translate(). This // makes memory accounting behavior more consistent between cases where // host FDs are / are not available, but may increase the frequency of // sentry-handled page faults on files for which a host FD is available. limitHostFDTranslation bool // If overlayfsStaleRead is true, O_RDONLY host FDs provided by the remote // filesystem may not be coherent with writable host FDs opened later, so // mappings of the former must be replaced by mappings of the latter. This // is usually only the case when the remote filesystem is an overlayfs // mount on Linux < 4.19. overlayfsStaleRead bool // If regularFilesUseSpecialFileFD is true, application FDs representing // regular files will use distinct file handles for each FD, in the same // way that application FDs representing "special files" such as sockets // do. Note that this disables client caching and mmap for regular files. regularFilesUseSpecialFileFD bool } // InteropMode controls the client's interaction with other remote filesystem // users. type InteropMode uint32 const ( // InteropModeExclusive is appropriate when the filesystem client is the // only user of the remote filesystem. // // - The client may cache arbitrary filesystem state (file data, metadata, // filesystem structure, etc.). // // - Client changes to filesystem state may be sent to the remote // filesystem asynchronously, except when server permission checks are // necessary. // // - File timestamps are based on client clocks. This ensures that users of // the client observe timestamps that are coherent with their own clocks // and consistent with Linux's semantics. However, since it is not always // possible for clients to set arbitrary atimes and mtimes, and never // possible for clients to set arbitrary ctimes, file timestamp changes are // stored in the client only and never sent to the remote filesystem. InteropModeExclusive InteropMode = iota // InteropModeWritethrough is appropriate when there are read-only users of // the remote filesystem that expect to observe changes made by the // filesystem client. // // - The client may cache arbitrary filesystem state. // // - Client changes to filesystem state must be sent to the remote // filesystem synchronously. // // - File timestamps are based on client clocks. As a corollary, access // timestamp changes from other remote filesystem users will not be visible // to the client. InteropModeWritethrough // InteropModeShared is appropriate when there are users of the remote // filesystem that may mutate its state other than the client. // // - The client must verify cached filesystem state before using it. // // - Client changes to filesystem state must be sent to the remote // filesystem synchronously. // // - File timestamps are based on server clocks. This is necessary to // ensure that timestamp changes are synchronized between remote filesystem // users. // // Note that the correctness of InteropModeShared depends on the server // correctly implementing 9P fids (i.e. each fid immutably represents a // single filesystem object), even in the presence of remote filesystem // mutations from other users. If this is violated, the behavior of the // client is undefined. InteropModeShared ) // Name implements vfs.FilesystemType.Name. func (FilesystemType) Name() string { return Name } // GetFilesystem implements vfs.FilesystemType.GetFilesystem. func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) { mfp := pgalloc.MemoryFileProviderFromContext(ctx) if mfp == nil { ctx.Warningf("gofer.FilesystemType.GetFilesystem: context does not provide a pgalloc.MemoryFileProvider") return nil, nil, syserror.EINVAL } mopts := vfs.GenericParseMountOptions(opts.Data) var fsopts filesystemOptions // Check that the transport is "fd". trans, ok := mopts["trans"] if !ok { ctx.Warningf("gofer.FilesystemType.GetFilesystem: transport must be specified as 'trans=fd'") return nil, nil, syserror.EINVAL } delete(mopts, "trans") if trans != "fd" { ctx.Warningf("gofer.FilesystemType.GetFilesystem: unsupported transport: trans=%s", trans) return nil, nil, syserror.EINVAL } // Check that read and write FDs are provided and identical. rfdstr, ok := mopts["rfdno"] if !ok { ctx.Warningf("gofer.FilesystemType.GetFilesystem: read FD must be specified as 'rfdno=<file descriptor>") return nil, nil, syserror.EINVAL } delete(mopts, "rfdno") rfd, err := strconv.Atoi(rfdstr) if err != nil { ctx.Warningf("gofer.FilesystemType.GetFilesystem: invalid read FD: rfdno=%s", rfdstr) return nil, nil, syserror.EINVAL } wfdstr, ok := mopts["wfdno"] if !ok { ctx.Warningf("gofer.FilesystemType.GetFilesystem: write FD must be specified as 'wfdno=<file descriptor>") return nil, nil, syserror.EINVAL } delete(mopts, "wfdno") wfd, err := strconv.Atoi(wfdstr) if err != nil { ctx.Warningf("gofer.FilesystemType.GetFilesystem: invalid write FD: wfdno=%s", wfdstr) return nil, nil, syserror.EINVAL } if rfd != wfd { ctx.Warningf("gofer.FilesystemType.GetFilesystem: read FD (%d) and write FD (%d) must be equal", rfd, wfd) return nil, nil, syserror.EINVAL } fsopts.fd = rfd // Get the attach name. fsopts.aname = "/" if aname, ok := mopts["aname"]; ok { delete(mopts, "aname") fsopts.aname = aname } // Parse the cache policy. For historical reasons, this defaults to the // least generally-applicable option, InteropModeExclusive. fsopts.interop = InteropModeExclusive if cache, ok := mopts["cache"]; ok { delete(mopts, "cache") switch cache { case "fscache": fsopts.interop = InteropModeExclusive case "fscache_writethrough": fsopts.interop = InteropModeWritethrough case "none": fsopts.regularFilesUseSpecialFileFD = true fallthrough case "remote_revalidating": fsopts.interop = InteropModeShared default: ctx.Warningf("gofer.FilesystemType.GetFilesystem: invalid cache policy: cache=%s", cache) return nil, nil, syserror.EINVAL } } // Parse the 9P message size. fsopts.msize = 1024 * 1024 // 1M, tested to give good enough performance up to 64M if msizestr, ok := mopts["msize"]; ok { delete(mopts, "msize") msize, err := strconv.ParseUint(msizestr, 10, 32) if err != nil { ctx.Warningf("gofer.FilesystemType.GetFilesystem: invalid message size: msize=%s", msizestr) return nil, nil, syserror.EINVAL } fsopts.msize = uint32(msize) } // Parse the 9P protocol version. fsopts.version = p9.HighestVersionString() if version, ok := mopts["version"]; ok { delete(mopts, "version") fsopts.version = version } // Parse the dentry cache limit. fsopts.maxCachedDentries = 1000 if str, ok := mopts["dentry_cache_limit"]; ok { delete(mopts, "dentry_cache_limit") maxCachedDentries, err := strconv.ParseUint(str, 10, 64) if err != nil { ctx.Warningf("gofer.FilesystemType.GetFilesystem: invalid dentry cache limit: dentry_cache_limit=%s", str) return nil, nil, syserror.EINVAL } fsopts.maxCachedDentries = maxCachedDentries } // Handle simple flags. if _, ok := mopts["force_page_cache"]; ok { delete(mopts, "force_page_cache") fsopts.forcePageCache = true } if _, ok := mopts["limit_host_fd_translation"]; ok { delete(mopts, "limit_host_fd_translation") fsopts.limitHostFDTranslation = true } if _, ok := mopts["overlayfs_stale_read"]; ok { delete(mopts, "overlayfs_stale_read") fsopts.overlayfsStaleRead = true } // fsopts.regularFilesUseSpecialFileFD can only be enabled by specifying // "cache=none". // Check for unparsed options. if len(mopts) != 0 { ctx.Warningf("gofer.FilesystemType.GetFilesystem: unknown options: %v", mopts) return nil, nil, syserror.EINVAL } // Establish a connection with the server. conn, err := unet.NewSocket(fsopts.fd) if err != nil { return nil, nil, err } // Perform version negotiation with the server. ctx.UninterruptibleSleepStart(false) client, err := p9.NewClient(conn, fsopts.msize, fsopts.version) ctx.UninterruptibleSleepFinish(false) if err != nil { conn.Close() return nil, nil, err } // Ownership of conn has been transferred to client. // Perform attach to obtain the filesystem root. ctx.UninterruptibleSleepStart(false) attached, err := client.Attach(fsopts.aname) ctx.UninterruptibleSleepFinish(false) if err != nil { client.Close() return nil, nil, err } attachFile := p9file{attached} qid, attrMask, attr, err := attachFile.getAttr(ctx, dentryAttrMask()) if err != nil { attachFile.close(ctx) client.Close() return nil, nil, err } // Construct the filesystem object. fs := &filesystem{ mfp: mfp, opts: fsopts, uid: creds.EffectiveKUID, gid: creds.EffectiveKGID, client: client, clock: ktime.RealtimeClockFromContext(ctx), dentries: make(map[*dentry]struct{}), specialFileFDs: make(map[*specialFileFD]struct{}), } fs.vfsfs.Init(vfsObj, &fstype, fs) // Construct the root dentry. root, err := fs.newDentry(ctx, attachFile, qid, attrMask, &attr) if err != nil { attachFile.close(ctx) fs.vfsfs.DecRef() return nil, nil, err } // Set the root's reference count to 2. One reference is returned to the // caller, and the other is deliberately leaked to prevent the root from // being "cached" and subsequently evicted. Its resources will still be // cleaned up by fs.Release(). root.refs = 2 return &fs.vfsfs, &root.vfsd, nil } // Release implements vfs.FilesystemImpl.Release. func (fs *filesystem) Release() { ctx := context.Background() mf := fs.mfp.MemoryFile() fs.syncMu.Lock() for d := range fs.dentries { d.handleMu.Lock() d.dataMu.Lock() if d.handleWritable { // Write dirty cached data to the remote file. if err := fsutil.SyncDirtyAll(ctx, &d.cache, &d.dirty, d.size, fs.mfp.MemoryFile(), d.handle.writeFromBlocksAt); err != nil { log.Warningf("gofer.filesystem.Release: failed to flush dentry: %v", err) } // TODO(jamieliu): Do we need to flushf/fsync d? } // Discard cached pages. d.cache.DropAll(mf) d.dirty.RemoveAll() d.dataMu.Unlock() // Close the host fd if one exists. if d.handle.fd >= 0 { syscall.Close(int(d.handle.fd)) d.handle.fd = -1 } d.handleMu.Unlock() } // There can't be any specialFileFDs still using fs, since each such // FileDescription would hold a reference on a Mount holding a reference on // fs. fs.syncMu.Unlock() // Close the connection to the server. This implicitly clunks all fids. fs.client.Close() } // dentry implements vfs.DentryImpl. type dentry struct { vfsd vfs.Dentry // refs is the reference count. Each dentry holds a reference on its // parent, even if disowned. refs is accessed using atomic memory // operations. When refs reaches 0, the dentry may be added to the cache or // destroyed. If refs==-1 the dentry has already been destroyed. refs int64 // fs is the owning filesystem. fs is immutable. fs *filesystem // parent is this dentry's parent directory. Each dentry holds a reference // on its parent. If this dentry is a filesystem root, parent is nil. // parent is protected by filesystem.renameMu. parent *dentry // name is the name of this dentry in its parent. If this dentry is a // filesystem root, name is the empty string. name is protected by // filesystem.renameMu. name string // We don't support hard links, so each dentry maps 1:1 to an inode. // file is the unopened p9.File that backs this dentry. file is immutable. file p9file // If deleted is non-zero, the file represented by this dentry has been // deleted. deleted is accessed using atomic memory operations. deleted uint32 // If cached is true, dentryEntry links dentry into // filesystem.cachedDentries. cached and dentryEntry are protected by // filesystem.renameMu. cached bool dentryEntry dirMu sync.Mutex // If this dentry represents a directory, children contains: // // - Mappings of child filenames to dentries representing those children. // // - Mappings of child filenames that are known not to exist to nil // dentries (only if InteropModeShared is not in effect). // // children is protected by dirMu. children map[string]*dentry // If this dentry represents a directory, InteropModeShared is not in // effect, and dirents is not nil, it is a cache of all entries in the // directory, in the order they were returned by the server. dirents is // protected by dirMu. dirents []vfs.Dirent // Cached metadata; protected by metadataMu and accessed using atomic // memory operations unless otherwise specified. metadataMu sync.Mutex ino uint64 // immutable mode uint32 // type is immutable, perms are mutable uid uint32 // auth.KUID, but stored as raw uint32 for sync/atomic gid uint32 // auth.KGID, but ... blockSize uint32 // 0 if unknown // Timestamps, all nsecs from the Unix epoch. atime int64 mtime int64 ctime int64 btime int64 // File size, protected by both metadataMu and dataMu (i.e. both must be // locked to mutate it). size uint64 // nlink counts the number of hard links to this dentry. It's updated and // accessed using atomic operations. It's not protected by metadataMu like the // other metadata fields. nlink uint32 mapsMu sync.Mutex // If this dentry represents a regular file, mappings tracks mappings of // the file into memmap.MappingSpaces. mappings is protected by mapsMu. mappings memmap.MappingSet // If this dentry represents a regular file or directory: // // - handle is the I/O handle used by all regularFileFDs/directoryFDs // representing this dentry. // // - handleReadable is true if handle is readable. // // - handleWritable is true if handle is writable. // // Invariants: // // - If handleReadable == handleWritable == false, then handle.file == nil // (i.e. there is no open handle). Conversely, if handleReadable || // handleWritable == true, then handle.file != nil (i.e. there is an open // handle). // // - handleReadable and handleWritable cannot transition from true to false // (i.e. handles may not be downgraded). // // These fields are protected by handleMu. handleMu sync.RWMutex handle handle handleReadable bool handleWritable bool dataMu sync.RWMutex // If this dentry represents a regular file that is client-cached, cache // maps offsets into the cached file to offsets into // filesystem.mfp.MemoryFile() that store the file's data. cache is // protected by dataMu. cache fsutil.FileRangeSet // If this dentry represents a regular file that is client-cached, dirty // tracks dirty segments in cache. dirty is protected by dataMu. dirty fsutil.DirtySet // pf implements platform.File for mappings of handle.fd. pf dentryPlatformFile // If this dentry represents a symbolic link, InteropModeShared is not in // effect, and haveTarget is true, target is the symlink target. haveTarget // and target are protected by dataMu. haveTarget bool target string } // dentryAttrMask returns a p9.AttrMask enabling all attributes used by the // gofer client. func dentryAttrMask() p9.AttrMask { return p9.AttrMask{ Mode: true, UID: true, GID: true, ATime: true, MTime: true, CTime: true, Size: true, BTime: true, } } // newDentry creates a new dentry representing the given file. The dentry // initially has no references, but is not cached; it is the caller's // responsibility to set the dentry's reference count and/or call // dentry.checkCachingLocked() as appropriate. func (fs *filesystem) newDentry(ctx context.Context, file p9file, qid p9.QID, mask p9.AttrMask, attr *p9.Attr) (*dentry, error) { if !mask.Mode { ctx.Warningf("can't create gofer.dentry without file type") return nil, syserror.EIO } if attr.Mode.FileType() == p9.ModeRegular && !mask.Size { ctx.Warningf("can't create regular file gofer.dentry without file size") return nil, syserror.EIO } d := &dentry{ fs: fs, file: file, ino: qid.Path, mode: uint32(attr.Mode), uid: uint32(fs.uid), gid: uint32(fs.gid), blockSize: usermem.PageSize, handle: handle{ fd: -1, }, } d.pf.dentry = d if mask.UID { d.uid = uint32(attr.UID) } if mask.GID { d.gid = uint32(attr.GID) } if mask.Size { d.size = attr.Size } if attr.BlockSize != 0 { d.blockSize = uint32(attr.BlockSize) } if mask.ATime { d.atime = dentryTimestampFromP9(attr.ATimeSeconds, attr.ATimeNanoSeconds) } if mask.MTime { d.mtime = dentryTimestampFromP9(attr.MTimeSeconds, attr.MTimeNanoSeconds) } if mask.CTime { d.ctime = dentryTimestampFromP9(attr.CTimeSeconds, attr.CTimeNanoSeconds) } if mask.BTime { d.btime = dentryTimestampFromP9(attr.BTimeSeconds, attr.BTimeNanoSeconds) } if mask.NLink { d.nlink = uint32(attr.NLink) } d.vfsd.Init(d) fs.syncMu.Lock() fs.dentries[d] = struct{}{} fs.syncMu.Unlock() return d, nil } // updateFromP9Attrs is called to update d's metadata after an update from the // remote filesystem. func (d *dentry) updateFromP9Attrs(mask p9.AttrMask, attr *p9.Attr) { d.metadataMu.Lock() if mask.Mode { if got, want := uint32(attr.Mode.FileType()), d.fileType(); got != want { d.metadataMu.Unlock() panic(fmt.Sprintf("gofer.dentry file type changed from %#o to %#o", want, got)) } atomic.StoreUint32(&d.mode, uint32(attr.Mode)) } if mask.UID { atomic.StoreUint32(&d.uid, uint32(attr.UID)) } if mask.GID { atomic.StoreUint32(&d.gid, uint32(attr.GID)) } // There is no P9_GETATTR_* bit for I/O block size. if attr.BlockSize != 0 { atomic.StoreUint32(&d.blockSize, uint32(attr.BlockSize)) } if mask.ATime { atomic.StoreInt64(&d.atime, dentryTimestampFromP9(attr.ATimeSeconds, attr.ATimeNanoSeconds)) } if mask.MTime { atomic.StoreInt64(&d.mtime, dentryTimestampFromP9(attr.MTimeSeconds, attr.MTimeNanoSeconds)) } if mask.CTime { atomic.StoreInt64(&d.ctime, dentryTimestampFromP9(attr.CTimeSeconds, attr.CTimeNanoSeconds)) } if mask.BTime { atomic.StoreInt64(&d.btime, dentryTimestampFromP9(attr.BTimeSeconds, attr.BTimeNanoSeconds)) } if mask.NLink { atomic.StoreUint32(&d.nlink, uint32(attr.NLink)) } if mask.Size { d.dataMu.Lock() atomic.StoreUint64(&d.size, attr.Size) d.dataMu.Unlock() } d.metadataMu.Unlock() } func (d *dentry) updateFromGetattr(ctx context.Context) error { // Use d.handle.file, which represents a 9P fid that has been opened, in // preference to d.file, which represents a 9P fid that has not. This may // be significantly more efficient in some implementations. var ( file p9file handleMuRLocked bool ) d.handleMu.RLock() if !d.handle.file.isNil() { file = d.handle.file handleMuRLocked = true } else { file = d.file d.handleMu.RUnlock() } _, attrMask, attr, err := file.getAttr(ctx, dentryAttrMask()) if handleMuRLocked { d.handleMu.RUnlock() } if err != nil { return err } d.updateFromP9Attrs(attrMask, &attr) return nil } func (d *dentry) fileType() uint32 { return atomic.LoadUint32(&d.mode) & linux.S_IFMT } func (d *dentry) statTo(stat *linux.Statx) { stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | linux.STATX_UID | linux.STATX_GID | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME | linux.STATX_INO | linux.STATX_SIZE | linux.STATX_BLOCKS | linux.STATX_BTIME stat.Blksize = atomic.LoadUint32(&d.blockSize) stat.Nlink = atomic.LoadUint32(&d.nlink) stat.UID = atomic.LoadUint32(&d.uid) stat.GID = atomic.LoadUint32(&d.gid) stat.Mode = uint16(atomic.LoadUint32(&d.mode)) stat.Ino = d.ino stat.Size = atomic.LoadUint64(&d.size) // This is consistent with regularFileFD.Seek(), which treats regular files // as having no holes. stat.Blocks = (stat.Size + 511) / 512 stat.Atime = statxTimestampFromDentry(atomic.LoadInt64(&d.atime)) stat.Btime = statxTimestampFromDentry(atomic.LoadInt64(&d.btime)) stat.Ctime = statxTimestampFromDentry(atomic.LoadInt64(&d.ctime)) stat.Mtime = statxTimestampFromDentry(atomic.LoadInt64(&d.mtime)) // TODO(gvisor.dev/issue/1198): device number } func (d *dentry) setStat(ctx context.Context, creds *auth.Credentials, stat *linux.Statx, mnt *vfs.Mount) error { if stat.Mask == 0 { return nil } if stat.Mask&^(linux.STATX_MODE|linux.STATX_UID|linux.STATX_GID|linux.STATX_ATIME|linux.STATX_MTIME|linux.STATX_SIZE) != 0 { return syserror.EPERM } mode := linux.FileMode(atomic.LoadUint32(&d.mode)) if err := vfs.CheckSetStat(ctx, creds, stat, mode, auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))); err != nil { return err } if err := mnt.CheckBeginWrite(); err != nil { return err } defer mnt.EndWrite() setLocalAtime := false setLocalMtime := false if d.fs.opts.interop != InteropModeShared { // Timestamp updates will be handled locally. setLocalAtime = stat.Mask&linux.STATX_ATIME != 0 setLocalMtime = stat.Mask&linux.STATX_MTIME != 0 stat.Mask &^= linux.STATX_ATIME | linux.STATX_MTIME if !setLocalMtime && (stat.Mask&linux.STATX_SIZE != 0) { // Truncate updates mtime. setLocalMtime = true stat.Mtime.Nsec = linux.UTIME_NOW } } d.metadataMu.Lock() defer d.metadataMu.Unlock() if stat.Mask != 0 { if err := d.file.setAttr(ctx, p9.SetAttrMask{ Permissions: stat.Mask&linux.STATX_MODE != 0, UID: stat.Mask&linux.STATX_UID != 0, GID: stat.Mask&linux.STATX_GID != 0, Size: stat.Mask&linux.STATX_SIZE != 0, ATime: stat.Mask&linux.STATX_ATIME != 0, MTime: stat.Mask&linux.STATX_MTIME != 0, ATimeNotSystemTime: stat.Atime.Nsec != linux.UTIME_NOW, MTimeNotSystemTime: stat.Mtime.Nsec != linux.UTIME_NOW, }, p9.SetAttr{ Permissions: p9.FileMode(stat.Mode), UID: p9.UID(stat.UID), GID: p9.GID(stat.GID), Size: stat.Size, ATimeSeconds: uint64(stat.Atime.Sec), ATimeNanoSeconds: uint64(stat.Atime.Nsec), MTimeSeconds: uint64(stat.Mtime.Sec), MTimeNanoSeconds: uint64(stat.Mtime.Nsec), }); err != nil { return err } } if d.fs.opts.interop == InteropModeShared { // There's no point to updating d's metadata in this case since it'll // be overwritten by revalidation before the next time it's used // anyway. (InteropModeShared inhibits client caching of regular file // data, so there's no cache to truncate either.) return nil } now := d.fs.clock.Now().Nanoseconds() if stat.Mask&linux.STATX_MODE != 0 { atomic.StoreUint32(&d.mode, d.fileType()|uint32(stat.Mode)) } if stat.Mask&linux.STATX_UID != 0 { atomic.StoreUint32(&d.uid, stat.UID) } if stat.Mask&linux.STATX_GID != 0 { atomic.StoreUint32(&d.gid, stat.GID) } if setLocalAtime { if stat.Atime.Nsec == linux.UTIME_NOW { atomic.StoreInt64(&d.atime, now) } else { atomic.StoreInt64(&d.atime, dentryTimestampFromStatx(stat.Atime)) } } if setLocalMtime { if stat.Mtime.Nsec == linux.UTIME_NOW { atomic.StoreInt64(&d.mtime, now) } else { atomic.StoreInt64(&d.mtime, dentryTimestampFromStatx(stat.Mtime)) } } atomic.StoreInt64(&d.ctime, now) if stat.Mask&linux.STATX_SIZE != 0 { d.dataMu.Lock() oldSize := d.size d.size = stat.Size // d.dataMu must be unlocked to lock d.mapsMu and invalidate mappings // below. This allows concurrent calls to Read/Translate/etc. These // functions synchronize with truncation by refusing to use cache // contents beyond the new d.size. (We are still holding d.metadataMu, // so we can't race with Write or another truncate.) d.dataMu.Unlock() if d.size < oldSize { oldpgend := pageRoundUp(oldSize) newpgend := pageRoundUp(d.size) if oldpgend != newpgend { d.mapsMu.Lock() d.mappings.Invalidate(memmap.MappableRange{newpgend, oldpgend}, memmap.InvalidateOpts{ // Compare Linux's mm/truncate.c:truncate_setsize() => // truncate_pagecache() => // mm/memory.c:unmap_mapping_range(evencows=1). InvalidatePrivate: true, }) d.mapsMu.Unlock() } // We are now guaranteed that there are no translations of // truncated pages, and can remove them from the cache. Since // truncated pages have been removed from the remote file, they // should be dropped without being written back. d.dataMu.Lock() d.cache.Truncate(d.size, d.fs.mfp.MemoryFile()) d.dirty.KeepClean(memmap.MappableRange{d.size, oldpgend}) d.dataMu.Unlock() } } return nil } func (d *dentry) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes) error { return vfs.GenericCheckPermissions(creds, ats, linux.FileMode(atomic.LoadUint32(&d.mode)), auth.KUID(atomic.LoadUint32(&d.uid)), auth.KGID(atomic.LoadUint32(&d.gid))) } // IncRef implements vfs.DentryImpl.IncRef. func (d *dentry) IncRef() { // d.refs may be 0 if d.fs.renameMu is locked, which serializes against // d.checkCachingLocked(). atomic.AddInt64(&d.refs, 1) } // TryIncRef implements vfs.DentryImpl.TryIncRef. func (d *dentry) TryIncRef() bool { for { refs := atomic.LoadInt64(&d.refs) if refs <= 0 { return false } if atomic.CompareAndSwapInt64(&d.refs, refs, refs+1) { return true } } } // DecRef implements vfs.DentryImpl.DecRef. func (d *dentry) DecRef() { if refs := atomic.AddInt64(&d.refs, -1); refs == 0 { d.fs.renameMu.Lock() d.checkCachingLocked() d.fs.renameMu.Unlock() } else if refs < 0 { panic("gofer.dentry.DecRef() called without holding a reference") } } // checkCachingLocked should be called after d's reference count becomes 0 or it // becomes disowned. // // It may be called on a destroyed dentry. For example, // renameMu[R]UnlockAndCheckCaching may call checkCachingLocked multiple times // for the same dentry when the dentry is visited more than once in the same // operation. One of the calls may destroy the dentry, so subsequent calls will // do nothing. // // Preconditions: d.fs.renameMu must be locked for writing. func (d *dentry) checkCachingLocked() { // Dentries with a non-zero reference count must be retained. (The only way // to obtain a reference on a dentry with zero references is via path // resolution, which requires renameMu, so if d.refs is zero then it will // remain zero while we hold renameMu for writing.) refs := atomic.LoadInt64(&d.refs) if refs > 0 { if d.cached { d.fs.cachedDentries.Remove(d) d.fs.cachedDentriesLen-- d.cached = false } return } if refs == -1 { // Dentry has already been destroyed. return } // Deleted and invalidated dentries with zero references are no longer // reachable by path resolution and should be dropped immediately. if d.vfsd.IsDead() { if d.cached { d.fs.cachedDentries.Remove(d) d.fs.cachedDentriesLen-- d.cached = false } d.destroyLocked() return } // If d is already cached, just move it to the front of the LRU. if d.cached { d.fs.cachedDentries.Remove(d) d.fs.cachedDentries.PushFront(d) return } // Cache the dentry, then evict the least recently used cached dentry if // the cache becomes over-full. d.fs.cachedDentries.PushFront(d) d.fs.cachedDentriesLen++ d.cached = true if d.fs.cachedDentriesLen > d.fs.opts.maxCachedDentries { victim := d.fs.cachedDentries.Back() d.fs.cachedDentries.Remove(victim) d.fs.cachedDentriesLen-- victim.cached = false // victim.refs may have become non-zero from an earlier path resolution // since it was inserted into fs.cachedDentries. if atomic.LoadInt64(&victim.refs) == 0 { if victim.parent != nil { victim.parent.dirMu.Lock() if !victim.vfsd.IsDead() { // Note that victim can't be a mount point (in any mount // namespace), since VFS holds references on mount points. d.fs.vfsfs.VirtualFilesystem().InvalidateDentry(&victim.vfsd) delete(victim.parent.children, victim.name) // We're only deleting the dentry, not the file it // represents, so we don't need to update // victimParent.dirents etc. } victim.parent.dirMu.Unlock() } victim.destroyLocked() } // Whether or not victim was destroyed, we brought fs.cachedDentriesLen // back down to fs.opts.maxCachedDentries, so we don't loop. } } // destroyLocked destroys the dentry. It may flushes dirty pages from cache, // close p9 file and remove reference on parent dentry. // // Preconditions: d.fs.renameMu must be locked for writing. d.refs == 0. d is // not a child dentry. func (d *dentry) destroyLocked() { switch atomic.LoadInt64(&d.refs) { case 0: // Mark the dentry destroyed. atomic.StoreInt64(&d.refs, -1) case -1: panic("dentry.destroyLocked() called on already destroyed dentry") default: panic("dentry.destroyLocked() called with references on the dentry") } ctx := context.Background() d.handleMu.Lock() if !d.handle.file.isNil() { mf := d.fs.mfp.MemoryFile() d.dataMu.Lock() // Write dirty pages back to the remote filesystem. if d.handleWritable { if err := fsutil.SyncDirtyAll(ctx, &d.cache, &d.dirty, d.size, mf, d.handle.writeFromBlocksAt); err != nil { log.Warningf("gofer.dentry.DecRef: failed to write dirty data back: %v", err) } } // Discard cached data. d.cache.DropAll(mf) d.dirty.RemoveAll() d.dataMu.Unlock() // Clunk open fids and close open host FDs. d.handle.close(ctx) } d.handleMu.Unlock() if !d.file.isNil() { d.file.close(ctx) d.file = p9file{} } // Remove d from the set of all dentries. d.fs.syncMu.Lock() delete(d.fs.dentries, d) d.fs.syncMu.Unlock() // Drop the reference held by d on its parent without recursively locking // d.fs.renameMu. if d.parent != nil { if refs := atomic.AddInt64(&d.parent.refs, -1); refs == 0 { d.parent.checkCachingLocked() } else if refs < 0 { panic("gofer.dentry.DecRef() called without holding a reference") } } } func (d *dentry) isDeleted() bool { return atomic.LoadUint32(&d.deleted) != 0 } func (d *dentry) setDeleted() { atomic.StoreUint32(&d.deleted, 1) } // We only support xattrs prefixed with "user." (see b/148380782). Currently, // there is no need to expose any other xattrs through a gofer. func (d *dentry) listxattr(ctx context.Context, creds *auth.Credentials, size uint64) ([]string, error) { xattrMap, err := d.file.listXattr(ctx, size) if err != nil { return nil, err } xattrs := make([]string, 0, len(xattrMap)) for x := range xattrMap { if strings.HasPrefix(x, linux.XATTR_USER_PREFIX) { xattrs = append(xattrs, x) } } return xattrs, nil } func (d *dentry) getxattr(ctx context.Context, creds *auth.Credentials, opts *vfs.GetxattrOptions) (string, error) { if err := d.checkPermissions(creds, vfs.MayRead); err != nil { return "", err } if !strings.HasPrefix(opts.Name, linux.XATTR_USER_PREFIX) { return "", syserror.EOPNOTSUPP } return d.file.getXattr(ctx, opts.Name, opts.Size) } func (d *dentry) setxattr(ctx context.Context, creds *auth.Credentials, opts *vfs.SetxattrOptions) error { if err := d.checkPermissions(creds, vfs.MayWrite); err != nil { return err } if !strings.HasPrefix(opts.Name, linux.XATTR_USER_PREFIX) { return syserror.EOPNOTSUPP } return d.file.setXattr(ctx, opts.Name, opts.Value, opts.Flags) } func (d *dentry) removexattr(ctx context.Context, creds *auth.Credentials, name string) error { if err := d.checkPermissions(creds, vfs.MayWrite); err != nil { return err } if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) { return syserror.EOPNOTSUPP } return d.file.removeXattr(ctx, name) } // Preconditions: d.isRegularFile() || d.isDirectory(). func (d *dentry) ensureSharedHandle(ctx context.Context, read, write, trunc bool) error { // O_TRUNC unconditionally requires us to obtain a new handle (opened with // O_TRUNC). if !trunc { d.handleMu.RLock() if (!read || d.handleReadable) && (!write || d.handleWritable) { // The current handle is sufficient. d.handleMu.RUnlock() return nil } d.handleMu.RUnlock() } haveOldFD := false d.handleMu.Lock() if (read && !d.handleReadable) || (write && !d.handleWritable) || trunc { // Get a new handle. wantReadable := d.handleReadable || read wantWritable := d.handleWritable || write h, err := openHandle(ctx, d.file, wantReadable, wantWritable, trunc) if err != nil { d.handleMu.Unlock() return err } if !d.handle.file.isNil() { // Check that old and new handles are compatible: If the old handle // includes a host file descriptor but the new one does not, or // vice versa, old and new memory mappings may be incoherent. haveOldFD = d.handle.fd >= 0 haveNewFD := h.fd >= 0 if haveOldFD != haveNewFD { d.handleMu.Unlock() ctx.Warningf("gofer.dentry.ensureSharedHandle: can't change host FD availability from %v to %v across dentry handle upgrade", haveOldFD, haveNewFD) h.close(ctx) return syserror.EIO } if haveOldFD { // We may have raced with callers of d.pf.FD() that are now // using the old file descriptor, preventing us from safely // closing it. We could handle this by invalidating existing // memmap.Translations, but this is expensive. Instead, use // dup3 to make the old file descriptor refer to the new file // description, then close the new file descriptor (which is no // longer needed). Racing callers may use the old or new file // description, but this doesn't matter since they refer to the // same file (unless d.fs.opts.overlayfsStaleRead is true, // which we handle separately). if err := syscall.Dup3(int(h.fd), int(d.handle.fd), syscall.O_CLOEXEC); err != nil { d.handleMu.Unlock() ctx.Warningf("gofer.dentry.ensureSharedHandle: failed to dup fd %d to fd %d: %v", h.fd, d.handle.fd, err) h.close(ctx) return err } syscall.Close(int(h.fd)) h.fd = d.handle.fd if d.fs.opts.overlayfsStaleRead { // Replace sentry mappings of the old FD with mappings of // the new FD, since the two are not necessarily coherent. if err := d.pf.hostFileMapper.RegenerateMappings(int(h.fd)); err != nil { d.handleMu.Unlock() ctx.Warningf("gofer.dentry.ensureSharedHandle: failed to replace sentry mappings of old FD with mappings of new FD: %v", err) h.close(ctx) return err } } // Clunk the old fid before making the new handle visible (by // unlocking d.handleMu). d.handle.file.close(ctx) } } // Switch to the new handle. d.handle = h d.handleReadable = wantReadable d.handleWritable = wantWritable } d.handleMu.Unlock() if d.fs.opts.overlayfsStaleRead && haveOldFD { // Invalidate application mappings that may be using the old FD; they // will be replaced with mappings using the new FD after future calls // to d.Translate(). This requires holding d.mapsMu, which precedes // d.handleMu in the lock order. d.mapsMu.Lock() d.mappings.InvalidateAll(memmap.InvalidateOpts{}) d.mapsMu.Unlock() } return nil } // incLinks increments link count. // // Preconditions: d.nlink != 0 && d.nlink < math.MaxUint32. func (d *dentry) incLinks() { v := atomic.AddUint32(&d.nlink, 1) if v < 2 { panic(fmt.Sprintf("dentry.nlink is invalid (was 0 or overflowed): %d", v)) } } // decLinks decrements link count. // // Preconditions: d.nlink > 1. func (d *dentry) decLinks() { v := atomic.AddUint32(&d.nlink, ^uint32(0)) if v == 0 { panic(fmt.Sprintf("dentry.nlink must be greater than 0: %d", v)) } } // fileDescription is embedded by gofer implementations of // vfs.FileDescriptionImpl. type fileDescription struct { vfsfd vfs.FileDescription vfs.FileDescriptionDefaultImpl } func (fd *fileDescription) filesystem() *filesystem { return fd.vfsfd.Mount().Filesystem().Impl().(*filesystem) } func (fd *fileDescription) dentry() *dentry { return fd.vfsfd.Dentry().Impl().(*dentry) } // Stat implements vfs.FileDescriptionImpl.Stat. func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linux.Statx, error) { d := fd.dentry() const validMask = uint32(linux.STATX_MODE | linux.STATX_UID | linux.STATX_GID | linux.STATX_ATIME | linux.STATX_MTIME | linux.STATX_CTIME | linux.STATX_SIZE | linux.STATX_BLOCKS | linux.STATX_BTIME) if d.fs.opts.interop == InteropModeShared && opts.Mask&(validMask) != 0 && opts.Sync != linux.AT_STATX_DONT_SYNC { // TODO(jamieliu): Use specialFileFD.handle.file for the getattr if // available? if err := d.updateFromGetattr(ctx); err != nil { return linux.Statx{}, err } } var stat linux.Statx d.statTo(&stat) return stat, nil } // SetStat implements vfs.FileDescriptionImpl.SetStat. func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions) error { return fd.dentry().setStat(ctx, auth.CredentialsFromContext(ctx), &opts.Stat, fd.vfsfd.Mount()) } // Listxattr implements vfs.FileDescriptionImpl.Listxattr. func (fd *fileDescription) Listxattr(ctx context.Context, size uint64) ([]string, error) { return fd.dentry().listxattr(ctx, auth.CredentialsFromContext(ctx), size) } // Getxattr implements vfs.FileDescriptionImpl.Getxattr. func (fd *fileDescription) Getxattr(ctx context.Context, opts vfs.GetxattrOptions) (string, error) { return fd.dentry().getxattr(ctx, auth.CredentialsFromContext(ctx), &opts) } // Setxattr implements vfs.FileDescriptionImpl.Setxattr. func (fd *fileDescription) Setxattr(ctx context.Context, opts vfs.SetxattrOptions) error { return fd.dentry().setxattr(ctx, auth.CredentialsFromContext(ctx), &opts) } // Removexattr implements vfs.FileDescriptionImpl.Removexattr. func (fd *fileDescription) Removexattr(ctx context.Context, name string) error { return fd.dentry().removexattr(ctx, auth.CredentialsFromContext(ctx), name) }