diff options
Diffstat (limited to 'pkg/sentry/fsimpl/tmpfs/tmpfs.go')
| -rwxr-xr-x | pkg/sentry/fsimpl/tmpfs/tmpfs.go | 82 |
1 files changed, 45 insertions, 37 deletions
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go index 82c709b43..efc931468 100755 --- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go +++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go @@ -12,16 +12,19 @@ // See the License for the specific language governing permissions and // limitations under the License. -// Package tmpfs provides a filesystem implementation that behaves like tmpfs: -// the Dentry tree is the sole source of truth for the state of the filesystem. +// Package tmpfs provides an in-memory filesystem whose contents are +// application-mutable, consistent with Linux's tmpfs. // // Lock order: // // filesystem.mu // inode.mu // regularFileFD.offMu +// *** "memmap.Mappable locks" below this point // regularFile.mapsMu +// *** "memmap.Mappable locks taken by Translate" below this point // regularFile.dataMu +// directory.iterMu package tmpfs import ( @@ -41,6 +44,7 @@ import ( "gvisor.dev/gvisor/pkg/sentry/vfs/memxattr" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/usermem" ) // Name is the default filesystem name. @@ -112,18 +116,18 @@ func (fstype FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt fs.vfsfs.Init(vfsObj, newFSType, &fs) - var root *inode + var root *dentry switch rootFileType { case linux.S_IFREG: - root = fs.newRegularFile(creds, 0777) + root = fs.newDentry(fs.newRegularFile(creds, 0777)) case linux.S_IFLNK: - root = fs.newSymlink(creds, tmpfsOpts.RootSymlinkTarget) + root = fs.newDentry(fs.newSymlink(creds, tmpfsOpts.RootSymlinkTarget)) case linux.S_IFDIR: - root = fs.newDirectory(creds, 01777) + root = &fs.newDirectory(creds, 01777).dentry default: return nil, nil, fmt.Errorf("invalid tmpfs root file type: %#o", rootFileType) } - return &fs.vfsfs, &fs.newDentry(root).vfsd, nil + return &fs.vfsfs, &root.vfsd, nil } // Release implements vfs.FilesystemImpl.Release. @@ -134,20 +138,29 @@ func (fs *filesystem) Release() { type dentry struct { vfsd vfs.Dentry + // parent is this dentry's parent directory. Each referenced dentry holds a + // reference on parent.dentry. If this dentry is a filesystem root, parent + // is nil. parent is protected by filesystem.mu. + 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.mu. + name string + + // dentryEntry (ugh) links dentries into their parent directory.childList. + dentryEntry + // inode is the inode represented by this dentry. Multiple Dentries may // share a single non-directory inode (with hard links). inode is // immutable. - inode *inode - + // // tmpfs doesn't count references on dentries; because the dentry tree is // the sole source of truth, it is by definition always consistent with the // state of the filesystem. However, it does count references on inodes, // because inode resources are released when all references are dropped. - // (tmpfs doesn't really have resources to release, but we implement - // reference counting because tmpfs regular files will.) - - // dentryEntry (ugh) links dentries into their parent directory.childList. - dentryEntry + // dentry therefore forwards reference counting directly to inode. + inode *inode } func (fs *filesystem) newDentry(inode *inode) *dentry { @@ -207,10 +220,6 @@ type inode struct { ctime int64 // nanoseconds mtime int64 // nanoseconds - // Only meaningful for device special files. - rdevMajor uint32 - rdevMinor uint32 - // Advisory file locks, which lock at the inode level. locks lock.FileLocks @@ -230,7 +239,7 @@ func (i *inode) init(impl interface{}, fs *filesystem, creds *auth.Credentials, i.gid = uint32(creds.EffectiveKGID) i.ino = atomic.AddUint64(&fs.nextInoMinusOne, 1) // Tmpfs creation sets atime, ctime, and mtime to current time. - now := i.clock.Now().Nanoseconds() + now := fs.clock.Now().Nanoseconds() i.atime = now i.ctime = now i.mtime = now @@ -283,14 +292,10 @@ func (i *inode) tryIncRef() bool { func (i *inode) decRef() { if refs := atomic.AddInt64(&i.refs, -1); refs == 0 { if regFile, ok := i.impl.(*regularFile); ok { - // Hold inode.mu and regFile.dataMu while mutating - // size. - i.mu.Lock() - regFile.dataMu.Lock() + // Release memory used by regFile to store data. Since regFile is + // no longer usable, we don't need to grab any locks or update any + // metadata. regFile.data.DropAll(regFile.memFile) - atomic.StoreUint64(®File.size, 0) - regFile.dataMu.Unlock() - i.mu.Unlock() } } else if refs < 0 { panic("tmpfs.inode.decRef() called without holding a reference") @@ -310,15 +315,15 @@ func (i *inode) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes) e // a concurrent modification), so we do not require holding inode.mu. func (i *inode) statTo(stat *linux.Statx) { stat.Mask = linux.STATX_TYPE | linux.STATX_MODE | linux.STATX_NLINK | - linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_ATIME | - linux.STATX_BTIME | linux.STATX_CTIME | linux.STATX_MTIME - stat.Blksize = 1 // usermem.PageSize in tmpfs + linux.STATX_UID | linux.STATX_GID | linux.STATX_INO | linux.STATX_SIZE | + linux.STATX_BLOCKS | linux.STATX_ATIME | linux.STATX_CTIME | + linux.STATX_MTIME + stat.Blksize = usermem.PageSize stat.Nlink = atomic.LoadUint32(&i.nlink) stat.UID = atomic.LoadUint32(&i.uid) stat.GID = atomic.LoadUint32(&i.gid) stat.Mode = uint16(atomic.LoadUint32(&i.mode)) stat.Ino = i.ino - // Linux's tmpfs has no concept of btime, so zero-value is returned. stat.Atime = linux.NsecToStatxTimestamp(i.atime) stat.Ctime = linux.NsecToStatxTimestamp(i.ctime) stat.Mtime = linux.NsecToStatxTimestamp(i.mtime) @@ -327,19 +332,22 @@ func (i *inode) statTo(stat *linux.Statx) { case *regularFile: stat.Mask |= linux.STATX_SIZE | linux.STATX_BLOCKS stat.Size = uint64(atomic.LoadUint64(&impl.size)) - // In tmpfs, this will be FileRangeSet.Span() / 512 (but also cached in - // a uint64 accessed using atomic memory operations to avoid taking - // locks). + // TODO(jamieliu): This should be impl.data.Span() / 512, but this is + // too expensive to compute here. Cache it in regularFile. stat.Blocks = allocatedBlocksForSize(stat.Size) + case *directory: + // "20" is mm/shmem.c:BOGO_DIRENT_SIZE. + stat.Size = 20 * (2 + uint64(atomic.LoadInt64(&impl.numChildren))) + // stat.Blocks is 0. case *symlink: - stat.Mask |= linux.STATX_SIZE | linux.STATX_BLOCKS stat.Size = uint64(len(impl.target)) - stat.Blocks = allocatedBlocksForSize(stat.Size) + // stat.Blocks is 0. + case *namedPipe, *socketFile: + // stat.Size and stat.Blocks are 0. case *deviceFile: + // stat.Size and stat.Blocks are 0. stat.RdevMajor = impl.major stat.RdevMinor = impl.minor - case *socketFile, *directory, *namedPipe: - // Nothing to do. default: panic(fmt.Sprintf("unknown inode type: %T", i.impl)) } |