diff options
author | Jamie Liu <jamieliu@google.com> | 2020-04-21 12:16:42 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2020-04-21 12:18:07 -0700 |
commit | 9b5e305e05ef3ad51778981062d6152cea1cd4fb (patch) | |
tree | 7fa4a4f665e482efd9435ef7b0df2ccce505c70a /pkg/sentry/fsimpl/ext | |
parent | 639c8dd80870133f61465588e717b725417a0c41 (diff) |
Remove filesystem structure from vfs.Dentry.
This change:
- Drastically simplifies the synchronization model: filesystem structure is
both implementation-defined and implementation-synchronized.
- Allows implementations of vfs.DentryImpl to use implementation-specific
dentry types, reducing casts during path traversal.
- Doesn't require dentries representing non-directory files to waste space on a
map of children.
- Allows dentry revalidation and mount lookup to be correctly ordered (fixed
FIXME in fsimpl/gofer/filesystem.go).
- Removes the need to have two separate maps in gofer.dentry
(dentry.vfsd.children and dentry.negativeChildren) for positive and negative
lookups respectively.
//pkg/sentry/fsimpl/tmpfs/benchmark_test.go:
name old time/op new time/op delta
VFS2TmpfsStat/1-112 172ns ± 4% 165ns ± 3% -4.08% (p=0.002 n=9+9)
VFS2TmpfsStat/2-112 199ns ± 3% 195ns ±10% ~ (p=0.132 n=8+9)
VFS2TmpfsStat/3-112 230ns ± 2% 216ns ± 2% -6.15% (p=0.000 n=8+8)
VFS2TmpfsStat/8-112 390ns ± 2% 358ns ± 4% -8.33% (p=0.000 n=9+8)
VFS2TmpfsStat/64-112 2.20µs ± 3% 2.01µs ± 3% -8.48% (p=0.000 n=10+8)
VFS2TmpfsStat/100-112 3.42µs ± 9% 3.08µs ± 2% -9.82% (p=0.000 n=9+8)
VFS2TmpfsMountStat/1-112 278ns ± 1% 286ns ±15% ~ (p=0.712 n=8+10)
VFS2TmpfsMountStat/2-112 311ns ± 4% 298ns ± 2% -4.27% (p=0.000 n=9+8)
VFS2TmpfsMountStat/3-112 339ns ± 3% 330ns ± 9% ~ (p=0.070 n=8+9)
VFS2TmpfsMountStat/8-112 503ns ± 3% 466ns ± 3% -7.38% (p=0.000 n=8+8)
VFS2TmpfsMountStat/64-112 2.53µs ±16% 2.17µs ± 7% -14.19% (p=0.000 n=10+9)
VFS2TmpfsMountStat/100-112 3.60µs ± 4% 3.30µs ± 8% -8.33% (p=0.001 n=8+9)
Updates #1035
PiperOrigin-RevId: 307655892
Diffstat (limited to 'pkg/sentry/fsimpl/ext')
-rw-r--r-- | pkg/sentry/fsimpl/ext/BUILD | 12 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/ext/dentry.go | 4 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/ext/directory.go | 21 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/ext/filesystem.go | 54 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/ext/inode.go | 2 |
5 files changed, 65 insertions, 28 deletions
diff --git a/pkg/sentry/fsimpl/ext/BUILD b/pkg/sentry/fsimpl/ext/BUILD index d83d75b3d..a4947c480 100644 --- a/pkg/sentry/fsimpl/ext/BUILD +++ b/pkg/sentry/fsimpl/ext/BUILD @@ -15,6 +15,17 @@ go_template_instance( }, ) +go_template_instance( + name = "fstree", + out = "fstree.go", + package = "ext", + prefix = "generic", + template = "//pkg/sentry/vfs/genericfstree:generic_fstree", + types = { + "Dentry": "dentry", + }, +) + go_library( name = "ext", srcs = [ @@ -26,6 +37,7 @@ go_library( "extent_file.go", "file_description.go", "filesystem.go", + "fstree.go", "inode.go", "regular_file.go", "symlink.go", diff --git a/pkg/sentry/fsimpl/ext/dentry.go b/pkg/sentry/fsimpl/ext/dentry.go index a080cb189..bfbd7c3d4 100644 --- a/pkg/sentry/fsimpl/ext/dentry.go +++ b/pkg/sentry/fsimpl/ext/dentry.go @@ -22,6 +22,10 @@ import ( type dentry struct { vfsd vfs.Dentry + // Protected by filesystem.mu. + parent *dentry + name string + // inode is the inode represented by this dentry. Multiple Dentries may // share a single non-directory Inode (with hard links). inode is // immutable. diff --git a/pkg/sentry/fsimpl/ext/directory.go b/pkg/sentry/fsimpl/ext/directory.go index bd6ede995..12b875c8f 100644 --- a/pkg/sentry/fsimpl/ext/directory.go +++ b/pkg/sentry/fsimpl/ext/directory.go @@ -21,7 +21,6 @@ import ( "gvisor.dev/gvisor/pkg/log" "gvisor.dev/gvisor/pkg/sentry/fs" "gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout" - "gvisor.dev/gvisor/pkg/sentry/memmap" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" @@ -31,6 +30,10 @@ import ( type directory struct { inode inode + // childCache maps filenames to dentries for children for which dentries + // have been instantiated. childCache is protected by filesystem.mu. + childCache map[string]*dentry + // mu serializes the changes to childList. // Lock Order (outermost locks must be taken first): // directory.mu @@ -50,9 +53,13 @@ type directory struct { childMap map[string]*dirent } -// newDirectroy is the directory constructor. -func newDirectroy(inode inode, newDirent bool) (*directory, error) { - file := &directory{inode: inode, childMap: make(map[string]*dirent)} +// newDirectory is the directory constructor. +func newDirectory(inode inode, newDirent bool) (*directory, error) { + file := &directory{ + inode: inode, + childCache: make(map[string]*dentry), + childMap: make(map[string]*dirent), + } file.inode.impl = file // Initialize childList by reading dirents from the underlying file. @@ -299,9 +306,3 @@ func (fd *directoryFD) Seek(ctx context.Context, offset int64, whence int32) (in fd.off = offset return offset, nil } - -// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap. -func (fd *directoryFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error { - // mmap(2) specifies that EACCESS should be returned for non-regular file fds. - return syserror.EACCES -} diff --git a/pkg/sentry/fsimpl/ext/filesystem.go b/pkg/sentry/fsimpl/ext/filesystem.go index afea58f65..2c22a04af 100644 --- a/pkg/sentry/fsimpl/ext/filesystem.go +++ b/pkg/sentry/fsimpl/ext/filesystem.go @@ -89,14 +89,33 @@ func stepLocked(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, inode *inode, write boo } for { - nextVFSD, err := rp.ResolveComponent(vfsd) - if err != nil { - return nil, nil, err + name := rp.Component() + if name == "." { + rp.Advance() + return vfsd, inode, nil } - if nextVFSD == nil { - // Since the Dentry tree is not the sole source of truth for extfs, if it's - // not in the Dentry tree, it might need to be pulled from disk. - childDirent, ok := inode.impl.(*directory).childMap[rp.Component()] + d := vfsd.Impl().(*dentry) + if name == ".." { + isRoot, err := rp.CheckRoot(vfsd) + if err != nil { + return nil, nil, err + } + if isRoot || d.parent == nil { + rp.Advance() + return vfsd, inode, nil + } + if err := rp.CheckMount(&d.parent.vfsd); err != nil { + return nil, nil, err + } + rp.Advance() + return &d.parent.vfsd, d.parent.inode, nil + } + + dir := inode.impl.(*directory) + child, ok := dir.childCache[name] + if !ok { + // We may need to instantiate a new dentry for this child. + childDirent, ok := dir.childMap[name] if !ok { // The underlying inode does not exist on disk. return nil, nil, syserror.ENOENT @@ -115,21 +134,22 @@ func stepLocked(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, inode *inode, write boo } // incRef because this is being added to the dentry tree. childInode.incRef() - child := newDentry(childInode) - vfsd.InsertChild(&child.vfsd, rp.Component()) - - // Continue as usual now that nextVFSD is not nil. - nextVFSD = &child.vfsd + child = newDentry(childInode) + child.parent = d + child.name = name + dir.childCache[name] = child + } + if err := rp.CheckMount(&child.vfsd); err != nil { + return nil, nil, err } - nextInode := nextVFSD.Impl().(*dentry).inode - if nextInode.isSymlink() && rp.ShouldFollowSymlink() { - if err := rp.HandleSymlink(inode.impl.(*symlink).target); err != nil { + if child.inode.isSymlink() && rp.ShouldFollowSymlink() { + if err := rp.HandleSymlink(child.inode.impl.(*symlink).target); err != nil { return nil, nil, err } continue } rp.Advance() - return nextVFSD, nextInode, nil + return &child.vfsd, child.inode, nil } } @@ -515,5 +535,5 @@ func (fs *filesystem) RemovexattrAt(ctx context.Context, rp *vfs.ResolvingPath, func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDentry, b *fspath.Builder) error { fs.mu.RLock() defer fs.mu.RUnlock() - return vfs.GenericPrependPath(vfsroot, vd, b) + return genericPrependPath(vfsroot, vd.Mount(), vd.Dentry().Impl().(*dentry), b) } diff --git a/pkg/sentry/fsimpl/ext/inode.go b/pkg/sentry/fsimpl/ext/inode.go index a39a37318..a98512350 100644 --- a/pkg/sentry/fsimpl/ext/inode.go +++ b/pkg/sentry/fsimpl/ext/inode.go @@ -136,7 +136,7 @@ func newInode(fs *filesystem, inodeNum uint32) (*inode, error) { } return &f.inode, nil case linux.ModeDirectory: - f, err := newDirectroy(inode, fs.sb.IncompatibleFeatures().DirentFileType) + f, err := newDirectory(inode, fs.sb.IncompatibleFeatures().DirentFileType) if err != nil { return nil, err } |