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-rw-r--r--pkg/sentry/fsimpl/gofer/gofer.go11
-rw-r--r--pkg/sentry/fsimpl/kernfs/BUILD26
-rw-r--r--pkg/sentry/fsimpl/kernfs/kernfs.go196
-rw-r--r--pkg/sentry/fsimpl/proc/filesystem.go22
-rw-r--r--pkg/sentry/fsimpl/sys/sys.go22
5 files changed, 226 insertions, 51 deletions
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 604c6d7cd..80668ebc1 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -153,8 +153,7 @@ type filesystemOptions struct {
msize uint32
version string
- // maxCachedDentries is the maximum number of dentries with 0 references
- // retained by the client.
+ // maxCachedDentries is the maximum size of filesystem.cachedDentries.
maxCachedDentries uint64
// If forcePageCache is true, host FDs may not be used for application
@@ -1312,6 +1311,10 @@ func (d *dentry) checkCachingLocked(ctx context.Context) {
// 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 == -1 {
+ // Dentry has already been destroyed.
+ return
+ }
if refs > 0 {
if d.cached {
d.fs.cachedDentries.Remove(d)
@@ -1320,10 +1323,6 @@ func (d *dentry) checkCachingLocked(ctx context.Context) {
}
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() {
diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index 4de1e6922..aaad67ab8 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -4,6 +4,18 @@ load("//tools/go_generics:defs.bzl", "go_template_instance")
licenses(["notice"])
go_template_instance(
+ name = "dentry_list",
+ out = "dentry_list.go",
+ package = "kernfs",
+ prefix = "dentry",
+ template = "//pkg/ilist:generic_list",
+ types = {
+ "Element": "*Dentry",
+ "Linker": "*Dentry",
+ },
+)
+
+go_template_instance(
name = "fstree",
out = "fstree.go",
package = "kernfs",
@@ -27,17 +39,6 @@ go_template_instance(
)
go_template_instance(
- name = "dentry_refs",
- out = "dentry_refs.go",
- package = "kernfs",
- prefix = "Dentry",
- template = "//pkg/refsvfs2:refs_template",
- types = {
- "T": "Dentry",
- },
-)
-
-go_template_instance(
name = "static_directory_refs",
out = "static_directory_refs.go",
package = "kernfs",
@@ -84,7 +85,7 @@ go_template_instance(
go_library(
name = "kernfs",
srcs = [
- "dentry_refs.go",
+ "dentry_list.go",
"dynamic_bytes_file.go",
"fd_impl_util.go",
"filesystem.go",
@@ -105,6 +106,7 @@ go_library(
"//pkg/log",
"//pkg/refs",
"//pkg/refsvfs2",
+ "//pkg/sentry/fs/fsutil",
"//pkg/sentry/fs/lock",
"//pkg/sentry/kernel/auth",
"//pkg/sentry/kernel/time",
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index 25184dbf9..5c5e09ac5 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -107,6 +107,17 @@ type Filesystem struct {
// nextInoMinusOne is used to to allocate inode numbers on this
// filesystem. Must be accessed by atomic operations.
nextInoMinusOne uint64
+
+ // 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 mu.
+ cachedDentries dentryList
+ cachedDentriesLen uint64
+
+ // MaxCachedDentries is the maximum size of cachedDentries. If not set,
+ // defaults to 0 and kernfs does not cache any dentries. This is immutable.
+ MaxCachedDentries uint64
}
// deferDecRef defers dropping a dentry ref until the next call to
@@ -165,7 +176,12 @@ const (
// +stateify savable
type Dentry struct {
vfsd vfs.Dentry
- DentryRefs
+
+ // refs is the reference count. When refs reaches 0, the dentry may be
+ // added to the cache or destroyed. If refs == -1, the dentry has already
+ // been destroyed. refs are allowed to go to 0 and increase again. refs is
+ // accessed using atomic memory operations.
+ refs int64
// fs is the owning filesystem. fs is immutable.
fs *Filesystem
@@ -177,6 +193,12 @@ type Dentry struct {
parent *Dentry
name string
+ // If cached is true, dentryEntry links dentry into
+ // Filesystem.cachedDentries. cached and dentryEntry are protected by
+ // Filesystem.mu.
+ cached bool
+ dentryEntry
+
// dirMu protects children and the names of child Dentries.
//
// Note that holding fs.mu for writing is not sufficient;
@@ -188,6 +210,150 @@ type Dentry struct {
inode Inode
}
+// IncRef implements vfs.DentryImpl.IncRef.
+func (d *Dentry) IncRef() {
+ // d.refs may be 0 if d.fs.mu is locked, which serializes against
+ // d.cacheLocked().
+ 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(ctx context.Context) {
+ if refs := atomic.AddInt64(&d.refs, -1); refs == 0 {
+ d.fs.mu.Lock()
+ d.cacheLocked(ctx)
+ d.fs.mu.Unlock()
+ } else if refs < 0 {
+ panic("kernfs.Dentry.DecRef() called without holding a reference")
+ }
+}
+
+// cacheLocked should be called after d's reference count becomes 0. The ref
+// count check may happen before acquiring d.fs.mu so there might be a race
+// condition where the ref count is increased again by the time the caller
+// acquires d.fs.mu. This race is handled.
+// Only reachable dentries are added to the cache. However, a dentry might
+// become unreachable *while* it is in the cache due to invalidation.
+//
+// Preconditions: d.fs.mu must be locked for writing.
+func (d *Dentry) cacheLocked(ctx context.Context) {
+ // 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 d.fs.mu, so if d.refs is zero then it will
+ // remain zero while we hold d.fs.mu for writing.)
+ refs := atomic.LoadInt64(&d.refs)
+ if refs == -1 {
+ // Dentry has already been destroyed.
+ panic(fmt.Sprintf("cacheLocked called on a dentry which has already been destroyed: %v", d))
+ }
+ if refs > 0 {
+ if d.cached {
+ d.fs.cachedDentries.Remove(d)
+ d.fs.cachedDentriesLen--
+ d.cached = false
+ }
+ return
+ }
+ // If the dentry is deleted and invalidated or has no parent, then it is no
+ // longer reachable by path resolution and should be dropped immediately
+ // because it has zero references.
+ // Note that a dentry may not always have a parent; for example magic links
+ // as described in Inode.Getlink.
+ if isDead := d.VFSDentry().IsDead(); isDead || d.parent == nil {
+ if !isDead {
+ d.fs.vfsfs.VirtualFilesystem().InvalidateDentry(ctx, d.VFSDentry())
+ }
+ if d.cached {
+ d.fs.cachedDentries.Remove(d)
+ d.fs.cachedDentriesLen--
+ d.cached = false
+ }
+ d.destroyLocked(ctx)
+ 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.MaxCachedDentries {
+ return
+ }
+ // Evict the least recently used dentry because cache size is greater than
+ // max cache size (configured on mount).
+ 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
+ // after it was inserted into fs.cachedDentries.
+ if atomic.LoadInt64(&victim.refs) == 0 {
+ if !victim.vfsd.IsDead() {
+ victim.parent.dirMu.Lock()
+ // 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(ctx, victim.VFSDentry())
+ delete(victim.parent.children, victim.name)
+ victim.parent.dirMu.Unlock()
+ }
+ victim.destroyLocked(ctx)
+ }
+ // Whether or not victim was destroyed, we brought fs.cachedDentriesLen
+ // back down to fs.MaxCachedDentries, so we don't loop.
+}
+
+// destroyLocked destroys the dentry.
+//
+// Preconditions:
+// * d.fs.mu must be locked for writing.
+// * d.refs == 0.
+// * d should have been removed from d.parent.children, i.e. d is not reachable
+// by path traversal.
+// * d.vfsd.IsDead() is true.
+func (d *Dentry) destroyLocked(ctx context.Context) {
+ 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")
+ }
+
+ d.inode.DecRef(ctx) // IncRef from Init.
+ d.inode = nil
+
+ // Drop the reference held by d on its parent without recursively locking
+ // d.fs.mu.
+ if d.parent != nil {
+ if refs := atomic.AddInt64(&d.parent.refs, -1); refs == 0 {
+ d.parent.cacheLocked(ctx)
+ } else if refs < 0 {
+ panic("kernfs.Dentry.DecRef() called without holding a reference")
+ }
+ }
+}
+
// Init initializes this dentry.
//
// Precondition: Caller must hold a reference on inode.
@@ -197,6 +363,7 @@ func (d *Dentry) Init(fs *Filesystem, inode Inode) {
d.vfsd.Init(d)
d.fs = fs
d.inode = inode
+ atomic.StoreInt64(&d.refs, 1)
ftype := inode.Mode().FileType()
if ftype == linux.ModeDirectory {
d.flags |= dflagsIsDir
@@ -204,7 +371,6 @@ func (d *Dentry) Init(fs *Filesystem, inode Inode) {
if ftype == linux.ModeSymlink {
d.flags |= dflagsIsSymlink
}
- d.EnableLeakCheck()
}
// VFSDentry returns the generic vfs dentry for this kernfs dentry.
@@ -222,32 +388,6 @@ func (d *Dentry) isSymlink() bool {
return atomic.LoadUint32(&d.flags)&dflagsIsSymlink != 0
}
-// DecRef implements vfs.DentryImpl.DecRef.
-func (d *Dentry) DecRef(ctx context.Context) {
- decRefParent := false
- d.fs.mu.Lock()
- d.DentryRefs.DecRef(func() {
- d.inode.DecRef(ctx) // IncRef from Init.
- d.inode = nil
- if d.parent != nil {
- // We will DecRef d.parent once all locks are dropped.
- decRefParent = true
- d.parent.dirMu.Lock()
- // Remove d from parent.children. It might already have been
- // removed due to invalidation.
- if _, ok := d.parent.children[d.name]; ok {
- delete(d.parent.children, d.name)
- d.fs.VFSFilesystem().VirtualFilesystem().InvalidateDentry(ctx, d.VFSDentry())
- }
- d.parent.dirMu.Unlock()
- }
- })
- d.fs.mu.Unlock()
- if decRefParent {
- d.parent.DecRef(ctx) // IncRef from Dentry.insertChild.
- }
-}
-
// InotifyWithParent implements vfs.DentryImpl.InotifyWithParent.
//
// Although Linux technically supports inotify on pseudo filesystems (inotify
diff --git a/pkg/sentry/fsimpl/proc/filesystem.go b/pkg/sentry/fsimpl/proc/filesystem.go
index ba809b92d..99abcab66 100644
--- a/pkg/sentry/fsimpl/proc/filesystem.go
+++ b/pkg/sentry/fsimpl/proc/filesystem.go
@@ -17,6 +17,7 @@ package proc
import (
"fmt"
+ "strconv"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
@@ -24,10 +25,14 @@ import (
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
+ "gvisor.dev/gvisor/pkg/syserror"
)
-// Name is the default filesystem name.
-const Name = "proc"
+const (
+ // Name is the default filesystem name.
+ Name = "proc"
+ defaultMaxCachedDentries = uint64(1000)
+)
// FilesystemType is the factory class for procfs.
//
@@ -63,9 +68,22 @@ func (ft FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualF
if err != nil {
return nil, nil, err
}
+
+ mopts := vfs.GenericParseMountOptions(opts.Data)
+ maxCachedDentries := defaultMaxCachedDentries
+ 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("proc.FilesystemType.GetFilesystem: invalid dentry cache limit: dentry_cache_limit=%s", str)
+ return nil, nil, syserror.EINVAL
+ }
+ }
+
procfs := &filesystem{
devMinor: devMinor,
}
+ procfs.MaxCachedDentries = maxCachedDentries
procfs.VFSFilesystem().Init(vfsObj, &ft, procfs)
var cgroups map[string]string
diff --git a/pkg/sentry/fsimpl/sys/sys.go b/pkg/sentry/fsimpl/sys/sys.go
index 54fa5eced..7d2147141 100644
--- a/pkg/sentry/fsimpl/sys/sys.go
+++ b/pkg/sentry/fsimpl/sys/sys.go
@@ -18,6 +18,7 @@ package sys
import (
"bytes"
"fmt"
+ "strconv"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
@@ -29,9 +30,12 @@ import (
"gvisor.dev/gvisor/pkg/syserror"
)
-// Name is the default filesystem name.
-const Name = "sysfs"
-const defaultSysDirMode = linux.FileMode(0755)
+const (
+ // Name is the default filesystem name.
+ Name = "sysfs"
+ defaultSysDirMode = linux.FileMode(0755)
+ defaultMaxCachedDentries = uint64(1000)
+)
// FilesystemType implements vfs.FilesystemType.
//
@@ -62,9 +66,21 @@ func (fsType FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
return nil, nil, err
}
+ mopts := vfs.GenericParseMountOptions(opts.Data)
+ maxCachedDentries := defaultMaxCachedDentries
+ 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("sys.FilesystemType.GetFilesystem: invalid dentry cache limit: dentry_cache_limit=%s", str)
+ return nil, nil, syserror.EINVAL
+ }
+ }
+
fs := &filesystem{
devMinor: devMinor,
}
+ fs.MaxCachedDentries = maxCachedDentries
fs.VFSFilesystem().Init(vfsObj, &fsType, fs)
root := fs.newDir(ctx, creds, defaultSysDirMode, map[string]kernfs.Inode{
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-26 09:47:39 +0000