Automated rollback of changelist 324906582

PiperOrigin-RevId: 324931854

6 files changed, 21 insertions, 223 deletions

diff --git a/pkg/refs/refcounter.go b/pkg/refs/refcounter.go
index 3f39edb66..61790221b 100644
--- a/pkg/refs/refcounter.go
+++ b/pkg/refs/refcounter.go
@@ -215,8 +215,6 @@ type AtomicRefCount struct {
 // LeakMode configures the leak checker.
 type LeakMode uint32
 
-// TODO(gvisor.dev/issue/1624): Simplify down to two modes once vfs1 ref
-// counting is gone.
 const (
 	// UninitializedLeakChecking indicates that the leak checker has not yet been initialized.
 	UninitializedLeakChecking LeakMode = iota
@@ -246,11 +244,6 @@ func SetLeakMode(mode LeakMode) {
 	atomic.StoreUint32(&leakMode, uint32(mode))
 }
 
-// GetLeakMode returns the current leak mode.
-func GetLeakMode() LeakMode {
-	return LeakMode(atomic.LoadUint32(&leakMode))
-}
-
 const maxStackFrames = 40
 
 type fileLine struct {
diff --git a/pkg/refs_vfs2/BUILD b/pkg/refs_vfs2/BUILD
deleted file mode 100644
index 7f180c7bd..000000000
--- a/pkg/refs_vfs2/BUILD
+++ /dev/null
@@ -1,28 +0,0 @@
-load("//tools:defs.bzl", "go_library")
-load("//tools/go_generics:defs.bzl", "go_template")
-
-package(licenses = ["notice"])
-
-go_template(
-    name = "refs_template",
-    srcs = [
-        "refs_template.go",
-    ],
-    types = [
-        "T",
-    ],
-    visibility = ["//pkg/sentry:internal"],
-    deps = [
-        "//pkg/log",
-        "//pkg/refs",
-    ],
-)
-
-go_library(
-    name = "refs",
-    srcs = [
-        "refs.go",
-    ],
-    visibility = ["//pkg/sentry:internal"],
-    deps = ["//pkg/context"],
-)
diff --git a/pkg/refs_vfs2/refs.go b/pkg/refs_vfs2/refs.go
deleted file mode 100644
index ee01b17b0..000000000
--- a/pkg/refs_vfs2/refs.go
+++ /dev/null
@@ -1,36 +0,0 @@
-// Copyright 2020 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 refs defines an interface for a reference-counted object.
-package refs
-
-import (
-	"gvisor.dev/gvisor/pkg/context"
-)
-
-// RefCounter is the interface to be implemented by objects that are reference
-// counted.
-type RefCounter interface {
-	// IncRef increments the reference counter on the object.
-	IncRef()
-
-	// DecRef decrements the object's reference count. Users of refs_template.Refs
-	// may specify a destructor to be called once the reference count reaches zero.
-	DecRef(ctx context.Context)
-
-	// TryIncRef attempts to increment the reference count, but may fail if all
-	// references have already been dropped, in which case it returns false. If
-	// true is returned, then a valid reference is now held on the object.
-	TryIncRef() bool
-}
diff --git a/pkg/refs_vfs2/refs_template.go b/pkg/refs_vfs2/refs_template.go
deleted file mode 100644
index 3e5b458c7..000000000
--- a/pkg/refs_vfs2/refs_template.go
+++ /dev/null
@@ -1,133 +0,0 @@
-// Copyright 2020 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 refs_template defines a template that can be used by reference counted
-// objects.
-package refs_template
-
-import (
-	"runtime"
-	"sync/atomic"
-
-	"gvisor.dev/gvisor/pkg/log"
-	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
-)
-
-// T is the type of the reference counted object. It is only used to customize
-// debug output when leak checking.
-type T interface{}
-
-// ownerType is used to customize logging. Note that we use a pointer to T so
-// that we do not copy the entire object when passed as a format parameter.
-var ownerType *T
-
-// Refs implements refs.RefCounter. It keeps a reference count using atomic
-// operations and calls the destructor when the count reaches zero.
-//
-// Note that the number of references is actually refCount + 1 so that a default
-// zero-value Refs object contains one reference.
-//
-// +stateify savable
-type Refs struct {
-	// refCount is composed of two fields:
-	//
-	//	[32-bit speculative references]:[32-bit real references]
-	//
-	// Speculative references are used for TryIncRef, to avoid a CompareAndSwap
-	// loop. See IncRef, DecRef and TryIncRef for details of how these fields are
-	// used.
-	refCount int64
-}
-
-func (r *Refs) finalize() {
-	var note string
-	switch refs_vfs1.GetLeakMode() {
-	case refs_vfs1.NoLeakChecking:
-		return
-	case refs_vfs1.UninitializedLeakChecking:
-		note = "(Leak checker uninitialized): "
-	}
-	if n := r.ReadRefs(); n != 0 {
-		log.Warningf("%sAtomicRefCount %p owned by %T garbage collected with ref count of %d (want 0)", note, r, ownerType, n)
-	}
-}
-
-// EnableLeakCheck checks for reference leaks when Refs gets garbage collected.
-func (r *Refs) EnableLeakCheck() {
-	if refs_vfs1.GetLeakMode() != refs_vfs1.NoLeakChecking {
-		runtime.SetFinalizer(r, (*Refs).finalize)
-	}
-}
-
-// ReadRefs returns the current number of references. The returned count is
-// inherently racy and is unsafe to use without external synchronization.
-func (r *Refs) ReadRefs() int64 {
-	// Account for the internal -1 offset on refcounts.
-	return atomic.LoadInt64(&r.refCount) + 1
-}
-
-// IncRef implements refs.RefCounter.IncRef.
-//
-//go:nosplit
-func (r *Refs) IncRef() {
-	if v := atomic.AddInt64(&r.refCount, 1); v <= 0 {
-		panic("Incrementing non-positive ref count")
-	}
-}
-
-// TryIncRef implements refs.RefCounter.TryIncRef.
-//
-// To do this safely without a loop, a speculative reference is first acquired
-// on the object. This allows multiple concurrent TryIncRef calls to distinguish
-// other TryIncRef calls from genuine references held.
-//
-//go:nosplit
-func (r *Refs) TryIncRef() bool {
-	const speculativeRef = 1 << 32
-	v := atomic.AddInt64(&r.refCount, speculativeRef)
-	if int32(v) < 0 {
-		// This object has already been freed.
-		atomic.AddInt64(&r.refCount, -speculativeRef)
-		return false
-	}
-
-	// Turn into a real reference.
-	atomic.AddInt64(&r.refCount, -speculativeRef+1)
-	return true
-}
-
-// DecRef implements refs.RefCounter.DecRef.
-//
-// Note that speculative references are counted here. Since they were added
-// prior to real references reaching zero, they will successfully convert to
-// real references. In other words, we see speculative references only in the
-// following case:
-//
-//	A: TryIncRef [speculative increase => sees non-negative references]
-//	B: DecRef [real decrease]
-//	A: TryIncRef [transform speculative to real]
-//
-//go:nosplit
-func (r *Refs) DecRef(destroy func()) {
-	switch v := atomic.AddInt64(&r.refCount, -1); {
-	case v < -1:
-		panic("Decrementing non-positive ref count")
-
-	case v == -1:
-		// Call the destructor.
-		if destroy != nil {
-			destroy()
-		}
-	}
-}
diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 5cd428d64..e73732a6b 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -26,17 +26,6 @@ go_template_instance(
     },
 )
 
-go_template_instance(
-    name = "inode_refs",
-    out = "inode_refs.go",
-    package = "tmpfs",
-    prefix = "inode",
-    template = "//pkg/refs_vfs2:refs_template",
-    types = {
-        "T": "inode",
-    },
-)
-
 go_library(
     name = "tmpfs",
     srcs = [
@@ -45,7 +34,6 @@ go_library(
         "directory.go",
         "filesystem.go",
         "fstree.go",
-        "inode_refs.go",
         "named_pipe.go",
         "regular_file.go",
         "socket_file.go",
@@ -59,7 +47,6 @@ go_library(
         "//pkg/context",
         "//pkg/fspath",
         "//pkg/log",
-        "//pkg/refs",
         "//pkg/safemem",
         "//pkg/sentry/arch",
         "//pkg/sentry/fs",
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 5640380dc..68e615e8b 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -285,10 +285,13 @@ type inode struct {
 	// fs is the owning filesystem. fs is immutable.
 	fs *filesystem
 
+	// refs is a reference count. refs is accessed using atomic memory
+	// operations.
+	//
 	// A reference is held on all inodes as long as they are reachable in the
 	// filesystem tree, i.e. nlink is nonzero. This reference is dropped when
 	// nlink reaches 0.
-	refs inodeRefs
+	refs int64
 
 	// xattrs implements extended attributes.
 	//
@@ -324,6 +327,7 @@ func (i *inode) init(impl interface{}, fs *filesystem, kuid auth.KUID, kgid auth
 		panic("file type is required in FileMode")
 	}
 	i.fs = fs
+	i.refs = 1
 	i.mode = uint32(mode)
 	i.uid = uint32(kuid)
 	i.gid = uint32(kgid)
@@ -335,7 +339,6 @@ func (i *inode) init(impl interface{}, fs *filesystem, kuid auth.KUID, kgid auth
 	i.mtime = now
 	// i.nlink initialized by caller
 	i.impl = impl
-	i.refs.EnableLeakCheck()
 }
 
 // incLinksLocked increments i's link count.
@@ -366,15 +369,25 @@ func (i *inode) decLinksLocked(ctx context.Context) {
 }
 
 func (i *inode) incRef() {
-	i.refs.IncRef()
+	if atomic.AddInt64(&i.refs, 1) <= 1 {
+		panic("tmpfs.inode.incRef() called without holding a reference")
+	}
 }
 
 func (i *inode) tryIncRef() bool {
-	return i.refs.TryIncRef()
+	for {
+		refs := atomic.LoadInt64(&i.refs)
+		if refs == 0 {
+			return false
+		}
+		if atomic.CompareAndSwapInt64(&i.refs, refs, refs+1) {
+			return true
+		}
+	}
 }
 
 func (i *inode) decRef(ctx context.Context) {
-	i.refs.DecRef(func() {
+	if refs := atomic.AddInt64(&i.refs, -1); refs == 0 {
 		i.watches.HandleDeletion(ctx)
 		if regFile, ok := i.impl.(*regularFile); ok {
 			// Release memory used by regFile to store data. Since regFile is
@@ -382,7 +395,9 @@ func (i *inode) decRef(ctx context.Context) {
 			// metadata.
 			regFile.data.DropAll(regFile.memFile)
 		}
-	})
+	} else if refs < 0 {
+		panic("tmpfs.inode.decRef() called without holding a reference")
+	}
 }
 
 func (i *inode) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes) error {