From b44408b40e3e8762a77ccf5eeb7f2ef567235c43 Mon Sep 17 00:00:00 2001
From: Dean Deng <deandeng@google.com>
Date: Tue, 4 Aug 2020 18:18:01 -0700
Subject: Automated rollback of changelist 324906582

PiperOrigin-RevId: 324931854
---
 pkg/sentry/fsimpl/tmpfs/BUILD    | 13 -------------
 pkg/sentry/fsimpl/tmpfs/tmpfs.go | 27 +++++++++++++++++++++------
 2 files changed, 21 insertions(+), 19 deletions(-)

(limited to 'pkg/sentry')

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 {
-- 
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