1 files changed, 35 insertions, 7 deletions
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go
index 1f6f56293..908c69f91 100644
--- a/pkg/sentry/vfs/vfs.go
+++ b/pkg/sentry/vfs/vfs.go
@@ -16,23 +16,27 @@
 //
 // Lock order:
 //
-// FilesystemImpl/FileDescriptionImpl locks
-//   VirtualFilesystem.mountMu
-//     Dentry.mu
-//       Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry
-//     VirtualFilesystem.filesystemsMu
+// EpollInstance.interestMu
+//   FileDescription.epollMu
+//     FilesystemImpl/FileDescriptionImpl locks
+//       VirtualFilesystem.mountMu
+//         Dentry.mu
+//           Locks acquired by FilesystemImpls between Prepare{Delete,Rename}Dentry and Commit{Delete,Rename*}Dentry
+//         VirtualFilesystem.filesystemsMu
+//       EpollInstance.mu
 // VirtualFilesystem.fsTypesMu
 //
 // Locking Dentry.mu in multiple Dentries requires holding
-// VirtualFilesystem.mountMu.
+// VirtualFilesystem.mountMu. Locking EpollInstance.interestMu in multiple
+// EpollInstances requires holding epollCycleMu.
 package vfs
 
 import (
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
-	"gvisor.dev/gvisor/pkg/sentry/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -75,6 +79,14 @@ type VirtualFilesystem struct {
 	// mountpoints is analogous to Linux's mountpoint_hashtable.
 	mountpoints map[*Dentry]map[*Mount]struct{}
 
+	// anonMount is a Mount, not included in mounts or mountpoints,
+	// representing an anonFilesystem. anonMount is used to back
+	// VirtualDentries returned by VirtualFilesystem.NewAnonVirtualDentry().
+	// anonMount is immutable.
+	//
+	// anonMount is analogous to Linux's anon_inode_mnt.
+	anonMount *Mount
+
 	// devices contains all registered Devices. devices is protected by
 	// devicesMu.
 	devicesMu sync.RWMutex
@@ -110,6 +122,22 @@ func New() *VirtualFilesystem {
 		filesystems:           make(map[*Filesystem]struct{}),
 	}
 	vfs.mounts.Init()
+
+	// Construct vfs.anonMount.
+	anonfsDevMinor, err := vfs.GetAnonBlockDevMinor()
+	if err != nil {
+		panic(fmt.Sprintf("VirtualFilesystem.GetAnonBlockDevMinor() failed during VirtualFilesystem construction: %v", err))
+	}
+	anonfs := anonFilesystem{
+		devMinor: anonfsDevMinor,
+	}
+	anonfs.vfsfs.Init(vfs, &anonfs)
+	vfs.anonMount = &Mount{
+		vfs:  vfs,
+		fs:   &anonfs.vfsfs,
+		refs: 1,
+	}
+
 	return vfs
 }