Merge release-20200907.0-37-g3ca73841d (automated)

40 files changed, 750 insertions, 2042 deletions

diff --git a/pkg/sentry/fsimpl/devpts/master.go b/pkg/sentry/fsimpl/devpts/master.go
index d07e1ded8..83d790b38 100644
--- a/pkg/sentry/fsimpl/devpts/master.go
+++ b/pkg/sentry/fsimpl/devpts/master.go
@@ -17,6 +17,7 @@ package devpts
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
@@ -27,7 +28,6 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
-	"gvisor.dev/gvisor/tools/go_marshal/primitive"
 )
 
 // masterInode is the inode for the master end of the Terminal.
diff --git a/pkg/sentry/fsimpl/devpts/queue.go b/pkg/sentry/fsimpl/devpts/queue.go
index ca36b66e9..55bff3e60 100644
--- a/pkg/sentry/fsimpl/devpts/queue.go
+++ b/pkg/sentry/fsimpl/devpts/queue.go
@@ -17,6 +17,7 @@ package devpts
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
@@ -24,7 +25,6 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
-	"gvisor.dev/gvisor/tools/go_marshal/primitive"
 )
 
 // waitBufMaxBytes is the maximum size of a wait buffer. It is based on
diff --git a/pkg/sentry/fsimpl/devpts/replica.go b/pkg/sentry/fsimpl/devpts/replica.go
index 1f99f4b4d..58f6c1d3a 100644
--- a/pkg/sentry/fsimpl/devpts/replica.go
+++ b/pkg/sentry/fsimpl/devpts/replica.go
@@ -17,6 +17,7 @@ package devpts
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
@@ -26,7 +27,6 @@ import (
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 	"gvisor.dev/gvisor/pkg/waiter"
-	"gvisor.dev/gvisor/tools/go_marshal/primitive"
 )
 
 // replicaInode is the inode for the replica end of the Terminal.
diff --git a/pkg/sentry/fsimpl/devpts/root_inode_refs.go b/pkg/sentry/fsimpl/devpts/root_inode_refs.go
index 068ee2f20..051801202 100644
--- a/pkg/sentry/fsimpl/devpts/root_inode_refs.go
+++ b/pkg/sentry/fsimpl/devpts/root_inode_refs.go
@@ -1,10 +1,10 @@
 package devpts
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/devpts/terminal.go b/pkg/sentry/fsimpl/devpts/terminal.go
index 731955d62..510bd6d89 100644
--- a/pkg/sentry/fsimpl/devpts/terminal.go
+++ b/pkg/sentry/fsimpl/devpts/terminal.go
@@ -17,9 +17,9 @@ package devpts
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/tools/go_marshal/primitive"
 )
 
 // Terminal is a pseudoterminal.
diff --git a/pkg/sentry/fsimpl/fuse/connection.go b/pkg/sentry/fsimpl/fuse/connection.go
index a7402c149..eb1d1a2b7 100644
--- a/pkg/sentry/fsimpl/fuse/connection.go
+++ b/pkg/sentry/fsimpl/fuse/connection.go
@@ -15,17 +15,31 @@
 package fuse
 
 import (
+	"errors"
+	"fmt"
 	"sync"
+	"sync/atomic"
+	"syscall"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/marshal"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
+// maxActiveRequestsDefault is the default setting controlling the upper bound
+// on the number of active requests at any given time.
+const maxActiveRequestsDefault = 10000
+
+// Ordinary requests have even IDs, while interrupts IDs are odd.
+// Used to increment the unique ID for each FUSE request.
+var reqIDStep uint64 = 2
+
 const (
 	// fuseDefaultMaxBackground is the default value for MaxBackground.
 	fuseDefaultMaxBackground = 12
@@ -38,36 +52,43 @@ const (
 	fuseDefaultMaxPagesPerReq = 32
 )
 
+// Request represents a FUSE operation request that hasn't been sent to the
+// server yet.
+//
+// +stateify savable
+type Request struct {
+	requestEntry
+
+	id   linux.FUSEOpID
+	hdr  *linux.FUSEHeaderIn
+	data []byte
+}
+
+// Response represents an actual response from the server, including the
+// response payload.
+//
+// +stateify savable
+type Response struct {
+	opcode linux.FUSEOpcode
+	hdr    linux.FUSEHeaderOut
+	data   []byte
+}
+
 // connection is the struct by which the sentry communicates with the FUSE server daemon.
-// Lock order:
-// - conn.fd.mu
-// - conn.mu
-// - conn.asyncMu
 type connection struct {
 	fd *DeviceFD
 
-	// mu protects access to struct memebers.
-	mu sync.Mutex
-
-	// attributeVersion is the version of connection's attributes.
-	attributeVersion uint64
-
-	// We target FUSE 7.23.
 	// The following FUSE_INIT flags are currently unsupported by this implementation:
+	// - FUSE_ATOMIC_O_TRUNC: requires open(..., O_TRUNC)
 	// - FUSE_EXPORT_SUPPORT
+	// - FUSE_HANDLE_KILLPRIV
 	// - FUSE_POSIX_LOCKS: requires POSIX locks
 	// - FUSE_FLOCK_LOCKS: requires POSIX locks
 	// - FUSE_AUTO_INVAL_DATA: requires page caching eviction
+	// - FUSE_EXPLICIT_INVAL_DATA: requires page caching eviction
 	// - FUSE_DO_READDIRPLUS/FUSE_READDIRPLUS_AUTO: requires FUSE_READDIRPLUS implementation
 	// - FUSE_ASYNC_DIO
-	// - FUSE_PARALLEL_DIROPS (7.25)
-	// - FUSE_HANDLE_KILLPRIV (7.26)
-	// - FUSE_POSIX_ACL: affects defaultPermissions, posixACL, xattr handler (7.26)
-	// - FUSE_ABORT_ERROR (7.27)
-	// - FUSE_CACHE_SYMLINKS (7.28)
-	// - FUSE_NO_OPENDIR_SUPPORT (7.29)
-	// - FUSE_EXPLICIT_INVAL_DATA: requires page caching eviction (7.30)
-	// - FUSE_MAP_ALIGNMENT (7.31)
+	// - FUSE_POSIX_ACL: affects defaultPermissions, posixACL, xattr handler
 
 	// initialized after receiving FUSE_INIT reply.
 	// Until it's set, suspend sending FUSE requests.
@@ -77,6 +98,10 @@ type connection struct {
 	// initializedChan is used to block requests before initialization.
 	initializedChan chan struct{}
 
+	// blocked when there are too many outstading backgrounds requests (NumBackground == MaxBackground).
+	// TODO(gvisor.dev/issue/3185): update the numBackground accordingly; use a channel to block.
+	blocked bool
+
 	// connected (connection established) when a new FUSE file system is created.
 	// Set to false when:
 	//   umount,
@@ -84,55 +109,48 @@ type connection struct {
 	//   device release.
 	connected bool
 
+	// aborted via sysfs.
+	// TODO(gvisor.dev/issue/3185): abort all queued requests.
+	aborted bool
+
 	// connInitError if FUSE_INIT encountered error (major version mismatch).
 	// Only set in INIT.
 	connInitError bool
 
 	// connInitSuccess if FUSE_INIT is successful.
 	// Only set in INIT.
-	// Used for destory (not yet implemented).
+	// Used for destory.
 	connInitSuccess bool
 
-	// aborted via sysfs, and will send ECONNABORTED to read after disconnection (instead of ENODEV).
-	// Set only if abortErr is true and via fuse control fs (not yet implemented).
-	// TODO(gvisor.dev/issue/3525): set this to true when user aborts.
-	aborted bool
+	// TODO(gvisor.dev/issue/3185): All the queue logic are working in progress.
 
-	// numWating is the number of requests waiting to be
-	// sent to FUSE device or being processed by FUSE daemon.
-	numWaiting uint32
+	// NumberBackground is the number of requests in the background.
+	numBackground uint16
 
-	// Terminology note:
-	//
-	// - `asyncNumMax` is the `MaxBackground` in the FUSE_INIT_IN struct.
-	//
-	// - `asyncCongestionThreshold` is the `CongestionThreshold` in the FUSE_INIT_IN struct.
-	//
-	// We call the "background" requests in unix term as async requests.
-	// The "async requests" in unix term is our async requests that expect a reply,
-	// i.e. `!requestOptions.noReply`
+	// congestionThreshold for NumBackground.
+	// Negotiated in FUSE_INIT.
+	congestionThreshold uint16
+
+	// maxBackground is the maximum number of NumBackground.
+	// Block connection when it is reached.
+	// Negotiated in FUSE_INIT.
+	maxBackground uint16
 
-	// asyncMu protects the async request fields.
-	asyncMu sync.Mutex
+	// numActiveBackground is the number of requests in background and has being marked as active.
+	numActiveBackground uint16
 
-	// asyncNum is the number of async requests.
-	// Protected by asyncMu.
-	asyncNum uint16
+	// numWating is the number of requests waiting for completion.
+	numWaiting uint32
 
-	// asyncCongestionThreshold the number of async requests.
-	// Negotiated in FUSE_INIT as "CongestionThreshold".
-	// TODO(gvisor.dev/issue/3529): add congestion control.
-	// Protected by asyncMu.
-	asyncCongestionThreshold uint16
+	// TODO(gvisor.dev/issue/3185): BgQueue
+	// some queue for background queued requests.
 
-	// asyncNumMax is the maximum number of asyncNum.
-	// Connection blocks the async requests when it is reached.
-	// Negotiated in FUSE_INIT as "MaxBackground".
-	// Protected by asyncMu.
-	asyncNumMax uint16
+	// bgLock protects:
+	// MaxBackground, CongestionThreshold, NumBackground,
+	// NumActiveBackground, BgQueue, Blocked.
+	bgLock sync.Mutex
 
 	// maxRead is the maximum size of a read buffer in in bytes.
-	// Initialized from a fuse fs parameter.
 	maxRead uint32
 
 	// maxWrite is the maximum size of a write buffer in bytes.
@@ -147,20 +165,23 @@ type connection struct {
 	// Negotiated and only set in INIT.
 	minor uint32
 
-	// atomicOTrunc is true when FUSE does not send a separate SETATTR request
-	// before open with O_TRUNC flag.
-	// Negotiated and only set in INIT.
-	atomicOTrunc bool
-
 	// asyncRead if read pages asynchronously.
 	// Negotiated and only set in INIT.
 	asyncRead bool
 
+	// abortErr is true if kernel need to return an unique read error after abort.
+	// Negotiated and only set in INIT.
+	abortErr bool
+
 	// writebackCache is true for write-back cache policy,
 	// false for write-through policy.
 	// Negotiated and only set in INIT.
 	writebackCache bool
 
+	// cacheSymlinks if filesystem needs to cache READLINK responses in page cache.
+	// Negotiated and only set in INIT.
+	cacheSymlinks bool
+
 	// bigWrites if doing multi-page cached writes.
 	// Negotiated and only set in INIT.
 	bigWrites bool
@@ -168,70 +189,116 @@ type connection struct {
 	// dontMask if filestestem does not apply umask to creation modes.
 	// Negotiated in INIT.
 	dontMask bool
-
-	// noOpen if FUSE server doesn't support open operation.
-	// This flag only influence performance, not correctness of the program.
-	noOpen bool
 }
 
 // newFUSEConnection creates a FUSE connection to fd.
-func newFUSEConnection(_ context.Context, fd *vfs.FileDescription, opts *filesystemOptions) (*connection, error) {
+func newFUSEConnection(_ context.Context, fd *vfs.FileDescription, maxInFlightRequests uint64) (*connection, error) {
 	// Mark the device as ready so it can be used. /dev/fuse can only be used if the FD was used to
 	// mount a FUSE filesystem.
 	fuseFD := fd.Impl().(*DeviceFD)
+	fuseFD.mounted = true
 
 	// Create the writeBuf for the header to be stored in.
 	hdrLen := uint32((*linux.FUSEHeaderOut)(nil).SizeBytes())
 	fuseFD.writeBuf = make([]byte, hdrLen)
 	fuseFD.completions = make(map[linux.FUSEOpID]*futureResponse)
-	fuseFD.fullQueueCh = make(chan struct{}, opts.maxActiveRequests)
+	fuseFD.fullQueueCh = make(chan struct{}, maxInFlightRequests)
 	fuseFD.writeCursor = 0
 
 	return &connection{
-		fd:                       fuseFD,
-		asyncNumMax:              fuseDefaultMaxBackground,
-		asyncCongestionThreshold: fuseDefaultCongestionThreshold,
-		maxRead:                  opts.maxRead,
-		maxPages:                 fuseDefaultMaxPagesPerReq,
-		initializedChan:          make(chan struct{}),
-		connected:                true,
+		fd:                  fuseFD,
+		maxBackground:       fuseDefaultMaxBackground,
+		congestionThreshold: fuseDefaultCongestionThreshold,
+		maxPages:            fuseDefaultMaxPagesPerReq,
+		initializedChan:     make(chan struct{}),
+		connected:           true,
 	}, nil
 }
 
-// CallAsync makes an async (aka background) request.
-// It's a simple wrapper around Call().
-func (conn *connection) CallAsync(t *kernel.Task, r *Request) error {
-	r.async = true
-	_, err := conn.Call(t, r)
-	return err
+// SetInitialized atomically sets the connection as initialized.
+func (conn *connection) SetInitialized() {
+	// Unblock the requests sent before INIT.
+	close(conn.initializedChan)
+
+	// Close the channel first to avoid the non-atomic situation
+	// where conn.initialized is true but there are
+	// tasks being blocked on the channel.
+	// And it prevents the newer tasks from gaining
+	// unnecessary higher chance to be issued before the blocked one.
+
+	atomic.StoreInt32(&(conn.initialized), int32(1))
 }
 
-// Call makes a request to the server.
-// Block before the connection is initialized.
-// When the Request is FUSE_INIT, it will not be blocked before initialization.
-// Task should never be nil.
-//
-// For a sync request, it blocks the invoking task until
-// a server responds with a response.
-//
-// For an async request (that do not expect a response immediately),
-// it returns directly unless being blocked either before initialization
-// or when there are too many async requests ongoing.
-//
-// Example for async request:
-// init, readahead, write, async read/write, fuse_notify_reply,
-// non-sync release, interrupt, forget.
-//
-// The forget request does not have a reply,
-// as documented in include/uapi/linux/fuse.h:FUSE_FORGET.
+// IsInitialized atomically check if the connection is initialized.
+// pairs with SetInitialized().
+func (conn *connection) Initialized() bool {
+	return atomic.LoadInt32(&(conn.initialized)) != 0
+}
+
+// NewRequest creates a new request that can be sent to the FUSE server.
+func (conn *connection) NewRequest(creds *auth.Credentials, pid uint32, ino uint64, opcode linux.FUSEOpcode, payload marshal.Marshallable) (*Request, error) {
+	conn.fd.mu.Lock()
+	defer conn.fd.mu.Unlock()
+	conn.fd.nextOpID += linux.FUSEOpID(reqIDStep)
+
+	hdrLen := (*linux.FUSEHeaderIn)(nil).SizeBytes()
+	hdr := linux.FUSEHeaderIn{
+		Len:    uint32(hdrLen + payload.SizeBytes()),
+		Opcode: opcode,
+		Unique: conn.fd.nextOpID,
+		NodeID: ino,
+		UID:    uint32(creds.EffectiveKUID),
+		GID:    uint32(creds.EffectiveKGID),
+		PID:    pid,
+	}
+
+	buf := make([]byte, hdr.Len)
+	hdr.MarshalUnsafe(buf[:hdrLen])
+	payload.MarshalUnsafe(buf[hdrLen:])
+
+	return &Request{
+		id:   hdr.Unique,
+		hdr:  &hdr,
+		data: buf,
+	}, nil
+}
+
+// Call makes a request to the server and blocks the invoking task until a
+// server responds with a response. Task should never be nil.
+// Requests will not be sent before the connection is initialized.
+// For async tasks, use CallAsync().
 func (conn *connection) Call(t *kernel.Task, r *Request) (*Response, error) {
 	// Block requests sent before connection is initalized.
-	if !conn.Initialized() && r.hdr.Opcode != linux.FUSE_INIT {
+	if !conn.Initialized() {
 		if err := t.Block(conn.initializedChan); err != nil {
 			return nil, err
 		}
 	}
 
+	return conn.call(t, r)
+}
+
+// CallAsync makes an async (aka background) request.
+// Those requests either do not expect a response (e.g. release) or
+// the response should be handled by others (e.g. init).
+// Return immediately unless the connection is blocked (before initialization).
+// Async call example: init, release, forget, aio, interrupt.
+// When the Request is FUSE_INIT, it will not be blocked before initialization.
+func (conn *connection) CallAsync(t *kernel.Task, r *Request) error {
+	// Block requests sent before connection is initalized.
+	if !conn.Initialized() && r.hdr.Opcode != linux.FUSE_INIT {
+		if err := t.Block(conn.initializedChan); err != nil {
+			return err
+		}
+	}
+
+	// This should be the only place that invokes call() with a nil task.
+	_, err := conn.call(nil, r)
+	return err
+}
+
+// call makes a call without blocking checks.
+func (conn *connection) call(t *kernel.Task, r *Request) (*Response, error) {
 	if !conn.connected {
 		return nil, syserror.ENOTCONN
 	}
@@ -248,6 +315,31 @@ func (conn *connection) Call(t *kernel.Task, r *Request) (*Response, error) {
 	return fut.resolve(t)
 }
 
+// Error returns the error of the FUSE call.
+func (r *Response) Error() error {
+	errno := r.hdr.Error
+	if errno >= 0 {
+		return nil
+	}
+
+	sysErrNo := syscall.Errno(-errno)
+	return error(sysErrNo)
+}
+
+// UnmarshalPayload unmarshals the response data into m.
+func (r *Response) UnmarshalPayload(m marshal.Marshallable) error {
+	hdrLen := r.hdr.SizeBytes()
+	haveDataLen := r.hdr.Len - uint32(hdrLen)
+	wantDataLen := uint32(m.SizeBytes())
+
+	if haveDataLen < wantDataLen {
+		return fmt.Errorf("payload too small. Minimum data lenth required: %d,  but got data length %d", wantDataLen, haveDataLen)
+	}
+
+	m.UnmarshalUnsafe(r.data[hdrLen:])
+	return nil
+}
+
 // callFuture makes a request to the server and returns a future response.
 // Call resolve() when the response needs to be fulfilled.
 func (conn *connection) callFuture(t *kernel.Task, r *Request) (*futureResponse, error) {
@@ -266,6 +358,11 @@ func (conn *connection) callFuture(t *kernel.Task, r *Request) (*futureResponse,
 	// if there are always too many ongoing requests all the time. The
 	// supported maxActiveRequests setting should be really high to avoid this.
 	for conn.fd.numActiveRequests == conn.fd.fs.opts.maxActiveRequests {
+		if t == nil {
+			// Since there is no task that is waiting. We must error out.
+			return nil, errors.New("FUSE request queue full")
+		}
+
 		log.Infof("Blocking request %v from being queued. Too many active requests: %v",
 			r.id, conn.fd.numActiveRequests)
 		conn.fd.mu.Unlock()
@@ -281,19 +378,9 @@ func (conn *connection) callFuture(t *kernel.Task, r *Request) (*futureResponse,
 
 // callFutureLocked makes a request to the server and returns a future response.
 func (conn *connection) callFutureLocked(t *kernel.Task, r *Request) (*futureResponse, error) {
-	// Check connected again holding conn.mu.
-	conn.mu.Lock()
-	if !conn.connected {
-		conn.mu.Unlock()
-		// we checked connected before,
-		// this must be due to aborted connection.
-		return nil, syserror.ECONNABORTED
-	}
-	conn.mu.Unlock()
-
 	conn.fd.queue.PushBack(r)
-	conn.fd.numActiveRequests++
-	fut := newFutureResponse(r)
+	conn.fd.numActiveRequests += 1
+	fut := newFutureResponse(r.hdr.Opcode)
 	conn.fd.completions[r.id] = fut
 
 	// Signal the readers that there is something to read.
@@ -301,3 +388,50 @@ func (conn *connection) callFutureLocked(t *kernel.Task, r *Request) (*futureRes
 
 	return fut, nil
 }
+
+// futureResponse represents an in-flight request, that may or may not have
+// completed yet. Convert it to a resolved Response by calling Resolve, but note
+// that this may block.
+//
+// +stateify savable
+type futureResponse struct {
+	opcode linux.FUSEOpcode
+	ch     chan struct{}
+	hdr    *linux.FUSEHeaderOut
+	data   []byte
+}
+
+// newFutureResponse creates a future response to a FUSE request.
+func newFutureResponse(opcode linux.FUSEOpcode) *futureResponse {
+	return &futureResponse{
+		opcode: opcode,
+		ch:     make(chan struct{}),
+	}
+}
+
+// resolve blocks the task until the server responds to its corresponding request,
+// then returns a resolved response.
+func (f *futureResponse) resolve(t *kernel.Task) (*Response, error) {
+	// If there is no Task associated with this request  - then we don't try to resolve
+	// the response.  Instead, the task writing the response (proxy to the server) will
+	// process the response on our behalf.
+	if t == nil {
+		log.Infof("fuse.Response.resolve: Not waiting on a response from server.")
+		return nil, nil
+	}
+
+	if err := t.Block(f.ch); err != nil {
+		return nil, err
+	}
+
+	return f.getResponse(), nil
+}
+
+// getResponse creates a Response from the data the futureResponse has.
+func (f *futureResponse) getResponse() *Response {
+	return &Response{
+		opcode: f.opcode,
+		hdr:    *f.hdr,
+		data:   f.data,
+	}
+}
diff --git a/pkg/sentry/fsimpl/fuse/dev.go b/pkg/sentry/fsimpl/fuse/dev.go
index 64c3e32e2..e522ff9a0 100644
--- a/pkg/sentry/fsimpl/fuse/dev.go
+++ b/pkg/sentry/fsimpl/fuse/dev.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
@@ -55,6 +56,9 @@ type DeviceFD struct {
 	vfs.DentryMetadataFileDescriptionImpl
 	vfs.NoLockFD
 
+	// mounted specifies whether a FUSE filesystem was mounted using the DeviceFD.
+	mounted bool
+
 	// nextOpID is used to create new requests.
 	nextOpID linux.FUSEOpID
 
@@ -96,15 +100,13 @@ type DeviceFD struct {
 
 // Release implements vfs.FileDescriptionImpl.Release.
 func (fd *DeviceFD) Release(context.Context) {
-	if fd.fs != nil {
-		fd.fs.conn.connected = false
-	}
+	fd.fs.conn.connected = false
 }
 
 // PRead implements vfs.FileDescriptionImpl.PRead.
 func (fd *DeviceFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
 	// Operations on /dev/fuse don't make sense until a FUSE filesystem is mounted.
-	if fd.fs == nil {
+	if !fd.mounted {
 		return 0, syserror.EPERM
 	}
 
@@ -114,16 +116,10 @@ func (fd *DeviceFD) PRead(ctx context.Context, dst usermem.IOSequence, offset in
 // Read implements vfs.FileDescriptionImpl.Read.
 func (fd *DeviceFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
 	// Operations on /dev/fuse don't make sense until a FUSE filesystem is mounted.
-	if fd.fs == nil {
+	if !fd.mounted {
 		return 0, syserror.EPERM
 	}
 
-	// Return ENODEV if the filesystem is umounted.
-	if fd.fs.umounted {
-		// TODO(gvisor.dev/issue/3525): return ECONNABORTED if aborted via fuse control fs.
-		return 0, syserror.ENODEV
-	}
-
 	// We require that any Read done on this filesystem have a sane minimum
 	// read buffer. It must have the capacity for the fixed parts of any request
 	// header (Linux uses the request header and the FUSEWriteIn header for this
@@ -147,82 +143,58 @@ func (fd *DeviceFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.R
 }
 
 // readLocked implements the reading of the fuse device while locked with DeviceFD.mu.
-//
-// Preconditions: dst is large enough for any reasonable request.
 func (fd *DeviceFD) readLocked(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
-	var req *Request
+	if fd.queue.Empty() {
+		return 0, syserror.ErrWouldBlock
+	}
 
-	// Find the first valid request.
-	// For the normal case this loop only execute once.
-	for !fd.queue.Empty() {
-		req = fd.queue.Front()
+	var readCursor uint32
+	var bytesRead int64
+	for {
+		req := fd.queue.Front()
+		if dst.NumBytes() < int64(req.hdr.Len) {
+			// The request is too large. Cannot process it. All requests must be smaller than the
+			// negotiated size as specified by Connection.MaxWrite set as part of the FUSE_INIT
+			// handshake.
+			errno := -int32(syscall.EIO)
+			if req.hdr.Opcode == linux.FUSE_SETXATTR {
+				errno = -int32(syscall.E2BIG)
+			}
 
-		if int64(req.hdr.Len)+int64(len(req.payload)) <= dst.NumBytes() {
-			break
-		}
+			// Return the error to the calling task.
+			if err := fd.sendError(ctx, errno, req); err != nil {
+				return 0, err
+			}
 
-		// The request is too large. Cannot process it. All requests must be smaller than the
-		// negotiated size as specified by Connection.MaxWrite set as part of the FUSE_INIT
-		// handshake.
-		errno := -int32(syscall.EIO)
-		if req.hdr.Opcode == linux.FUSE_SETXATTR {
-			errno = -int32(syscall.E2BIG)
-		}
+			// We're done with this request.
+			fd.queue.Remove(req)
 
-		// Return the error to the calling task.
-		if err := fd.sendError(ctx, errno, req.hdr.Unique); err != nil {
-			return 0, err
+			// Restart the read as this request was invalid.
+			log.Warningf("fuse.DeviceFD.Read: request found was too large. Restarting read.")
+			return fd.readLocked(ctx, dst, opts)
 		}
 
-		// We're done with this request.
-		fd.queue.Remove(req)
-		req = nil
-	}
-
-	if req == nil {
-		return 0, syserror.ErrWouldBlock
-	}
-
-	// We already checked the size: dst must be able to fit the whole request.
-	// Now we write the marshalled header, the payload,
-	// and the potential additional payload
-	// to the user memory IOSequence.
-
-	n, err := dst.CopyOut(ctx, req.data)
-	if err != nil {
-		return 0, err
-	}
-	if n != len(req.data) {
-		return 0, syserror.EIO
-	}
-
-	if req.hdr.Opcode == linux.FUSE_WRITE {
-		written, err := dst.DropFirst(n).CopyOut(ctx, req.payload)
+		n, err := dst.CopyOut(ctx, req.data[readCursor:])
 		if err != nil {
 			return 0, err
 		}
-		if written != len(req.payload) {
-			return 0, syserror.EIO
-		}
-		n += int(written)
-	}
+		readCursor += uint32(n)
+		bytesRead += int64(n)
 
-	// Fully done with this req, remove it from the queue.
-	fd.queue.Remove(req)
-
-	// Remove noReply ones from map of requests expecting a reply.
-	if req.noReply {
-		fd.numActiveRequests -= 1
-		delete(fd.completions, req.hdr.Unique)
+		if readCursor >= req.hdr.Len {
+			// Fully done with this req, remove it from the queue.
+			fd.queue.Remove(req)
+			break
+		}
 	}
 
-	return int64(n), nil
+	return bytesRead, nil
 }
 
 // PWrite implements vfs.FileDescriptionImpl.PWrite.
 func (fd *DeviceFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
 	// Operations on /dev/fuse don't make sense until a FUSE filesystem is mounted.
-	if fd.fs == nil {
+	if !fd.mounted {
 		return 0, syserror.EPERM
 	}
 
@@ -239,15 +211,10 @@ func (fd *DeviceFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.
 // writeLocked implements writing to the fuse device while locked with DeviceFD.mu.
 func (fd *DeviceFD) writeLocked(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
 	// Operations on /dev/fuse don't make sense until a FUSE filesystem is mounted.
-	if fd.fs == nil {
+	if !fd.mounted {
 		return 0, syserror.EPERM
 	}
 
-	// Return ENODEV if the filesystem is umounted.
-	if fd.fs.umounted {
-		return 0, syserror.ENODEV
-	}
-
 	var cn, n int64
 	hdrLen := uint32((*linux.FUSEHeaderOut)(nil).SizeBytes())
 
@@ -309,12 +276,7 @@ func (fd *DeviceFD) writeLocked(ctx context.Context, src usermem.IOSequence, opt
 
 			fut, ok := fd.completions[hdr.Unique]
 			if !ok {
-				if fut.hdr.Unique == linux.FUSE_RELEASE {
-					// Currently we simply discard the reply for FUSE_RELEASE.
-					return n + src.NumBytes(), nil
-				}
-				// Server sent us a response for a request we never sent,
-				// or for which we already received a reply (e.g. aborted), an unlikely event.
+				// Server sent us a response for a request we never sent?
 				return 0, syserror.EINVAL
 			}
 
@@ -345,23 +307,8 @@ func (fd *DeviceFD) writeLocked(ctx context.Context, src usermem.IOSequence, opt
 
 // Readiness implements vfs.FileDescriptionImpl.Readiness.
 func (fd *DeviceFD) Readiness(mask waiter.EventMask) waiter.EventMask {
-	fd.mu.Lock()
-	defer fd.mu.Unlock()
-	return fd.readinessLocked(mask)
-}
-
-// readinessLocked implements checking the readiness of the fuse device while
-// locked with DeviceFD.mu.
-func (fd *DeviceFD) readinessLocked(mask waiter.EventMask) waiter.EventMask {
 	var ready waiter.EventMask
-
-	if fd.fs.umounted {
-		ready |= waiter.EventErr
-		return ready & mask
-	}
-
-	// FD is always writable.
-	ready |= waiter.EventOut
+	ready |= waiter.EventOut // FD is always writable
 	if !fd.queue.Empty() {
 		// Have reqs available, FD is readable.
 		ready |= waiter.EventIn
@@ -383,7 +330,7 @@ func (fd *DeviceFD) EventUnregister(e *waiter.Entry) {
 // Seek implements vfs.FileDescriptionImpl.Seek.
 func (fd *DeviceFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
 	// Operations on /dev/fuse don't make sense until a FUSE filesystem is mounted.
-	if fd.fs == nil {
+	if !fd.mounted {
 		return 0, syserror.EPERM
 	}
 
@@ -392,54 +339,58 @@ func (fd *DeviceFD) Seek(ctx context.Context, offset int64, whence int32) (int64
 
 // sendResponse sends a response to the waiting task (if any).
 func (fd *DeviceFD) sendResponse(ctx context.Context, fut *futureResponse) error {
-	// Signal the task waiting on a response if any.
-	defer close(fut.ch)
+	// See if the running task need to perform some action before returning.
+	// Since we just finished writing the future, we can be sure that
+	// getResponse generates a populated response.
+	if err := fd.noReceiverAction(ctx, fut.getResponse()); err != nil {
+		return err
+	}
 
 	// Signal that the queue is no longer full.
 	select {
 	case fd.fullQueueCh <- struct{}{}:
 	default:
 	}
-	fd.numActiveRequests--
-
-	if fut.async {
-		return fd.asyncCallBack(ctx, fut.getResponse())
-	}
+	fd.numActiveRequests -= 1
 
+	// Signal the task waiting on a response.
+	close(fut.ch)
 	return nil
 }
 
-// sendError sends an error response to the waiting task (if any) by calling sendResponse().
-func (fd *DeviceFD) sendError(ctx context.Context, errno int32, unique linux.FUSEOpID) error {
+// sendError sends an error response to the waiting task (if any).
+func (fd *DeviceFD) sendError(ctx context.Context, errno int32, req *Request) error {
 	// Return the error to the calling task.
 	outHdrLen := uint32((*linux.FUSEHeaderOut)(nil).SizeBytes())
 	respHdr := linux.FUSEHeaderOut{
 		Len:    outHdrLen,
 		Error:  errno,
-		Unique: unique,
+		Unique: req.hdr.Unique,
 	}
 
 	fut, ok := fd.completions[respHdr.Unique]
 	if !ok {
-		// A response for a request we never sent,
-		// or for which we already received a reply (e.g. aborted).
+		// Server sent us a response for a request we never sent?
 		return syserror.EINVAL
 	}
 	delete(fd.completions, respHdr.Unique)
 
 	fut.hdr = &respHdr
-	return fd.sendResponse(ctx, fut)
+	if err := fd.sendResponse(ctx, fut); err != nil {
+		return err
+	}
+
+	return nil
 }
 
-// asyncCallBack executes pre-defined callback function for async requests.
-// Currently used by: FUSE_INIT.
-func (fd *DeviceFD) asyncCallBack(ctx context.Context, r *Response) error {
-	switch r.opcode {
-	case linux.FUSE_INIT:
+// noReceiverAction has the calling kernel.Task do some action if its known that no
+// receiver is going to be waiting on the future channel. This is to be used by:
+// FUSE_INIT.
+func (fd *DeviceFD) noReceiverAction(ctx context.Context, r *Response) error {
+	if r.opcode == linux.FUSE_INIT {
 		creds := auth.CredentialsFromContext(ctx)
 		rootUserNs := kernel.KernelFromContext(ctx).RootUserNamespace()
 		return fd.fs.conn.InitRecv(r, creds.HasCapabilityIn(linux.CAP_SYS_ADMIN, rootUserNs))
-		// TODO(gvisor.dev/issue/3247): support async read: correctly process the response.
 	}
 
 	return nil
diff --git a/pkg/sentry/fsimpl/fuse/directory.go b/pkg/sentry/fsimpl/fuse/directory.go
deleted file mode 100644
index 798c4a6f3..000000000
--- a/pkg/sentry/fsimpl/fuse/directory.go
+++ /dev/null
@@ -1,105 +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 fuse
-
-import (
-	"sync/atomic"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/usermem"
-)
-
-type directoryFD struct {
-	fileDescription
-}
-
-// Allocate implements directoryFD.Allocate.
-func (directoryFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
-	return syserror.EISDIR
-}
-
-// PRead implements FileDescriptionImpl.PRead.
-func (directoryFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
-	return 0, syserror.EISDIR
-}
-
-// Read implements FileDescriptionImpl.Read.
-func (directoryFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
-	return 0, syserror.EISDIR
-}
-
-// PWrite implements FileDescriptionImpl.PWrite.
-func (directoryFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
-	return 0, syserror.EISDIR
-}
-
-// Write implements FileDescriptionImpl.Write.
-func (directoryFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
-	return 0, syserror.EISDIR
-}
-
-// IterDirents implements FileDescriptionImpl.IterDirents.
-func (dir *directoryFD) IterDirents(ctx context.Context, callback vfs.IterDirentsCallback) error {
-	fusefs := dir.inode().fs
-	task, creds := kernel.TaskFromContext(ctx), auth.CredentialsFromContext(ctx)
-
-	in := linux.FUSEReadIn{
-		Fh:     dir.Fh,
-		Offset: uint64(atomic.LoadInt64(&dir.off)),
-		Size:   linux.FUSE_PAGE_SIZE,
-		Flags:  dir.statusFlags(),
-	}
-
-	// TODO(gVisor.dev/issue/3404): Support FUSE_READDIRPLUS.
-	req, err := fusefs.conn.NewRequest(creds, uint32(task.ThreadID()), dir.inode().nodeID, linux.FUSE_READDIR, &in)
-	if err != nil {
-		return err
-	}
-
-	res, err := fusefs.conn.Call(task, req)
-	if err != nil {
-		return err
-	}
-	if err := res.Error(); err != nil {
-		return err
-	}
-
-	var out linux.FUSEDirents
-	if err := res.UnmarshalPayload(&out); err != nil {
-		return err
-	}
-
-	for _, fuseDirent := range out.Dirents {
-		nextOff := int64(fuseDirent.Meta.Off)
-		dirent := vfs.Dirent{
-			Name:    fuseDirent.Name,
-			Type:    uint8(fuseDirent.Meta.Type),
-			Ino:     fuseDirent.Meta.Ino,
-			NextOff: nextOff,
-		}
-
-		if err := callback.Handle(dirent); err != nil {
-			return err
-		}
-		atomic.StoreInt64(&dir.off, nextOff)
-	}
-
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/fuse/file.go b/pkg/sentry/fsimpl/fuse/file.go
deleted file mode 100644
index 991efcda4..000000000
--- a/pkg/sentry/fsimpl/fuse/file.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 fuse
-
-import (
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/usermem"
-)
-
-// fileDescription implements vfs.FileDescriptionImpl for fuse.
-type fileDescription struct {
-	vfsfd vfs.FileDescription
-	vfs.FileDescriptionDefaultImpl
-	vfs.DentryMetadataFileDescriptionImpl
-	vfs.NoLockFD
-
-	// the file handle used in userspace.
-	Fh uint64
-
-	// Nonseekable is indicate cannot perform seek on a file.
-	Nonseekable bool
-
-	// DirectIO suggest fuse to use direct io operation.
-	DirectIO bool
-
-	// OpenFlag is the flag returned by open.
-	OpenFlag uint32
-
-	// off is the file offset.
-	off int64
-}
-
-func (fd *fileDescription) dentry() *kernfs.Dentry {
-	return fd.vfsfd.Dentry().Impl().(*kernfs.Dentry)
-}
-
-func (fd *fileDescription) inode() *inode {
-	return fd.dentry().Inode().(*inode)
-}
-
-func (fd *fileDescription) filesystem() *vfs.Filesystem {
-	return fd.vfsfd.VirtualDentry().Mount().Filesystem()
-}
-
-func (fd *fileDescription) statusFlags() uint32 {
-	return fd.vfsfd.StatusFlags()
-}
-
-// Release implements vfs.FileDescriptionImpl.Release.
-func (fd *fileDescription) Release(ctx context.Context) {
-	// no need to release if FUSE server doesn't implement Open.
-	conn := fd.inode().fs.conn
-	if conn.noOpen {
-		return
-	}
-
-	in := linux.FUSEReleaseIn{
-		Fh:    fd.Fh,
-		Flags: fd.statusFlags(),
-	}
-	// TODO(gvisor.dev/issue/3245): add logic when we support file lock owner.
-	var opcode linux.FUSEOpcode
-	if fd.inode().Mode().IsDir() {
-		opcode = linux.FUSE_RELEASEDIR
-	} else {
-		opcode = linux.FUSE_RELEASE
-	}
-	kernelTask := kernel.TaskFromContext(ctx)
-	// ignoring errors and FUSE server reply is analogous to Linux's behavior.
-	req, err := conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(kernelTask.ThreadID()), fd.inode().nodeID, opcode, &in)
-	if err != nil {
-		// No way to invoke Call() with an errored request.
-		return
-	}
-	req.noReply = true
-	conn.CallAsync(kernelTask, req)
-}
-
-// PRead implements vfs.FileDescriptionImpl.PRead.
-func (fd *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
-	return 0, nil
-}
-
-// Read implements vfs.FileDescriptionImpl.Read.
-func (fd *fileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
-	return 0, nil
-}
-
-// PWrite implements vfs.FileDescriptionImpl.PWrite.
-func (fd *fileDescription) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
-	return 0, nil
-}
-
-// Write implements vfs.FileDescriptionImpl.Write.
-func (fd *fileDescription) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
-	return 0, nil
-}
-
-// Seek implements vfs.FileDescriptionImpl.Seek.
-func (fd *fileDescription) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
-	return 0, nil
-}
-
-// Stat implements vfs.FileDescriptionImpl.Stat.
-func (fd *fileDescription) Stat(ctx context.Context, opts vfs.StatOptions) (linux.Statx, error) {
-	fs := fd.filesystem()
-	inode := fd.inode()
-	return inode.Stat(ctx, fs, opts)
-}
-
-// SetStat implements vfs.FileDescriptionImpl.SetStat.
-func (fd *fileDescription) SetStat(ctx context.Context, opts vfs.SetStatOptions) error {
-	fs := fd.filesystem()
-	creds := auth.CredentialsFromContext(ctx)
-	return fd.inode().setAttr(ctx, fs, creds, opts, true, fd.Fh)
-}
diff --git a/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go b/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
index 6c82dce30..f72fe342e 100644
--- a/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
+++ b/pkg/sentry/fsimpl/fuse/fuse_state_autogen.go
@@ -6,191 +6,179 @@ import (
 	"gvisor.dev/gvisor/pkg/state"
 )
 
-func (x *inodeRefs) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.inodeRefs"
+func (x *Request) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.Request"
 }
 
-func (x *inodeRefs) StateFields() []string {
+func (x *Request) StateFields() []string {
 	return []string{
-		"refCount",
+		"requestEntry",
+		"id",
+		"hdr",
+		"data",
 	}
 }
 
-func (x *inodeRefs) beforeSave() {}
+func (x *Request) beforeSave() {}
 
-func (x *inodeRefs) StateSave(m state.Sink) {
+func (x *Request) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.refCount)
+	m.Save(0, &x.requestEntry)
+	m.Save(1, &x.id)
+	m.Save(2, &x.hdr)
+	m.Save(3, &x.data)
 }
 
-func (x *inodeRefs) afterLoad() {}
+func (x *Request) afterLoad() {}
 
-func (x *inodeRefs) StateLoad(m state.Source) {
-	m.Load(0, &x.refCount)
+func (x *Request) StateLoad(m state.Source) {
+	m.Load(0, &x.requestEntry)
+	m.Load(1, &x.id)
+	m.Load(2, &x.hdr)
+	m.Load(3, &x.data)
 }
 
-func (x *requestList) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.requestList"
+func (x *Response) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.Response"
 }
 
-func (x *requestList) StateFields() []string {
+func (x *Response) StateFields() []string {
 	return []string{
-		"head",
-		"tail",
+		"opcode",
+		"hdr",
+		"data",
 	}
 }
 
-func (x *requestList) beforeSave() {}
+func (x *Response) beforeSave() {}
 
-func (x *requestList) StateSave(m state.Sink) {
+func (x *Response) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.head)
-	m.Save(1, &x.tail)
+	m.Save(0, &x.opcode)
+	m.Save(1, &x.hdr)
+	m.Save(2, &x.data)
 }
 
-func (x *requestList) afterLoad() {}
+func (x *Response) afterLoad() {}
 
-func (x *requestList) StateLoad(m state.Source) {
-	m.Load(0, &x.head)
-	m.Load(1, &x.tail)
+func (x *Response) StateLoad(m state.Source) {
+	m.Load(0, &x.opcode)
+	m.Load(1, &x.hdr)
+	m.Load(2, &x.data)
 }
 
-func (x *requestEntry) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.requestEntry"
+func (x *futureResponse) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.futureResponse"
 }
 
-func (x *requestEntry) StateFields() []string {
+func (x *futureResponse) StateFields() []string {
 	return []string{
-		"next",
-		"prev",
+		"opcode",
+		"ch",
+		"hdr",
+		"data",
 	}
 }
 
-func (x *requestEntry) beforeSave() {}
+func (x *futureResponse) beforeSave() {}
 
-func (x *requestEntry) StateSave(m state.Sink) {
+func (x *futureResponse) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.next)
-	m.Save(1, &x.prev)
+	m.Save(0, &x.opcode)
+	m.Save(1, &x.ch)
+	m.Save(2, &x.hdr)
+	m.Save(3, &x.data)
 }
 
-func (x *requestEntry) afterLoad() {}
+func (x *futureResponse) afterLoad() {}
 
-func (x *requestEntry) StateLoad(m state.Source) {
-	m.Load(0, &x.next)
-	m.Load(1, &x.prev)
+func (x *futureResponse) StateLoad(m state.Source) {
+	m.Load(0, &x.opcode)
+	m.Load(1, &x.ch)
+	m.Load(2, &x.hdr)
+	m.Load(3, &x.data)
 }
 
-func (x *Request) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.Request"
+func (x *inodeRefs) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.inodeRefs"
 }
 
-func (x *Request) StateFields() []string {
+func (x *inodeRefs) StateFields() []string {
 	return []string{
-		"requestEntry",
-		"id",
-		"hdr",
-		"data",
-		"payload",
-		"async",
-		"noReply",
+		"refCount",
 	}
 }
 
-func (x *Request) beforeSave() {}
+func (x *inodeRefs) beforeSave() {}
 
-func (x *Request) StateSave(m state.Sink) {
+func (x *inodeRefs) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.requestEntry)
-	m.Save(1, &x.id)
-	m.Save(2, &x.hdr)
-	m.Save(3, &x.data)
-	m.Save(4, &x.payload)
-	m.Save(5, &x.async)
-	m.Save(6, &x.noReply)
+	m.Save(0, &x.refCount)
 }
 
-func (x *Request) afterLoad() {}
+func (x *inodeRefs) afterLoad() {}
 
-func (x *Request) StateLoad(m state.Source) {
-	m.Load(0, &x.requestEntry)
-	m.Load(1, &x.id)
-	m.Load(2, &x.hdr)
-	m.Load(3, &x.data)
-	m.Load(4, &x.payload)
-	m.Load(5, &x.async)
-	m.Load(6, &x.noReply)
+func (x *inodeRefs) StateLoad(m state.Source) {
+	m.Load(0, &x.refCount)
 }
 
-func (x *futureResponse) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.futureResponse"
+func (x *requestList) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.requestList"
 }
 
-func (x *futureResponse) StateFields() []string {
+func (x *requestList) StateFields() []string {
 	return []string{
-		"opcode",
-		"ch",
-		"hdr",
-		"data",
-		"async",
+		"head",
+		"tail",
 	}
 }
 
-func (x *futureResponse) beforeSave() {}
+func (x *requestList) beforeSave() {}
 
-func (x *futureResponse) StateSave(m state.Sink) {
+func (x *requestList) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.opcode)
-	m.Save(1, &x.ch)
-	m.Save(2, &x.hdr)
-	m.Save(3, &x.data)
-	m.Save(4, &x.async)
+	m.Save(0, &x.head)
+	m.Save(1, &x.tail)
 }
 
-func (x *futureResponse) afterLoad() {}
+func (x *requestList) afterLoad() {}
 
-func (x *futureResponse) StateLoad(m state.Source) {
-	m.Load(0, &x.opcode)
-	m.Load(1, &x.ch)
-	m.Load(2, &x.hdr)
-	m.Load(3, &x.data)
-	m.Load(4, &x.async)
+func (x *requestList) StateLoad(m state.Source) {
+	m.Load(0, &x.head)
+	m.Load(1, &x.tail)
 }
 
-func (x *Response) StateTypeName() string {
-	return "pkg/sentry/fsimpl/fuse.Response"
+func (x *requestEntry) StateTypeName() string {
+	return "pkg/sentry/fsimpl/fuse.requestEntry"
 }
 
-func (x *Response) StateFields() []string {
+func (x *requestEntry) StateFields() []string {
 	return []string{
-		"opcode",
-		"hdr",
-		"data",
+		"next",
+		"prev",
 	}
 }
 
-func (x *Response) beforeSave() {}
+func (x *requestEntry) beforeSave() {}
 
-func (x *Response) StateSave(m state.Sink) {
+func (x *requestEntry) StateSave(m state.Sink) {
 	x.beforeSave()
-	m.Save(0, &x.opcode)
-	m.Save(1, &x.hdr)
-	m.Save(2, &x.data)
+	m.Save(0, &x.next)
+	m.Save(1, &x.prev)
 }
 
-func (x *Response) afterLoad() {}
+func (x *requestEntry) afterLoad() {}
 
-func (x *Response) StateLoad(m state.Source) {
-	m.Load(0, &x.opcode)
-	m.Load(1, &x.hdr)
-	m.Load(2, &x.data)
+func (x *requestEntry) StateLoad(m state.Source) {
+	m.Load(0, &x.next)
+	m.Load(1, &x.prev)
 }
 
 func init() {
+	state.Register((*Request)(nil))
+	state.Register((*Response)(nil))
+	state.Register((*futureResponse)(nil))
 	state.Register((*inodeRefs)(nil))
 	state.Register((*requestList)(nil))
 	state.Register((*requestEntry)(nil))
-	state.Register((*Request)(nil))
-	state.Register((*futureResponse)(nil))
-	state.Register((*Response)(nil))
 }
diff --git a/pkg/sentry/fsimpl/fuse/fusefs.go b/pkg/sentry/fsimpl/fuse/fusefs.go
index 402dabe5a..810819ae4 100644
--- a/pkg/sentry/fsimpl/fuse/fusefs.go
+++ b/pkg/sentry/fsimpl/fuse/fusefs.go
@@ -16,10 +16,7 @@
 package fuse
 
 import (
-	"math"
 	"strconv"
-	"sync"
-	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
@@ -29,17 +26,11 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/waiter"
-	"gvisor.dev/gvisor/tools/go_marshal/marshal"
 )
 
 // Name is the default filesystem name.
 const Name = "fuse"
 
-// maxActiveRequestsDefault is the default setting controlling the upper bound
-// on the number of active requests at any given time.
-const maxActiveRequestsDefault = 10000
-
 // FilesystemType implements vfs.FilesystemType.
 type FilesystemType struct{}
 
@@ -65,11 +56,6 @@ type filesystemOptions struct {
 	// exist at any time. Any further requests will block when trying to
 	// Call the server.
 	maxActiveRequests uint64
-
-	// maxRead is the max number of bytes to read,
-	// specified as "max_read" in fs parameters.
-	// If not specified by user, use math.MaxUint32 as default value.
-	maxRead uint32
 }
 
 // filesystem implements vfs.FilesystemImpl.
@@ -83,9 +69,6 @@ type filesystem struct {
 
 	// opts is the options the fusefs is initialized with.
 	opts *filesystemOptions
-
-	// umounted is true if filesystem.Release() has been called.
-	umounted bool
 }
 
 // Name implements vfs.FilesystemType.Name.
@@ -159,29 +142,14 @@ func (fsType FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
 	// Set the maxInFlightRequests option.
 	fsopts.maxActiveRequests = maxActiveRequestsDefault
 
-	if maxReadStr, ok := mopts["max_read"]; ok {
-		delete(mopts, "max_read")
-		maxRead, err := strconv.ParseUint(maxReadStr, 10, 32)
-		if err != nil {
-			log.Warningf("%s.GetFilesystem: invalid max_read: max_read=%s", fsType.Name(), maxReadStr)
-			return nil, nil, syserror.EINVAL
-		}
-		if maxRead < fuseMinMaxRead {
-			maxRead = fuseMinMaxRead
-		}
-		fsopts.maxRead = uint32(maxRead)
-	} else {
-		fsopts.maxRead = math.MaxUint32
-	}
-
 	// Check for unparsed options.
 	if len(mopts) != 0 {
-		log.Warningf("%s.GetFilesystem: unsupported or unknown options: %v", fsType.Name(), mopts)
+		log.Warningf("%s.GetFilesystem: unknown options: %v", fsType.Name(), mopts)
 		return nil, nil, syserror.EINVAL
 	}
 
 	// Create a new FUSE filesystem.
-	fs, err := newFUSEFilesystem(ctx, devMinor, &fsopts, fuseFd)
+	fs, err := NewFUSEFilesystem(ctx, devMinor, &fsopts, fuseFd)
 	if err != nil {
 		log.Warningf("%s.NewFUSEFilesystem: failed with error: %v", fsType.Name(), err)
 		return nil, nil, err
@@ -197,27 +165,26 @@ func (fsType FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.Virt
 	}
 
 	// root is the fusefs root directory.
-	root := fs.newRootInode(creds, fsopts.rootMode)
+	root := fs.newInode(creds, fsopts.rootMode)
 
 	return fs.VFSFilesystem(), root.VFSDentry(), nil
 }
 
-// newFUSEFilesystem creates a new FUSE filesystem.
-func newFUSEFilesystem(ctx context.Context, devMinor uint32, opts *filesystemOptions, device *vfs.FileDescription) (*filesystem, error) {
-	conn, err := newFUSEConnection(ctx, device, opts)
+// NewFUSEFilesystem creates a new FUSE filesystem.
+func NewFUSEFilesystem(ctx context.Context, devMinor uint32, opts *filesystemOptions, device *vfs.FileDescription) (*filesystem, error) {
+	fs := &filesystem{
+		devMinor: devMinor,
+		opts:     opts,
+	}
+
+	conn, err := newFUSEConnection(ctx, device, opts.maxActiveRequests)
 	if err != nil {
 		log.Warningf("fuse.NewFUSEFilesystem: NewFUSEConnection failed with error: %v", err)
 		return nil, syserror.EINVAL
 	}
 
+	fs.conn = conn
 	fuseFD := device.Impl().(*DeviceFD)
-
-	fs := &filesystem{
-		devMinor: devMinor,
-		opts:     opts,
-		conn:     conn,
-	}
-
 	fuseFD.fs = fs
 
 	return fs, nil
@@ -225,14 +192,6 @@ func newFUSEFilesystem(ctx context.Context, devMinor uint32, opts *filesystemOpt
 
 // Release implements vfs.FilesystemImpl.Release.
 func (fs *filesystem) Release(ctx context.Context) {
-	fs.umounted = true
-	fs.conn.Abort(ctx)
-
-	fs.conn.fd.mu.Lock()
-	// Notify all the waiters on this fd.
-	fs.conn.fd.waitQueue.Notify(waiter.EventIn)
-	fs.conn.fd.mu.Unlock()
-
 	fs.Filesystem.VFSFilesystem().VirtualFilesystem().PutAnonBlockDevMinor(fs.devMinor)
 	fs.Filesystem.Release(ctx)
 }
@@ -246,49 +205,14 @@ type inode struct {
 	kernfs.InodeNotSymlink
 	kernfs.OrderedChildren
 
-	dentry kernfs.Dentry
-
-	// the owning filesystem. fs is immutable.
-	fs *filesystem
-
-	// metaDataMu protects the metadata of this inode.
-	metadataMu sync.Mutex
-
-	nodeID uint64
-
 	locks vfs.FileLocks
 
-	// size of the file.
-	size uint64
-
-	// attributeVersion is the version of inode's attributes.
-	attributeVersion uint64
-
-	// attributeTime is the remaining vaild time of attributes.
-	attributeTime uint64
-
-	// version of the inode.
-	version uint64
-
-	// link is result of following a symbolic link.
-	link string
-}
-
-func (fs *filesystem) newRootInode(creds *auth.Credentials, mode linux.FileMode) *kernfs.Dentry {
-	i := &inode{fs: fs}
-	i.InodeAttrs.Init(creds, linux.UNNAMED_MAJOR, fs.devMinor, 1, linux.ModeDirectory|0755)
-	i.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
-	i.dentry.Init(i)
-	i.nodeID = 1
-
-	return &i.dentry
+	dentry kernfs.Dentry
 }
 
-func (fs *filesystem) newInode(nodeID uint64, attr linux.FUSEAttr) *kernfs.Dentry {
-	i := &inode{fs: fs, nodeID: nodeID}
-	creds := auth.Credentials{EffectiveKGID: auth.KGID(attr.UID), EffectiveKUID: auth.KUID(attr.UID)}
-	i.InodeAttrs.Init(&creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), linux.FileMode(attr.Mode))
-	atomic.StoreUint64(&i.size, attr.Size)
+func (fs *filesystem) newInode(creds *auth.Credentials, mode linux.FileMode) *kernfs.Dentry {
+	i := &inode{}
+	i.InodeAttrs.Init(creds, linux.UNNAMED_MAJOR, fs.devMinor, fs.NextIno(), linux.ModeDirectory|0755)
 	i.OrderedChildren.Init(kernfs.OrderedChildrenOptions{})
 	i.EnableLeakCheck()
 	i.dentry.Init(i)
@@ -298,301 +222,13 @@ func (fs *filesystem) newInode(nodeID uint64, attr linux.FUSEAttr) *kernfs.Dentr
 
 // Open implements kernfs.Inode.Open.
 func (i *inode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
-	isDir := i.InodeAttrs.Mode().IsDir()
-	// return error if specified to open directory but inode is not a directory.
-	if !isDir && opts.Mode.IsDir() {
-		return nil, syserror.ENOTDIR
-	}
-	if opts.Flags&linux.O_LARGEFILE == 0 && atomic.LoadUint64(&i.size) > linux.MAX_NON_LFS {
-		return nil, syserror.EOVERFLOW
-	}
-
-	var fd *fileDescription
-	var fdImpl vfs.FileDescriptionImpl
-	if isDir {
-		directoryFD := &directoryFD{}
-		fd = &(directoryFD.fileDescription)
-		fdImpl = directoryFD
-	} else {
-		regularFD := &regularFileFD{}
-		fd = &(regularFD.fileDescription)
-		fdImpl = regularFD
-	}
-	// FOPEN_KEEP_CACHE is the defualt flag for noOpen.
-	fd.OpenFlag = linux.FOPEN_KEEP_CACHE
-
-	// Only send open request when FUSE server support open or is opening a directory.
-	if !i.fs.conn.noOpen || isDir {
-		kernelTask := kernel.TaskFromContext(ctx)
-		if kernelTask == nil {
-			log.Warningf("fusefs.Inode.Open: couldn't get kernel task from context")
-			return nil, syserror.EINVAL
-		}
-
-		// Build the request.
-		var opcode linux.FUSEOpcode
-		if isDir {
-			opcode = linux.FUSE_OPENDIR
-		} else {
-			opcode = linux.FUSE_OPEN
-		}
-
-		in := linux.FUSEOpenIn{Flags: opts.Flags & ^uint32(linux.O_CREAT|linux.O_EXCL|linux.O_NOCTTY)}
-		if !i.fs.conn.atomicOTrunc {
-			in.Flags &= ^uint32(linux.O_TRUNC)
-		}
-
-		req, err := i.fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(kernelTask.ThreadID()), i.nodeID, opcode, &in)
-		if err != nil {
-			return nil, err
-		}
-
-		// Send the request and receive the reply.
-		res, err := i.fs.conn.Call(kernelTask, req)
-		if err != nil {
-			return nil, err
-		}
-		if err := res.Error(); err == syserror.ENOSYS && !isDir {
-			i.fs.conn.noOpen = true
-		} else if err != nil {
-			return nil, err
-		} else {
-			out := linux.FUSEOpenOut{}
-			if err := res.UnmarshalPayload(&out); err != nil {
-				return nil, err
-			}
-
-			// Process the reply.
-			fd.OpenFlag = out.OpenFlag
-			if isDir {
-				fd.OpenFlag &= ^uint32(linux.FOPEN_DIRECT_IO)
-			}
-
-			fd.Fh = out.Fh
-		}
-	}
-
-	// TODO(gvisor.dev/issue/3234): invalidate mmap after implemented it for FUSE Inode
-	fd.DirectIO = fd.OpenFlag&linux.FOPEN_DIRECT_IO != 0
-	fdOptions := &vfs.FileDescriptionOptions{}
-	if fd.OpenFlag&linux.FOPEN_NONSEEKABLE != 0 {
-		fdOptions.DenyPRead = true
-		fdOptions.DenyPWrite = true
-		fd.Nonseekable = true
-	}
-
-	// If we don't send SETATTR before open (which is indicated by atomicOTrunc)
-	// and O_TRUNC is set, update the inode's version number and clean existing data
-	// by setting the file size to 0.
-	if i.fs.conn.atomicOTrunc && opts.Flags&linux.O_TRUNC != 0 {
-		i.fs.conn.mu.Lock()
-		i.fs.conn.attributeVersion++
-		i.attributeVersion = i.fs.conn.attributeVersion
-		atomic.StoreUint64(&i.size, 0)
-		i.fs.conn.mu.Unlock()
-		i.attributeTime = 0
-	}
-
-	if err := fd.vfsfd.Init(fdImpl, opts.Flags, rp.Mount(), vfsd, fdOptions); err != nil {
-		return nil, err
-	}
-	return &fd.vfsfd, nil
-}
-
-// Lookup implements kernfs.Inode.Lookup.
-func (i *inode) Lookup(ctx context.Context, name string) (*vfs.Dentry, error) {
-	in := linux.FUSELookupIn{Name: name}
-	return i.newEntry(ctx, name, 0, linux.FUSE_LOOKUP, &in)
-}
-
-// IterDirents implements kernfs.Inode.IterDirents.
-func (*inode) IterDirents(ctx context.Context, callback vfs.IterDirentsCallback, offset, relOffset int64) (int64, error) {
-	return offset, nil
-}
-
-// Valid implements kernfs.Inode.Valid.
-func (*inode) Valid(ctx context.Context) bool {
-	return true
-}
-
-// NewFile implements kernfs.Inode.NewFile.
-func (i *inode) NewFile(ctx context.Context, name string, opts vfs.OpenOptions) (*vfs.Dentry, error) {
-	kernelTask := kernel.TaskFromContext(ctx)
-	if kernelTask == nil {
-		log.Warningf("fusefs.Inode.NewFile: couldn't get kernel task from context", i.nodeID)
-		return nil, syserror.EINVAL
-	}
-	in := linux.FUSECreateIn{
-		CreateMeta: linux.FUSECreateMeta{
-			Flags: opts.Flags,
-			Mode:  uint32(opts.Mode) | linux.S_IFREG,
-			Umask: uint32(kernelTask.FSContext().Umask()),
-		},
-		Name: name,
-	}
-	return i.newEntry(ctx, name, linux.S_IFREG, linux.FUSE_CREATE, &in)
-}
-
-// NewNode implements kernfs.Inode.NewNode.
-func (i *inode) NewNode(ctx context.Context, name string, opts vfs.MknodOptions) (*vfs.Dentry, error) {
-	in := linux.FUSEMknodIn{
-		MknodMeta: linux.FUSEMknodMeta{
-			Mode:  uint32(opts.Mode),
-			Rdev:  linux.MakeDeviceID(uint16(opts.DevMajor), opts.DevMinor),
-			Umask: uint32(kernel.TaskFromContext(ctx).FSContext().Umask()),
-		},
-		Name: name,
-	}
-	return i.newEntry(ctx, name, opts.Mode.FileType(), linux.FUSE_MKNOD, &in)
-}
-
-// NewSymlink implements kernfs.Inode.NewSymlink.
-func (i *inode) NewSymlink(ctx context.Context, name, target string) (*vfs.Dentry, error) {
-	in := linux.FUSESymLinkIn{
-		Name:   name,
-		Target: target,
-	}
-	return i.newEntry(ctx, name, linux.S_IFLNK, linux.FUSE_SYMLINK, &in)
-}
-
-// Unlink implements kernfs.Inode.Unlink.
-func (i *inode) Unlink(ctx context.Context, name string, child *vfs.Dentry) error {
-	kernelTask := kernel.TaskFromContext(ctx)
-	if kernelTask == nil {
-		log.Warningf("fusefs.Inode.newEntry: couldn't get kernel task from context", i.nodeID)
-		return syserror.EINVAL
-	}
-	in := linux.FUSEUnlinkIn{Name: name}
-	req, err := i.fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(kernelTask.ThreadID()), i.nodeID, linux.FUSE_UNLINK, &in)
-	if err != nil {
-		return err
-	}
-	res, err := i.fs.conn.Call(kernelTask, req)
+	fd, err := kernfs.NewGenericDirectoryFD(rp.Mount(), vfsd, &i.OrderedChildren, &i.locks, &opts, kernfs.GenericDirectoryFDOptions{
+		SeekEnd: kernfs.SeekEndStaticEntries,
+	})
 	if err != nil {
-		return err
-	}
-	// only return error, discard res.
-	if err := res.Error(); err != nil {
-		return err
-	}
-	return i.dentry.RemoveChildLocked(name, child)
-}
-
-// NewDir implements kernfs.Inode.NewDir.
-func (i *inode) NewDir(ctx context.Context, name string, opts vfs.MkdirOptions) (*vfs.Dentry, error) {
-	in := linux.FUSEMkdirIn{
-		MkdirMeta: linux.FUSEMkdirMeta{
-			Mode:  uint32(opts.Mode),
-			Umask: uint32(kernel.TaskFromContext(ctx).FSContext().Umask()),
-		},
-		Name: name,
-	}
-	return i.newEntry(ctx, name, linux.S_IFDIR, linux.FUSE_MKDIR, &in)
-}
-
-// RmDir implements kernfs.Inode.RmDir.
-func (i *inode) RmDir(ctx context.Context, name string, child *vfs.Dentry) error {
-	fusefs := i.fs
-	task, creds := kernel.TaskFromContext(ctx), auth.CredentialsFromContext(ctx)
-
-	in := linux.FUSERmDirIn{Name: name}
-	req, err := fusefs.conn.NewRequest(creds, uint32(task.ThreadID()), i.nodeID, linux.FUSE_RMDIR, &in)
-	if err != nil {
-		return err
-	}
-
-	res, err := i.fs.conn.Call(task, req)
-	if err != nil {
-		return err
-	}
-	if err := res.Error(); err != nil {
-		return err
-	}
-
-	// TODO(Before merging): When creating new nodes, should we add nodes to the ordered children?
-	// If so we'll probably need to call this. We will also need to add them with the writable flag when
-	// appropriate.
-	// return i.OrderedChildren.RmDir(ctx, name, child)
-
-	return nil
-}
-
-// newEntry calls FUSE server for entry creation and allocates corresponding entry according to response.
-// Shared by FUSE_MKNOD, FUSE_MKDIR, FUSE_SYMLINK, FUSE_LINK and FUSE_LOOKUP.
-func (i *inode) newEntry(ctx context.Context, name string, fileType linux.FileMode, opcode linux.FUSEOpcode, payload marshal.Marshallable) (*vfs.Dentry, error) {
-	kernelTask := kernel.TaskFromContext(ctx)
-	if kernelTask == nil {
-		log.Warningf("fusefs.Inode.newEntry: couldn't get kernel task from context", i.nodeID)
-		return nil, syserror.EINVAL
-	}
-	req, err := i.fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(kernelTask.ThreadID()), i.nodeID, opcode, payload)
-	if err != nil {
-		return nil, err
-	}
-	res, err := i.fs.conn.Call(kernelTask, req)
-	if err != nil {
-		return nil, err
-	}
-	if err := res.Error(); err != nil {
 		return nil, err
 	}
-	out := linux.FUSEEntryOut{}
-	if err := res.UnmarshalPayload(&out); err != nil {
-		return nil, err
-	}
-	if opcode != linux.FUSE_LOOKUP && ((out.Attr.Mode&linux.S_IFMT)^uint32(fileType) != 0 || out.NodeID == 0 || out.NodeID == linux.FUSE_ROOT_ID) {
-		return nil, syserror.EIO
-	}
-	child := i.fs.newInode(out.NodeID, out.Attr)
-	if opcode == linux.FUSE_LOOKUP {
-		i.dentry.InsertChildLocked(name, child)
-	} else {
-		i.dentry.InsertChild(name, child)
-	}
-	return child.VFSDentry(), nil
-}
-
-// Getlink implements kernfs.Inode.Getlink.
-func (i *inode) Getlink(ctx context.Context, mnt *vfs.Mount) (vfs.VirtualDentry, string, error) {
-	path, err := i.Readlink(ctx, mnt)
-	return vfs.VirtualDentry{}, path, err
-}
-
-// Readlink implements kernfs.Inode.Readlink.
-func (i *inode) Readlink(ctx context.Context, mnt *vfs.Mount) (string, error) {
-	if i.Mode().FileType()&linux.S_IFLNK == 0 {
-		return "", syserror.EINVAL
-	}
-	if len(i.link) == 0 {
-		kernelTask := kernel.TaskFromContext(ctx)
-		if kernelTask == nil {
-			log.Warningf("fusefs.Inode.Readlink: couldn't get kernel task from context")
-			return "", syserror.EINVAL
-		}
-		req, err := i.fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(kernelTask.ThreadID()), i.nodeID, linux.FUSE_READLINK, &linux.FUSEEmptyIn{})
-		if err != nil {
-			return "", err
-		}
-		res, err := i.fs.conn.Call(kernelTask, req)
-		if err != nil {
-			return "", err
-		}
-		i.link = string(res.data[res.hdr.SizeBytes():])
-		if !mnt.Options().ReadOnly {
-			i.attributeTime = 0
-		}
-	}
-	return i.link, nil
-}
-
-// getFUSEAttr returns a linux.FUSEAttr of this inode stored in local cache.
-// TODO(gvisor.dev/issue/3679): Add support for other fields.
-func (i *inode) getFUSEAttr() linux.FUSEAttr {
-	return linux.FUSEAttr{
-		Ino:  i.Ino(),
-		Size: atomic.LoadUint64(&i.size),
-		Mode: uint32(i.Mode()),
-	}
+	return fd.VFSFileDescription(), nil
 }
 
 // statFromFUSEAttr makes attributes from linux.FUSEAttr to linux.Statx. The
@@ -648,89 +284,47 @@ func statFromFUSEAttr(attr linux.FUSEAttr, mask, devMinor uint32) linux.Statx {
 	return stat
 }
 
-// getAttr gets the attribute of this inode by issuing a FUSE_GETATTR request
-// or read from local cache. It updates the corresponding attributes if
-// necessary.
-func (i *inode) getAttr(ctx context.Context, fs *vfs.Filesystem, opts vfs.StatOptions, flags uint32, fh uint64) (linux.FUSEAttr, error) {
-	attributeVersion := atomic.LoadUint64(&i.fs.conn.attributeVersion)
-
-	// TODO(gvisor.dev/issue/3679): send the request only if
-	// - invalid local cache for fields specified in the opts.Mask
-	// - forced update
-	// - i.attributeTime expired
-	// If local cache is still valid, return local cache.
-	// Currently we always send a request,
-	// and we always set the metadata with the new result,
-	// unless attributeVersion has changed.
-
-	task := kernel.TaskFromContext(ctx)
+// Stat implements kernfs.Inode.Stat.
+func (i *inode) Stat(ctx context.Context, fs *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, error) {
+	fusefs := fs.Impl().(*filesystem)
+	conn := fusefs.conn
+	task, creds := kernel.TaskFromContext(ctx), auth.CredentialsFromContext(ctx)
 	if task == nil {
 		log.Warningf("couldn't get kernel task from context")
-		return linux.FUSEAttr{}, syserror.EINVAL
+		return linux.Statx{}, syserror.EINVAL
 	}
 
-	creds := auth.CredentialsFromContext(ctx)
-
-	in := linux.FUSEGetAttrIn{
-		GetAttrFlags: flags,
-		Fh:           fh,
-	}
-	req, err := i.fs.conn.NewRequest(creds, uint32(task.ThreadID()), i.nodeID, linux.FUSE_GETATTR, &in)
+	var in linux.FUSEGetAttrIn
+	// We don't set any attribute in the request, because in VFS2 fstat(2) will
+	// finally be translated into vfs.FilesystemImpl.StatAt() (see
+	// pkg/sentry/syscalls/linux/vfs2/stat.go), resulting in the same flow
+	// as stat(2). Thus GetAttrFlags and Fh variable will never be used in VFS2.
+	req, err := conn.NewRequest(creds, uint32(task.ThreadID()), i.Ino(), linux.FUSE_GETATTR, &in)
 	if err != nil {
-		return linux.FUSEAttr{}, err
+		return linux.Statx{}, err
 	}
 
-	res, err := i.fs.conn.Call(task, req)
+	res, err := conn.Call(task, req)
 	if err != nil {
-		return linux.FUSEAttr{}, err
+		return linux.Statx{}, err
 	}
 	if err := res.Error(); err != nil {
-		return linux.FUSEAttr{}, err
+		return linux.Statx{}, err
 	}
 
 	var out linux.FUSEGetAttrOut
 	if err := res.UnmarshalPayload(&out); err != nil {
-		return linux.FUSEAttr{}, err
-	}
-
-	// Local version is newer, return the local one.
-	// Skip the update.
-	if attributeVersion != 0 && atomic.LoadUint64(&i.attributeVersion) > attributeVersion {
-		return i.getFUSEAttr(), nil
+		return linux.Statx{}, err
 	}
 
-	// Set the metadata of kernfs.InodeAttrs.
-	if err := i.SetInodeStat(ctx, fs, creds, vfs.SetStatOptions{
-		Stat: statFromFUSEAttr(out.Attr, linux.STATX_ALL, i.fs.devMinor),
+	// Set all metadata into kernfs.InodeAttrs.
+	if err := i.SetStat(ctx, fs, creds, vfs.SetStatOptions{
+		Stat: statFromFUSEAttr(out.Attr, linux.STATX_ALL, fusefs.devMinor),
 	}); err != nil {
-		return linux.FUSEAttr{}, err
-	}
-
-	// Set the size if no error (after SetStat() check).
-	atomic.StoreUint64(&i.size, out.Attr.Size)
-
-	return out.Attr, nil
-}
-
-// reviseAttr attempts to update the attributes for internal purposes
-// by calling getAttr with a pre-specified mask.
-// Used by read, write, lseek.
-func (i *inode) reviseAttr(ctx context.Context, flags uint32, fh uint64) error {
-	// Never need atime for internal purposes.
-	_, err := i.getAttr(ctx, i.fs.VFSFilesystem(), vfs.StatOptions{
-		Mask: linux.STATX_BASIC_STATS &^ linux.STATX_ATIME,
-	}, flags, fh)
-	return err
-}
-
-// Stat implements kernfs.Inode.Stat.
-func (i *inode) Stat(ctx context.Context, fs *vfs.Filesystem, opts vfs.StatOptions) (linux.Statx, error) {
-	attr, err := i.getAttr(ctx, fs, opts, 0, 0)
-	if err != nil {
 		return linux.Statx{}, err
 	}
 
-	return statFromFUSEAttr(attr, opts.Mask, i.fs.devMinor), nil
+	return statFromFUSEAttr(out.Attr, opts.Mask, fusefs.devMinor), nil
 }
 
 // DecRef implements kernfs.Inode.
@@ -743,84 +337,3 @@ func (i *inode) StatFS(ctx context.Context, fs *vfs.Filesystem) (linux.Statfs, e
 	// TODO(gvisor.dev/issues/3413): Complete the implementation of statfs.
 	return vfs.GenericStatFS(linux.FUSE_SUPER_MAGIC), nil
 }
-
-// fattrMaskFromStats converts vfs.SetStatOptions.Stat.Mask to linux stats mask
-// aligned with the attribute mask defined in include/linux/fs.h.
-func fattrMaskFromStats(mask uint32) uint32 {
-	var fuseAttrMask uint32
-	maskMap := map[uint32]uint32{
-		linux.STATX_MODE:  linux.FATTR_MODE,
-		linux.STATX_UID:   linux.FATTR_UID,
-		linux.STATX_GID:   linux.FATTR_GID,
-		linux.STATX_SIZE:  linux.FATTR_SIZE,
-		linux.STATX_ATIME: linux.FATTR_ATIME,
-		linux.STATX_MTIME: linux.FATTR_MTIME,
-		linux.STATX_CTIME: linux.FATTR_CTIME,
-	}
-	for statxMask, fattrMask := range maskMap {
-		if mask&statxMask != 0 {
-			fuseAttrMask |= fattrMask
-		}
-	}
-	return fuseAttrMask
-}
-
-// SetStat implements kernfs.Inode.SetStat.
-func (i *inode) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
-	return i.setAttr(ctx, fs, creds, opts, false, 0)
-}
-
-func (i *inode) setAttr(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions, useFh bool, fh uint64) error {
-	conn := i.fs.conn
-	task := kernel.TaskFromContext(ctx)
-	if task == nil {
-		log.Warningf("couldn't get kernel task from context")
-		return syserror.EINVAL
-	}
-
-	// We should retain the original file type when assigning new mode.
-	fileType := uint16(i.Mode()) & linux.S_IFMT
-	fattrMask := fattrMaskFromStats(opts.Stat.Mask)
-	if useFh {
-		fattrMask |= linux.FATTR_FH
-	}
-	in := linux.FUSESetAttrIn{
-		Valid:     fattrMask,
-		Fh:        fh,
-		Size:      opts.Stat.Size,
-		Atime:     uint64(opts.Stat.Atime.Sec),
-		Mtime:     uint64(opts.Stat.Mtime.Sec),
-		Ctime:     uint64(opts.Stat.Ctime.Sec),
-		AtimeNsec: opts.Stat.Atime.Nsec,
-		MtimeNsec: opts.Stat.Mtime.Nsec,
-		CtimeNsec: opts.Stat.Ctime.Nsec,
-		Mode:      uint32(fileType | opts.Stat.Mode),
-		UID:       opts.Stat.UID,
-		GID:       opts.Stat.GID,
-	}
-	req, err := conn.NewRequest(creds, uint32(task.ThreadID()), i.nodeID, linux.FUSE_SETATTR, &in)
-	if err != nil {
-		return err
-	}
-
-	res, err := conn.Call(task, req)
-	if err != nil {
-		return err
-	}
-	if err := res.Error(); err != nil {
-		return err
-	}
-	out := linux.FUSEGetAttrOut{}
-	if err := res.UnmarshalPayload(&out); err != nil {
-		return err
-	}
-
-	// Set the metadata of kernfs.InodeAttrs.
-	if err := i.SetInodeStat(ctx, fs, creds, vfs.SetStatOptions{
-		Stat: statFromFUSEAttr(out.Attr, linux.STATX_ALL, i.fs.devMinor),
-	}); err != nil {
-		return err
-	}
-
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/fuse/connection_control.go b/pkg/sentry/fsimpl/fuse/init.go
index a63c66e7c..779c2bd3f 100644
--- a/pkg/sentry/fsimpl/fuse/connection_control.go
+++ b/pkg/sentry/fsimpl/fuse/init.go
@@ -15,11 +15,7 @@
 package fuse
 
 import (
-	"sync/atomic"
-	"syscall"
-
 	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 )
 
@@ -33,10 +29,9 @@ const (
 	// Follow the same behavior as unix fuse implementation.
 	fuseMaxTimeGranNs = 1000000000
 
-	// Minimum value for MaxWrite and MaxRead.
+	// Minimum value for MaxWrite.
 	// Follow the same behavior as unix fuse implementation.
 	fuseMinMaxWrite = 4096
-	fuseMinMaxRead  = 4096
 
 	// Temporary default value for max readahead, 128kb.
 	fuseDefaultMaxReadahead = 131072
@@ -54,26 +49,6 @@ var (
 	MaxUserCongestionThreshold uint16 = fuseDefaultCongestionThreshold
 )
 
-// SetInitialized atomically sets the connection as initialized.
-func (conn *connection) SetInitialized() {
-	// Unblock the requests sent before INIT.
-	close(conn.initializedChan)
-
-	// Close the channel first to avoid the non-atomic situation
-	// where conn.initialized is true but there are
-	// tasks being blocked on the channel.
-	// And it prevents the newer tasks from gaining
-	// unnecessary higher chance to be issued before the blocked one.
-
-	atomic.StoreInt32(&(conn.initialized), int32(1))
-}
-
-// IsInitialized atomically check if the connection is initialized.
-// pairs with SetInitialized().
-func (conn *connection) Initialized() bool {
-	return atomic.LoadInt32(&(conn.initialized)) != 0
-}
-
 // InitSend sends a FUSE_INIT request.
 func (conn *connection) InitSend(creds *auth.Credentials, pid uint32) error {
 	in := linux.FUSEInitIn{
@@ -100,24 +75,24 @@ func (conn *connection) InitRecv(res *Response, hasSysAdminCap bool) error {
 		return err
 	}
 
-	initRes := fuseInitRes{initLen: res.DataLen()}
-	if err := res.UnmarshalPayload(&initRes); err != nil {
+	var out linux.FUSEInitOut
+	if err := res.UnmarshalPayload(&out); err != nil {
 		return err
 	}
 
-	return conn.initProcessReply(&initRes.initOut, hasSysAdminCap)
+	return conn.initProcessReply(&out, hasSysAdminCap)
 }
 
 // Process the FUSE_INIT reply from the FUSE server.
-// It tries to acquire the conn.asyncMu lock if minor version is newer than 13.
 func (conn *connection) initProcessReply(out *linux.FUSEInitOut, hasSysAdminCap bool) error {
-	// No matter error or not, always set initialzied.
-	// to unblock the blocked requests.
-	defer conn.SetInitialized()
-
 	// No support for old major fuse versions.
 	if out.Major != linux.FUSE_KERNEL_VERSION {
 		conn.connInitError = true
+
+		// Set the connection as initialized and unblock the blocked requests
+		// (i.e. return error for them).
+		conn.SetInitialized()
+
 		return nil
 	}
 
@@ -125,14 +100,29 @@ func (conn *connection) initProcessReply(out *linux.FUSEInitOut, hasSysAdminCap
 	conn.connInitSuccess = true
 	conn.minor = out.Minor
 
-	// No support for negotiating MaxWrite before minor version 5.
-	if out.Minor >= 5 {
-		conn.maxWrite = out.MaxWrite
-	} else {
-		conn.maxWrite = fuseMinMaxWrite
-	}
-	if conn.maxWrite < fuseMinMaxWrite {
-		conn.maxWrite = fuseMinMaxWrite
+	// No support for limits before minor version 13.
+	if out.Minor >= 13 {
+		conn.bgLock.Lock()
+
+		if out.MaxBackground > 0 {
+			conn.maxBackground = out.MaxBackground
+
+			if !hasSysAdminCap &&
+				conn.maxBackground > MaxUserBackgroundRequest {
+				conn.maxBackground = MaxUserBackgroundRequest
+			}
+		}
+
+		if out.CongestionThreshold > 0 {
+			conn.congestionThreshold = out.CongestionThreshold
+
+			if !hasSysAdminCap &&
+				conn.congestionThreshold > MaxUserCongestionThreshold {
+				conn.congestionThreshold = MaxUserCongestionThreshold
+			}
+		}
+
+		conn.bgLock.Unlock()
 	}
 
 	// No support for the following flags before minor version 6.
@@ -141,6 +131,8 @@ func (conn *connection) initProcessReply(out *linux.FUSEInitOut, hasSysAdminCap
 		conn.bigWrites = out.Flags&linux.FUSE_BIG_WRITES != 0
 		conn.dontMask = out.Flags&linux.FUSE_DONT_MASK != 0
 		conn.writebackCache = out.Flags&linux.FUSE_WRITEBACK_CACHE != 0
+		conn.cacheSymlinks = out.Flags&linux.FUSE_CACHE_SYMLINKS != 0
+		conn.abortErr = out.Flags&linux.FUSE_ABORT_ERROR != 0
 
 		// TODO(gvisor.dev/issue/3195): figure out how to use TimeGran (0 < TimeGran <= fuseMaxTimeGranNs).
 
@@ -156,90 +148,19 @@ func (conn *connection) initProcessReply(out *linux.FUSEInitOut, hasSysAdminCap
 		}
 	}
 
-	// No support for limits before minor version 13.
-	if out.Minor >= 13 {
-		conn.asyncMu.Lock()
-
-		if out.MaxBackground > 0 {
-			conn.asyncNumMax = out.MaxBackground
-
-			if !hasSysAdminCap &&
-				conn.asyncNumMax > MaxUserBackgroundRequest {
-				conn.asyncNumMax = MaxUserBackgroundRequest
-			}
-		}
-
-		if out.CongestionThreshold > 0 {
-			conn.asyncCongestionThreshold = out.CongestionThreshold
-
-			if !hasSysAdminCap &&
-				conn.asyncCongestionThreshold > MaxUserCongestionThreshold {
-				conn.asyncCongestionThreshold = MaxUserCongestionThreshold
-			}
-		}
-
-		conn.asyncMu.Unlock()
-	}
-
-	return nil
-}
-
-// Abort this FUSE connection.
-// It tries to acquire conn.fd.mu, conn.lock, conn.bgLock in order.
-// All possible requests waiting or blocking will be aborted.
-func (conn *connection) Abort(ctx context.Context) {
-	conn.fd.mu.Lock()
-	conn.mu.Lock()
-	conn.asyncMu.Lock()
-
-	if !conn.connected {
-		conn.asyncMu.Unlock()
-		conn.mu.Unlock()
-		conn.fd.mu.Unlock()
-		return
-	}
-
-	conn.connected = false
-
-	// Empty the `fd.queue` that holds the requests
-	// not yet read by the FUSE daemon yet.
-	// These are a subset of the requests in `fuse.completion` map.
-	for !conn.fd.queue.Empty() {
-		req := conn.fd.queue.Front()
-		conn.fd.queue.Remove(req)
-	}
-
-	var terminate []linux.FUSEOpID
-
-	// 2. Collect the requests have not been sent to FUSE daemon,
-	// or have not received a reply.
-	for unique := range conn.fd.completions {
-		terminate = append(terminate, unique)
-	}
-
-	// Release all locks to avoid deadlock.
-	conn.asyncMu.Unlock()
-	conn.mu.Unlock()
-	conn.fd.mu.Unlock()
-
-	// 1. The requets blocked before initialization.
-	// Will reach call() `connected` check and return.
-	if !conn.Initialized() {
-		conn.SetInitialized()
+	// No support for negotiating MaxWrite before minor version 5.
+	if out.Minor >= 5 {
+		conn.maxWrite = out.MaxWrite
+	} else {
+		conn.maxWrite = fuseMinMaxWrite
 	}
-
-	// 2. Terminate the requests collected above.
-	// Set ECONNABORTED error.
-	// sendError() will remove them from `fd.completion` map.
-	// Will enter the path of a normally received error.
-	for _, toTerminate := range terminate {
-		conn.fd.sendError(ctx, -int32(syscall.ECONNABORTED), toTerminate)
+	if conn.maxWrite < fuseMinMaxWrite {
+		conn.maxWrite = fuseMinMaxWrite
 	}
 
-	// 3. The requests not yet written to FUSE device.
-	// Early terminate.
-	// Will reach callFutureLocked() `connected` check and return.
-	close(conn.fd.fullQueueCh)
+	// Set connection as initialized and unblock the requests
+	// issued before init.
+	conn.SetInitialized()
 
-	// TODO(gvisor.dev/issue/3528): Forget all pending forget reqs.
+	return nil
 }
diff --git a/pkg/sentry/fsimpl/fuse/inode_refs.go b/pkg/sentry/fsimpl/fuse/inode_refs.go
index 5d1de6067..6b9456e1d 100644
--- a/pkg/sentry/fsimpl/fuse/inode_refs.go
+++ b/pkg/sentry/fsimpl/fuse/inode_refs.go
@@ -1,10 +1,10 @@
 package fuse
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/fuse/read_write.go b/pkg/sentry/fsimpl/fuse/read_write.go
deleted file mode 100644
index 625d1547f..000000000
--- a/pkg/sentry/fsimpl/fuse/read_write.go
+++ /dev/null
@@ -1,242 +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 fuse
-
-import (
-	"io"
-	"sync/atomic"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/log"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/usermem"
-)
-
-// ReadInPages sends FUSE_READ requests for the size after round it up to
-// a multiple of page size, blocks on it for reply, processes the reply
-// and returns the payload (or joined payloads) as a byte slice.
-// This is used for the general purpose reading.
-// We do not support direct IO (which read the exact number of bytes)
-// at this moment.
-func (fs *filesystem) ReadInPages(ctx context.Context, fd *regularFileFD, off uint64, size uint32) ([][]byte, uint32, error) {
-	attributeVersion := atomic.LoadUint64(&fs.conn.attributeVersion)
-
-	t := kernel.TaskFromContext(ctx)
-	if t == nil {
-		log.Warningf("fusefs.Read: couldn't get kernel task from context")
-		return nil, 0, syserror.EINVAL
-	}
-
-	// Round up to a multiple of page size.
-	readSize, _ := usermem.PageRoundUp(uint64(size))
-
-	// One request cannnot exceed either maxRead or maxPages.
-	maxPages := fs.conn.maxRead >> usermem.PageShift
-	if maxPages > uint32(fs.conn.maxPages) {
-		maxPages = uint32(fs.conn.maxPages)
-	}
-
-	var outs [][]byte
-	var sizeRead uint32
-
-	// readSize is a multiple of usermem.PageSize.
-	// Always request bytes as a multiple of pages.
-	pagesRead, pagesToRead := uint32(0), uint32(readSize>>usermem.PageShift)
-
-	// Reuse the same struct for unmarshalling to avoid unnecessary memory allocation.
-	in := linux.FUSEReadIn{
-		Fh:        fd.Fh,
-		LockOwner: 0, // TODO(gvisor.dev/issue/3245): file lock
-		ReadFlags: 0, // TODO(gvisor.dev/issue/3245): |= linux.FUSE_READ_LOCKOWNER
-		Flags:     fd.statusFlags(),
-	}
-
-	// This loop is intended for fragmented read where the bytes to read is
-	// larger than either the maxPages or maxRead.
-	// For the majority of reads with normal size, this loop should only
-	// execute once.
-	for pagesRead < pagesToRead {
-		pagesCanRead := pagesToRead - pagesRead
-		if pagesCanRead > maxPages {
-			pagesCanRead = maxPages
-		}
-
-		in.Offset = off + (uint64(pagesRead) << usermem.PageShift)
-		in.Size = pagesCanRead << usermem.PageShift
-
-		req, err := fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(t.ThreadID()), fd.inode().nodeID, linux.FUSE_READ, &in)
-		if err != nil {
-			return nil, 0, err
-		}
-
-		// TODO(gvisor.dev/issue/3247): support async read.
-
-		res, err := fs.conn.Call(t, req)
-		if err != nil {
-			return nil, 0, err
-		}
-		if err := res.Error(); err != nil {
-			return nil, 0, err
-		}
-
-		// Not enough bytes in response,
-		// either we reached EOF,
-		// or the FUSE server sends back a response
-		// that cannot even fit the hdr.
-		if len(res.data) <= res.hdr.SizeBytes() {
-			// We treat both case as EOF here for now
-			// since there is no reliable way to detect
-			// the over-short hdr case.
-			break
-		}
-
-		// Directly using the slice to avoid extra copy.
-		out := res.data[res.hdr.SizeBytes():]
-
-		outs = append(outs, out)
-		sizeRead += uint32(len(out))
-
-		pagesRead += pagesCanRead
-	}
-
-	defer fs.ReadCallback(ctx, fd, off, size, sizeRead, attributeVersion)
-
-	// No bytes returned: offset >= EOF.
-	if len(outs) == 0 {
-		return nil, 0, io.EOF
-	}
-
-	return outs, sizeRead, nil
-}
-
-// ReadCallback updates several information after receiving a read response.
-// Due to readahead, sizeRead can be larger than size.
-func (fs *filesystem) ReadCallback(ctx context.Context, fd *regularFileFD, off uint64, size uint32, sizeRead uint32, attributeVersion uint64) {
-	// TODO(gvisor.dev/issue/3247): support async read.
-	// If this is called by an async read, correctly process it.
-	// May need to update the signature.
-
-	i := fd.inode()
-	// TODO(gvisor.dev/issue/1193): Invalidate or update atime.
-
-	// Reached EOF.
-	if sizeRead < size {
-		// TODO(gvisor.dev/issue/3630): If we have writeback cache, then we need to fill this hole.
-		// Might need to update the buf to be returned from the Read().
-
-		// Update existing size.
-		newSize := off + uint64(sizeRead)
-		fs.conn.mu.Lock()
-		if attributeVersion == i.attributeVersion && newSize < atomic.LoadUint64(&i.size) {
-			fs.conn.attributeVersion++
-			i.attributeVersion = i.fs.conn.attributeVersion
-			atomic.StoreUint64(&i.size, newSize)
-		}
-		fs.conn.mu.Unlock()
-	}
-}
-
-// Write sends FUSE_WRITE requests and return the bytes
-// written according to the response.
-//
-// Preconditions: len(data) == size.
-func (fs *filesystem) Write(ctx context.Context, fd *regularFileFD, off uint64, size uint32, data []byte) (uint32, error) {
-	t := kernel.TaskFromContext(ctx)
-	if t == nil {
-		log.Warningf("fusefs.Read: couldn't get kernel task from context")
-		return 0, syserror.EINVAL
-	}
-
-	// One request cannnot exceed either maxWrite or maxPages.
-	maxWrite := uint32(fs.conn.maxPages) << usermem.PageShift
-	if maxWrite > fs.conn.maxWrite {
-		maxWrite = fs.conn.maxWrite
-	}
-
-	// Reuse the same struct for unmarshalling to avoid unnecessary memory allocation.
-	in := linux.FUSEWriteIn{
-		Fh: fd.Fh,
-		// TODO(gvisor.dev/issue/3245): file lock
-		LockOwner: 0,
-		// TODO(gvisor.dev/issue/3245): |= linux.FUSE_READ_LOCKOWNER
-		// TODO(gvisor.dev/issue/3237): |= linux.FUSE_WRITE_CACHE (not added yet)
-		WriteFlags: 0,
-		Flags:      fd.statusFlags(),
-	}
-
-	var written uint32
-
-	// This loop is intended for fragmented write where the bytes to write is
-	// larger than either the maxWrite or maxPages or when bigWrites is false.
-	// Unless a small value for max_write is explicitly used, this loop
-	// is expected to execute only once for the majority of the writes.
-	for written < size {
-		toWrite := size - written
-
-		// Limit the write size to one page.
-		// Note that the bigWrites flag is obsolete,
-		// latest libfuse always sets it on.
-		if !fs.conn.bigWrites && toWrite > usermem.PageSize {
-			toWrite = usermem.PageSize
-		}
-
-		// Limit the write size to maxWrite.
-		if toWrite > maxWrite {
-			toWrite = maxWrite
-		}
-
-		in.Offset = off + uint64(written)
-		in.Size = toWrite
-
-		req, err := fs.conn.NewRequest(auth.CredentialsFromContext(ctx), uint32(t.ThreadID()), fd.inode().nodeID, linux.FUSE_WRITE, &in)
-		if err != nil {
-			return 0, err
-		}
-
-		req.payload = data[written : written+toWrite]
-
-		// TODO(gvisor.dev/issue/3247): support async write.
-
-		res, err := fs.conn.Call(t, req)
-		if err != nil {
-			return 0, err
-		}
-		if err := res.Error(); err != nil {
-			return 0, err
-		}
-
-		out := linux.FUSEWriteOut{}
-		if err := res.UnmarshalPayload(&out); err != nil {
-			return 0, err
-		}
-
-		// Write more than requested? EIO.
-		if out.Size > toWrite {
-			return 0, syserror.EIO
-		}
-
-		written += out.Size
-
-		// Break if short write. Not necessarily an error.
-		if out.Size != toWrite {
-			break
-		}
-	}
-
-	return written, nil
-}
diff --git a/pkg/sentry/fsimpl/fuse/regular_file.go b/pkg/sentry/fsimpl/fuse/regular_file.go
deleted file mode 100644
index 5bdd096c3..000000000
--- a/pkg/sentry/fsimpl/fuse/regular_file.go
+++ /dev/null
@@ -1,230 +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 fuse
-
-import (
-	"io"
-	"math"
-	"sync"
-	"sync/atomic"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/sentry/vfs"
-	"gvisor.dev/gvisor/pkg/syserror"
-	"gvisor.dev/gvisor/pkg/usermem"
-)
-
-type regularFileFD struct {
-	fileDescription
-
-	// off is the file offset.
-	off int64
-	// offMu protects off.
-	offMu sync.Mutex
-}
-
-// PRead implements vfs.FileDescriptionImpl.PRead.
-func (fd *regularFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
-	if offset < 0 {
-		return 0, syserror.EINVAL
-	}
-
-	// Check that flags are supported.
-	//
-	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
-	if opts.Flags&^linux.RWF_HIPRI != 0 {
-		return 0, syserror.EOPNOTSUPP
-	}
-
-	size := dst.NumBytes()
-	if size == 0 {
-		// Early return if count is 0.
-		return 0, nil
-	} else if size > math.MaxUint32 {
-		// FUSE only supports uint32 for size.
-		// Overflow.
-		return 0, syserror.EINVAL
-	}
-
-	// TODO(gvisor.dev/issue/3678): Add direct IO support.
-
-	inode := fd.inode()
-
-	// Reading beyond EOF, update file size if outdated.
-	if uint64(offset+size) > atomic.LoadUint64(&inode.size) {
-		if err := inode.reviseAttr(ctx, linux.FUSE_GETATTR_FH, fd.Fh); err != nil {
-			return 0, err
-		}
-		// If the offset after update is still too large, return error.
-		if uint64(offset) >= atomic.LoadUint64(&inode.size) {
-			return 0, io.EOF
-		}
-	}
-
-	// Truncate the read with updated file size.
-	fileSize := atomic.LoadUint64(&inode.size)
-	if uint64(offset+size) > fileSize {
-		size = int64(fileSize) - offset
-	}
-
-	buffers, n, err := inode.fs.ReadInPages(ctx, fd, uint64(offset), uint32(size))
-	if err != nil {
-		return 0, err
-	}
-
-	// TODO(gvisor.dev/issue/3237): support indirect IO (e.g. caching),
-	// store the bytes that were read ahead.
-
-	// Update the number of bytes to copy for short read.
-	if n < uint32(size) {
-		size = int64(n)
-	}
-
-	// Copy the bytes read to the dst.
-	// This loop is intended for fragmented reads.
-	// For the majority of reads, this loop only execute once.
-	var copied int64
-	for _, buffer := range buffers {
-		toCopy := int64(len(buffer))
-		if copied+toCopy > size {
-			toCopy = size - copied
-		}
-		cp, err := dst.DropFirst64(copied).CopyOut(ctx, buffer[:toCopy])
-		if err != nil {
-			return 0, err
-		}
-		if int64(cp) != toCopy {
-			return 0, syserror.EIO
-		}
-		copied += toCopy
-	}
-
-	return copied, nil
-}
-
-// Read implements vfs.FileDescriptionImpl.Read.
-func (fd *regularFileFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
-	fd.offMu.Lock()
-	n, err := fd.PRead(ctx, dst, fd.off, opts)
-	fd.off += n
-	fd.offMu.Unlock()
-	return n, err
-}
-
-// PWrite implements vfs.FileDescriptionImpl.PWrite.
-func (fd *regularFileFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
-	n, _, err := fd.pwrite(ctx, src, offset, opts)
-	return n, err
-}
-
-// Write implements vfs.FileDescriptionImpl.Write.
-func (fd *regularFileFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
-	fd.offMu.Lock()
-	n, off, err := fd.pwrite(ctx, src, fd.off, opts)
-	fd.off = off
-	fd.offMu.Unlock()
-	return n, err
-}
-
-// pwrite returns the number of bytes written, final offset and error. The
-// final offset should be ignored by PWrite.
-func (fd *regularFileFD) pwrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (written, finalOff int64, err error) {
-	if offset < 0 {
-		return 0, offset, syserror.EINVAL
-	}
-
-	// Check that flags are supported.
-	//
-	// TODO(gvisor.dev/issue/2601): Support select preadv2 flags.
-	if opts.Flags&^linux.RWF_HIPRI != 0 {
-		return 0, offset, syserror.EOPNOTSUPP
-	}
-
-	inode := fd.inode()
-	inode.metadataMu.Lock()
-	defer inode.metadataMu.Unlock()
-
-	// If the file is opened with O_APPEND, update offset to file size.
-	// Note: since our Open() implements the interface of kernfs,
-	// and kernfs currently does not support O_APPEND, this will never
-	// be true before we switch out from kernfs.
-	if fd.vfsfd.StatusFlags()&linux.O_APPEND != 0 {
-		// Locking inode.metadataMu is sufficient for reading size
-		offset = int64(inode.size)
-	}
-
-	srclen := src.NumBytes()
-
-	if srclen > math.MaxUint32 {
-		// FUSE only supports uint32 for size.
-		// Overflow.
-		return 0, offset, syserror.EINVAL
-	}
-	if end := offset + srclen; end < offset {
-		// Overflow.
-		return 0, offset, syserror.EINVAL
-	}
-
-	srclen, err = vfs.CheckLimit(ctx, offset, srclen)
-	if err != nil {
-		return 0, offset, err
-	}
-
-	if srclen == 0 {
-		// Return before causing any side effects.
-		return 0, offset, nil
-	}
-
-	src = src.TakeFirst64(srclen)
-
-	// TODO(gvisor.dev/issue/3237): Add cache support:
-	// buffer cache. Ideally we write from src to our buffer cache first.
-	// The slice passed to fs.Write() should be a slice from buffer cache.
-	data := make([]byte, srclen)
-	// Reason for making a copy here: connection.Call() blocks on kerneltask,
-	// which in turn acquires mm.activeMu lock. Functions like CopyInTo() will
-	// attemp to acquire the mm.activeMu lock as well -> deadlock.
-	// We must finish reading from the userspace memory before
-	// t.Block() deactivates it.
-	cp, err := src.CopyIn(ctx, data)
-	if err != nil {
-		return 0, offset, err
-	}
-	if int64(cp) != srclen {
-		return 0, offset, syserror.EIO
-	}
-
-	n, err := fd.inode().fs.Write(ctx, fd, uint64(offset), uint32(srclen), data)
-	if err != nil {
-		return 0, offset, err
-	}
-
-	if n == 0 {
-		// We have checked srclen != 0 previously.
-		// If err == nil, then it's a short write and we return EIO.
-		return 0, offset, syserror.EIO
-	}
-
-	written = int64(n)
-	finalOff = offset + written
-
-	if finalOff > int64(inode.size) {
-		atomic.StoreUint64(&inode.size, uint64(finalOff))
-		atomic.AddUint64(&inode.fs.conn.attributeVersion, 1)
-	}
-
-	return
-}
diff --git a/pkg/sentry/fsimpl/fuse/request_response.go b/pkg/sentry/fsimpl/fuse/request_response.go
deleted file mode 100644
index 70db50f38..000000000
--- a/pkg/sentry/fsimpl/fuse/request_response.go
+++ /dev/null
@@ -1,229 +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 fuse
-
-import (
-	"fmt"
-	"syscall"
-
-	"gvisor.dev/gvisor/pkg/abi/linux"
-	"gvisor.dev/gvisor/pkg/sentry/kernel"
-	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
-	"gvisor.dev/gvisor/pkg/usermem"
-	"gvisor.dev/gvisor/tools/go_marshal/marshal"
-)
-
-// fuseInitRes is a variable-length wrapper of linux.FUSEInitOut. The FUSE
-// server may implement an older version of FUSE protocol, which contains a
-// linux.FUSEInitOut with less attributes.
-//
-// Dynamically-sized objects cannot be marshalled.
-type fuseInitRes struct {
-	marshal.StubMarshallable
-
-	// initOut contains the response from the FUSE server.
-	initOut linux.FUSEInitOut
-
-	// initLen is the total length of bytes of the response.
-	initLen uint32
-}
-
-// UnmarshalBytes deserializes src to the initOut attribute in a fuseInitRes.
-func (r *fuseInitRes) UnmarshalBytes(src []byte) {
-	out := &r.initOut
-
-	// Introduced before FUSE kernel version 7.13.
-	out.Major = uint32(usermem.ByteOrder.Uint32(src[:4]))
-	src = src[4:]
-	out.Minor = uint32(usermem.ByteOrder.Uint32(src[:4]))
-	src = src[4:]
-	out.MaxReadahead = uint32(usermem.ByteOrder.Uint32(src[:4]))
-	src = src[4:]
-	out.Flags = uint32(usermem.ByteOrder.Uint32(src[:4]))
-	src = src[4:]
-	out.MaxBackground = uint16(usermem.ByteOrder.Uint16(src[:2]))
-	src = src[2:]
-	out.CongestionThreshold = uint16(usermem.ByteOrder.Uint16(src[:2]))
-	src = src[2:]
-	out.MaxWrite = uint32(usermem.ByteOrder.Uint32(src[:4]))
-	src = src[4:]
-
-	// Introduced in FUSE kernel version 7.23.
-	if len(src) >= 4 {
-		out.TimeGran = uint32(usermem.ByteOrder.Uint32(src[:4]))
-		src = src[4:]
-	}
-	// Introduced in FUSE kernel version 7.28.
-	if len(src) >= 2 {
-		out.MaxPages = uint16(usermem.ByteOrder.Uint16(src[:2]))
-		src = src[2:]
-	}
-}
-
-// SizeBytes is the size of the payload of the FUSE_INIT response.
-func (r *fuseInitRes) SizeBytes() int {
-	return int(r.initLen)
-}
-
-// Ordinary requests have even IDs, while interrupts IDs are odd.
-// Used to increment the unique ID for each FUSE request.
-var reqIDStep uint64 = 2
-
-// Request represents a FUSE operation request that hasn't been sent to the
-// server yet.
-//
-// +stateify savable
-type Request struct {
-	requestEntry
-
-	id   linux.FUSEOpID
-	hdr  *linux.FUSEHeaderIn
-	data []byte
-
-	// payload for this request: extra bytes to write after
-	// the data slice. Used by FUSE_WRITE.
-	payload []byte
-
-	// If this request is async.
-	async bool
-	// If we don't care its response.
-	// Manually set by the caller.
-	noReply bool
-}
-
-// NewRequest creates a new request that can be sent to the FUSE server.
-func (conn *connection) NewRequest(creds *auth.Credentials, pid uint32, ino uint64, opcode linux.FUSEOpcode, payload marshal.Marshallable) (*Request, error) {
-	conn.fd.mu.Lock()
-	defer conn.fd.mu.Unlock()
-	conn.fd.nextOpID += linux.FUSEOpID(reqIDStep)
-
-	hdrLen := (*linux.FUSEHeaderIn)(nil).SizeBytes()
-	hdr := linux.FUSEHeaderIn{
-		Len:    uint32(hdrLen + payload.SizeBytes()),
-		Opcode: opcode,
-		Unique: conn.fd.nextOpID,
-		NodeID: ino,
-		UID:    uint32(creds.EffectiveKUID),
-		GID:    uint32(creds.EffectiveKGID),
-		PID:    pid,
-	}
-
-	buf := make([]byte, hdr.Len)
-
-	// TODO(gVisor.dev/issue/3698): Use the unsafe version once go_marshal is safe to use again.
-	hdr.MarshalBytes(buf[:hdrLen])
-	payload.MarshalBytes(buf[hdrLen:])
-
-	return &Request{
-		id:   hdr.Unique,
-		hdr:  &hdr,
-		data: buf,
-	}, nil
-}
-
-// futureResponse represents an in-flight request, that may or may not have
-// completed yet. Convert it to a resolved Response by calling Resolve, but note
-// that this may block.
-//
-// +stateify savable
-type futureResponse struct {
-	opcode linux.FUSEOpcode
-	ch     chan struct{}
-	hdr    *linux.FUSEHeaderOut
-	data   []byte
-
-	// If this request is async.
-	async bool
-}
-
-// newFutureResponse creates a future response to a FUSE request.
-func newFutureResponse(req *Request) *futureResponse {
-	return &futureResponse{
-		opcode: req.hdr.Opcode,
-		ch:     make(chan struct{}),
-		async:  req.async,
-	}
-}
-
-// resolve blocks the task until the server responds to its corresponding request,
-// then returns a resolved response.
-func (f *futureResponse) resolve(t *kernel.Task) (*Response, error) {
-	// Return directly for async requests.
-	if f.async {
-		return nil, nil
-	}
-
-	if err := t.Block(f.ch); err != nil {
-		return nil, err
-	}
-
-	return f.getResponse(), nil
-}
-
-// getResponse creates a Response from the data the futureResponse has.
-func (f *futureResponse) getResponse() *Response {
-	return &Response{
-		opcode: f.opcode,
-		hdr:    *f.hdr,
-		data:   f.data,
-	}
-}
-
-// Response represents an actual response from the server, including the
-// response payload.
-//
-// +stateify savable
-type Response struct {
-	opcode linux.FUSEOpcode
-	hdr    linux.FUSEHeaderOut
-	data   []byte
-}
-
-// Error returns the error of the FUSE call.
-func (r *Response) Error() error {
-	errno := r.hdr.Error
-	if errno >= 0 {
-		return nil
-	}
-
-	sysErrNo := syscall.Errno(-errno)
-	return error(sysErrNo)
-}
-
-// DataLen returns the size of the response without the header.
-func (r *Response) DataLen() uint32 {
-	return r.hdr.Len - uint32(r.hdr.SizeBytes())
-}
-
-// UnmarshalPayload unmarshals the response data into m.
-func (r *Response) UnmarshalPayload(m marshal.Marshallable) error {
-	hdrLen := r.hdr.SizeBytes()
-	haveDataLen := r.hdr.Len - uint32(hdrLen)
-	wantDataLen := uint32(m.SizeBytes())
-
-	if haveDataLen < wantDataLen {
-		return fmt.Errorf("payload too small. Minimum data lenth required: %d,  but got data length %d", wantDataLen, haveDataLen)
-	}
-
-	// The response data is empty unless there is some payload. And so, doesn't
-	// need to be unmarshalled.
-	if r.data == nil {
-		return nil
-	}
-
-	// TODO(gVisor.dev/issue/3698): Use the unsafe version once go_marshal is safe to use again.
-	m.UnmarshalBytes(r.data[hdrLen:])
-	return nil
-}
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index fa4e19113..0e21c31a4 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -195,11 +195,7 @@ const (
 	// and consistent with Linux's semantics (in particular, it is not always
 	// possible for clients to set arbitrary atimes and mtimes depending on the
 	// remote filesystem implementation, and never possible for clients to set
-	// arbitrary ctimes.) If a dentry containing a client-defined atime or
-	// mtime is evicted from cache, client timestamps will be sent to the
-	// remote filesystem on a best-effort basis to attempt to ensure that
-	// timestamps will be preserved when another dentry representing the same
-	// file is instantiated.
+	// arbitrary ctimes.)
 	InteropModeExclusive InteropMode = iota
 
 	// InteropModeWritethrough is appropriate when there are read-only users of
@@ -1315,32 +1311,15 @@ func (d *dentry) destroyLocked(ctx context.Context) {
 	d.handleMu.Unlock()
 
 	if !d.file.isNil() {
-		valid := p9.SetAttrMask{}
-		attr := p9.SetAttr{}
-		if !d.isDeleted() {
-			// Write dirty timestamps back to the remote filesystem.
-			if atomic.LoadUint32(&d.atimeDirty) != 0 {
-				valid.ATime = true
-				valid.ATimeNotSystemTime = true
-				atime := atomic.LoadInt64(&d.atime)
-				attr.ATimeSeconds = uint64(atime / 1e9)
-				attr.ATimeNanoSeconds = uint64(atime % 1e9)
-			}
-			if atomic.LoadUint32(&d.mtimeDirty) != 0 {
-				valid.MTime = true
-				valid.MTimeNotSystemTime = true
-				mtime := atomic.LoadInt64(&d.mtime)
-				attr.MTimeSeconds = uint64(mtime / 1e9)
-				attr.MTimeNanoSeconds = uint64(mtime % 1e9)
-			}
-		}
-
-		// Check if attributes need to be changed before closing the file.
-		if valid.ATime || valid.MTime {
-			if err := d.file.setAttrClose(ctx, valid, attr); err != nil {
-				log.Warningf("gofer.dentry.destroyLocked: failed to close file with write dirty timestamps: %v", err)
-			}
-		} else if err := d.file.close(ctx); err != nil {
+		// Note that it's possible that d.atimeDirty or d.mtimeDirty are true,
+		// i.e. client and server timestamps may differ (because e.g. a client
+		// write was serviced by the page cache, and only written back to the
+		// remote file later). Ideally, we'd write client timestamps back to
+		// the remote filesystem so that timestamps for a new dentry
+		// instantiated for the same file would remain coherent. Unfortunately,
+		// this turns out to be too expensive in many cases, so for now we
+		// don't do this.
+		if err := d.file.close(ctx); err != nil {
 			log.Warningf("gofer.dentry.destroyLocked: failed to close file: %v", err)
 		}
 		d.file = p9file{}
diff --git a/pkg/sentry/fsimpl/host/connected_endpoint_refs.go b/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
index abf4a9082..babb3f664 100644
--- a/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
+++ b/pkg/sentry/fsimpl/host/connected_endpoint_refs.go
@@ -1,10 +1,10 @@
 package host
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/host/inode_refs.go b/pkg/sentry/fsimpl/host/inode_refs.go
index 75b9f49e2..17f90ce4a 100644
--- a/pkg/sentry/fsimpl/host/inode_refs.go
+++ b/pkg/sentry/fsimpl/host/inode_refs.go
@@ -1,10 +1,10 @@
 package host
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/host/socket_unsafe.go b/pkg/sentry/fsimpl/host/socket_unsafe.go
index 35ded24bc..c0bf45f08 100644
--- a/pkg/sentry/fsimpl/host/socket_unsafe.go
+++ b/pkg/sentry/fsimpl/host/socket_unsafe.go
@@ -63,10 +63,10 @@ func fdReadVec(fd int, bufs [][]byte, control []byte, peek bool, maxlen int64) (
 	controlTrunc = msg.Flags&syscall.MSG_CTRUNC == syscall.MSG_CTRUNC
 
 	if n > length {
-		return length, n, msg.Controllen, controlTrunc, err
+		return length, n, msg.Controllen, controlTrunc, nil
 	}
 
-	return n, n, msg.Controllen, controlTrunc, err
+	return n, n, msg.Controllen, controlTrunc, nil
 }
 
 // fdWriteVec sends from bufs to fd.
diff --git a/pkg/sentry/fsimpl/host/tty.go b/pkg/sentry/fsimpl/host/tty.go
index 7a9be4b97..97cefa350 100644
--- a/pkg/sentry/fsimpl/host/tty.go
+++ b/pkg/sentry/fsimpl/host/tty.go
@@ -17,6 +17,7 @@ package host
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
@@ -25,7 +26,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
-	"gvisor.dev/gvisor/tools/go_marshal/primitive"
 )
 
 // TTYFileDescription implements vfs.FileDescriptionImpl for a host file
diff --git a/pkg/sentry/fsimpl/kernfs/dentry_refs.go b/pkg/sentry/fsimpl/kernfs/dentry_refs.go
index b7125caee..79863b3bc 100644
--- a/pkg/sentry/fsimpl/kernfs/dentry_refs.go
+++ b/pkg/sentry/fsimpl/kernfs/dentry_refs.go
@@ -1,10 +1,10 @@
 package kernfs
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 49f6a0f1d..d7d3e8f48 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -140,7 +140,7 @@ func (fs *Filesystem) revalidateChildLocked(ctx context.Context, vfsObj *vfs.Vir
 		}
 		// Reference on childVFSD dropped by a corresponding Valid.
 		child = childVFSD.Impl().(*Dentry)
-		parent.InsertChildLocked(name, child)
+		parent.insertChildLocked(name, child)
 	}
 	return child, nil
 }
@@ -548,7 +548,7 @@ func (fs *Filesystem) ReadlinkAt(ctx context.Context, rp *vfs.ResolvingPath) (st
 	if !d.Impl().(*Dentry).isSymlink() {
 		return "", syserror.EINVAL
 	}
-	return inode.Readlink(ctx, rp.Mount())
+	return inode.Readlink(ctx)
 }
 
 // RenameAt implements vfs.FilesystemImpl.RenameAt.
@@ -657,10 +657,6 @@ func (fs *Filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, oldPa
 func (fs *Filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error {
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
-
-	// Store the name before walkExistingLocked as rp will be advanced past the
-	// name in the following call.
-	name := rp.Component()
 	vfsd, inode, err := fs.walkExistingLocked(ctx, rp)
 	fs.processDeferredDecRefsLocked(ctx)
 	if err != nil {
@@ -690,8 +686,7 @@ func (fs *Filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	if err := virtfs.PrepareDeleteDentry(mntns, vfsd); err != nil {
 		return err
 	}
-
-	if err := parentDentry.inode.RmDir(ctx, name, vfsd); err != nil {
+	if err := parentDentry.inode.RmDir(ctx, rp.Component(), vfsd); err != nil {
 		virtfs.AbortDeleteDentry(vfsd)
 		return err
 	}
@@ -770,10 +765,6 @@ func (fs *Filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, targ
 func (fs *Filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error {
 	fs.mu.Lock()
 	defer fs.mu.Unlock()
-
-	// Store the name before walkExistingLocked as rp will be advanced past the
-	// name in the following call.
-	name := rp.Component()
 	vfsd, _, err := fs.walkExistingLocked(ctx, rp)
 	fs.processDeferredDecRefsLocked(ctx)
 	if err != nil {
@@ -799,7 +790,7 @@ func (fs *Filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	if err := virtfs.PrepareDeleteDentry(mntns, vfsd); err != nil {
 		return err
 	}
-	if err := parentDentry.inode.Unlink(ctx, name, vfsd); err != nil {
+	if err := parentDentry.inode.Unlink(ctx, rp.Component(), vfsd); err != nil {
 		virtfs.AbortDeleteDentry(vfsd)
 		return err
 	}
diff --git a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
index ea4f679c2..c0b863ba4 100644
--- a/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
+++ b/pkg/sentry/fsimpl/kernfs/inode_impl_util.go
@@ -172,7 +172,7 @@ func (InodeNoDynamicLookup) Valid(ctx context.Context) bool {
 type InodeNotSymlink struct{}
 
 // Readlink implements Inode.Readlink.
-func (InodeNotSymlink) Readlink(context.Context, *vfs.Mount) (string, error) {
+func (InodeNotSymlink) Readlink(context.Context) (string, error) {
 	return "", syserror.EINVAL
 }
 
@@ -256,13 +256,6 @@ func (a *InodeAttrs) Stat(context.Context, *vfs.Filesystem, vfs.StatOptions) (li
 
 // SetStat implements Inode.SetStat.
 func (a *InodeAttrs) SetStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
-	return a.SetInodeStat(ctx, fs, creds, opts)
-}
-
-// SetInodeStat sets the corresponding attributes from opts to InodeAttrs.
-// This function can be used by other kernfs-based filesystem implementation to
-// sets the unexported attributes into kernfs.InodeAttrs.
-func (a *InodeAttrs) SetInodeStat(ctx context.Context, fs *vfs.Filesystem, creds *auth.Credentials, opts vfs.SetStatOptions) error {
 	if opts.Stat.Mask == 0 {
 		return nil
 	}
diff --git a/pkg/sentry/fsimpl/kernfs/kernfs.go b/pkg/sentry/fsimpl/kernfs/kernfs.go
index 163f26ceb..88fcd54aa 100644
--- a/pkg/sentry/fsimpl/kernfs/kernfs.go
+++ b/pkg/sentry/fsimpl/kernfs/kernfs.go
@@ -60,7 +60,6 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
-	"gvisor.dev/gvisor/pkg/syserror"
 )
 
 // Filesystem mostly implements vfs.FilesystemImpl for a generic in-memory
@@ -247,15 +246,15 @@ func (d *Dentry) OnZeroWatches(context.Context) {}
 // Precondition: d must represent a directory inode.
 func (d *Dentry) InsertChild(name string, child *Dentry) {
 	d.dirMu.Lock()
-	d.InsertChildLocked(name, child)
+	d.insertChildLocked(name, child)
 	d.dirMu.Unlock()
 }
 
-// InsertChildLocked is equivalent to InsertChild, with additional
+// insertChildLocked is equivalent to InsertChild, with additional
 // preconditions.
 //
 // Precondition: d.dirMu must be locked.
-func (d *Dentry) InsertChildLocked(name string, child *Dentry) {
+func (d *Dentry) insertChildLocked(name string, child *Dentry) {
 	if !d.isDir() {
 		panic(fmt.Sprintf("InsertChild called on non-directory Dentry: %+v.", d))
 	}
@@ -268,36 +267,6 @@ func (d *Dentry) InsertChildLocked(name string, child *Dentry) {
 	d.children[name] = child
 }
 
-// RemoveChild removes child from the vfs dentry cache. This does not update the
-// directory inode or modify the inode to be unlinked. So calling this on its own
-// isn't sufficient to remove a child from a directory.
-//
-// Precondition: d must represent a directory inode.
-func (d *Dentry) RemoveChild(name string, child *vfs.Dentry) error {
-	d.dirMu.Lock()
-	defer d.dirMu.Unlock()
-	return d.RemoveChildLocked(name, child)
-}
-
-// RemoveChildLocked is equivalent to RemoveChild, with additional
-// preconditions.
-//
-// Precondition: d.dirMu must be locked.
-func (d *Dentry) RemoveChildLocked(name string, child *vfs.Dentry) error {
-	if !d.isDir() {
-		panic(fmt.Sprintf("RemoveChild called on non-directory Dentry: %+v.", d))
-	}
-	c, ok := d.children[name]
-	if !ok {
-		return syserror.ENOENT
-	}
-	if &c.vfsd != child {
-		panic(fmt.Sprintf("Dentry hashed into inode doesn't match what vfs thinks! Child: %+v, vfs: %+v", c, child))
-	}
-	delete(d.children, name)
-	return nil
-}
-
 // Inode returns the dentry's inode.
 func (d *Dentry) Inode() Inode {
 	return d.inode
@@ -456,7 +425,7 @@ type inodeDynamicLookup interface {
 	Valid(ctx context.Context) bool
 
 	// IterDirents is used to iterate over dynamically created entries. It invokes
-	// cb on each entry in the directory represented by the Inode.
+	// cb on each entry in the directory represented by the FileDescription.
 	// 'offset' is the offset for the entire IterDirents call, which may include
 	// results from the caller (e.g. "." and ".."). 'relOffset' is the offset
 	// inside the entries returned by this IterDirents invocation. In other words,
@@ -468,7 +437,7 @@ type inodeDynamicLookup interface {
 type inodeSymlink interface {
 	// Readlink returns the target of a symbolic link. If an inode is not a
 	// symlink, the implementation should return EINVAL.
-	Readlink(ctx context.Context, mnt *vfs.Mount) (string, error)
+	Readlink(ctx context.Context) (string, error)
 
 	// Getlink returns the target of a symbolic link, as used by path
 	// resolution:
diff --git a/pkg/sentry/fsimpl/kernfs/static_directory_refs.go b/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
index 0ff013c97..478b04bdd 100644
--- a/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
+++ b/pkg/sentry/fsimpl/kernfs/static_directory_refs.go
@@ -1,10 +1,10 @@
 package kernfs
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/kernfs/symlink.go b/pkg/sentry/fsimpl/kernfs/symlink.go
index a9812fcef..64731a3e4 100644
--- a/pkg/sentry/fsimpl/kernfs/symlink.go
+++ b/pkg/sentry/fsimpl/kernfs/symlink.go
@@ -52,7 +52,7 @@ func (s *StaticSymlink) Init(creds *auth.Credentials, devMajor uint32, devMinor
 }
 
 // Readlink implements Inode.
-func (s *StaticSymlink) Readlink(_ context.Context, _ *vfs.Mount) (string, error) {
+func (s *StaticSymlink) Readlink(_ context.Context) (string, error) {
 	return s.target, nil
 }
 
diff --git a/pkg/sentry/fsimpl/overlay/copy_up.go b/pkg/sentry/fsimpl/overlay/copy_up.go
index c589b4746..360b77ef6 100644
--- a/pkg/sentry/fsimpl/overlay/copy_up.go
+++ b/pkg/sentry/fsimpl/overlay/copy_up.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
@@ -81,6 +82,8 @@ func (d *dentry) copyUpLocked(ctx context.Context) error {
 		Start: d.parent.upperVD,
 		Path:  fspath.Parse(d.name),
 	}
+	// Used during copy-up of memory-mapped regular files.
+	var mmapOpts *memmap.MMapOpts
 	cleanupUndoCopyUp := func() {
 		var err error
 		if ftype == linux.S_IFDIR {
@@ -136,6 +139,25 @@ func (d *dentry) copyUpLocked(ctx context.Context) error {
 				break
 			}
 		}
+		d.mapsMu.Lock()
+		defer d.mapsMu.Unlock()
+		if d.wrappedMappable != nil {
+			// We may have memory mappings of the file on the lower layer.
+			// Switch to mapping the file on the upper layer instead.
+			mmapOpts = &memmap.MMapOpts{
+				Perms:    usermem.ReadWrite,
+				MaxPerms: usermem.ReadWrite,
+			}
+			if err := newFD.ConfigureMMap(ctx, mmapOpts); err != nil {
+				cleanupUndoCopyUp()
+				return err
+			}
+			if mmapOpts.MappingIdentity != nil {
+				mmapOpts.MappingIdentity.DecRef(ctx)
+			}
+			// Don't actually switch Mappables until the end of copy-up; see
+			// below for why.
+		}
 		if err := newFD.SetStat(ctx, vfs.SetStatOptions{
 			Stat: linux.Statx{
 				Mask: linux.STATX_UID | linux.STATX_GID,
@@ -265,6 +287,62 @@ func (d *dentry) copyUpLocked(ctx context.Context) error {
 		atomic.StoreUint64(&d.ino, upperStat.Ino)
 	}
 
+	if mmapOpts != nil && mmapOpts.Mappable != nil {
+		// Note that if mmapOpts != nil, then d.mapsMu is locked for writing
+		// (from the S_IFREG path above).
+
+		// Propagate mappings of d to the new Mappable. Remember which mappings
+		// we added so we can remove them on failure.
+		upperMappable := mmapOpts.Mappable
+		allAdded := make(map[memmap.MappableRange]memmap.MappingsOfRange)
+		for seg := d.lowerMappings.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
+			added := make(memmap.MappingsOfRange)
+			for m := range seg.Value() {
+				if err := upperMappable.AddMapping(ctx, m.MappingSpace, m.AddrRange, seg.Start(), m.Writable); err != nil {
+					for m := range added {
+						upperMappable.RemoveMapping(ctx, m.MappingSpace, m.AddrRange, seg.Start(), m.Writable)
+					}
+					for mr, mappings := range allAdded {
+						for m := range mappings {
+							upperMappable.RemoveMapping(ctx, m.MappingSpace, m.AddrRange, mr.Start, m.Writable)
+						}
+					}
+					return err
+				}
+				added[m] = struct{}{}
+			}
+			allAdded[seg.Range()] = added
+		}
+
+		// Switch to the new Mappable. We do this at the end of copy-up
+		// because:
+		//
+		// - We need to switch Mappables (by changing d.wrappedMappable) before
+		// invalidating Translations from the old Mappable (to pick up
+		// Translations from the new one).
+		//
+		// - We need to lock d.dataMu while changing d.wrappedMappable, but
+		// must invalidate Translations with d.dataMu unlocked (due to lock
+		// ordering).
+		//
+		// - Consequently, once we unlock d.dataMu, other threads may
+		// immediately observe the new (copied-up) Mappable, which we want to
+		// delay until copy-up is guaranteed to succeed.
+		d.dataMu.Lock()
+		lowerMappable := d.wrappedMappable
+		d.wrappedMappable = upperMappable
+		d.dataMu.Unlock()
+		d.lowerMappings.InvalidateAll(memmap.InvalidateOpts{})
+
+		// Remove mappings from the old Mappable.
+		for seg := d.lowerMappings.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
+			for m := range seg.Value() {
+				lowerMappable.RemoveMapping(ctx, m.MappingSpace, m.AddrRange, seg.Start(), m.Writable)
+			}
+		}
+		d.lowerMappings.RemoveAll()
+	}
+
 	atomic.StoreUint32(&d.copiedUp, 1)
 	return nil
 }
diff --git a/pkg/sentry/fsimpl/overlay/non_directory.go b/pkg/sentry/fsimpl/overlay/non_directory.go
index 268b32537..74cfd3799 100644
--- a/pkg/sentry/fsimpl/overlay/non_directory.go
+++ b/pkg/sentry/fsimpl/overlay/non_directory.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
+	"gvisor.dev/gvisor/pkg/syserror"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -256,10 +257,105 @@ func (fd *nonDirectoryFD) Sync(ctx context.Context) error {
 
 // ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
 func (fd *nonDirectoryFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
-	wrappedFD, err := fd.getCurrentFD(ctx)
+	if err := fd.ensureMappable(ctx, opts); err != nil {
+		return err
+	}
+	return vfs.GenericConfigureMMap(&fd.vfsfd, fd.dentry(), opts)
+}
+
+// ensureMappable ensures that fd.dentry().wrappedMappable is not nil.
+func (fd *nonDirectoryFD) ensureMappable(ctx context.Context, opts *memmap.MMapOpts) error {
+	d := fd.dentry()
+
+	// Fast path if we already have a Mappable for the current top layer.
+	if atomic.LoadUint32(&d.isMappable) != 0 {
+		return nil
+	}
+
+	// Only permit mmap of regular files, since other file types may have
+	// unpredictable behavior when mmapped (e.g. /dev/zero).
+	if atomic.LoadUint32(&d.mode)&linux.S_IFMT != linux.S_IFREG {
+		return syserror.ENODEV
+	}
+
+	// Get a Mappable for the current top layer.
+	fd.mu.Lock()
+	defer fd.mu.Unlock()
+	d.copyMu.RLock()
+	defer d.copyMu.RUnlock()
+	if atomic.LoadUint32(&d.isMappable) != 0 {
+		return nil
+	}
+	wrappedFD, err := fd.currentFDLocked(ctx)
 	if err != nil {
 		return err
 	}
-	defer wrappedFD.DecRef(ctx)
-	return wrappedFD.ConfigureMMap(ctx, opts)
+	if err := wrappedFD.ConfigureMMap(ctx, opts); err != nil {
+		return err
+	}
+	if opts.MappingIdentity != nil {
+		opts.MappingIdentity.DecRef(ctx)
+		opts.MappingIdentity = nil
+	}
+	// Use this Mappable for all mappings of this layer (unless we raced with
+	// another call to ensureMappable).
+	d.mapsMu.Lock()
+	defer d.mapsMu.Unlock()
+	d.dataMu.Lock()
+	defer d.dataMu.Unlock()
+	if d.wrappedMappable == nil {
+		d.wrappedMappable = opts.Mappable
+		atomic.StoreUint32(&d.isMappable, 1)
+	}
+	return nil
+}
+
+// AddMapping implements memmap.Mappable.AddMapping.
+func (d *dentry) AddMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) error {
+	d.mapsMu.Lock()
+	defer d.mapsMu.Unlock()
+	if err := d.wrappedMappable.AddMapping(ctx, ms, ar, offset, writable); err != nil {
+		return err
+	}
+	if !d.isCopiedUp() {
+		d.lowerMappings.AddMapping(ms, ar, offset, writable)
+	}
+	return nil
+}
+
+// RemoveMapping implements memmap.Mappable.RemoveMapping.
+func (d *dentry) RemoveMapping(ctx context.Context, ms memmap.MappingSpace, ar usermem.AddrRange, offset uint64, writable bool) {
+	d.mapsMu.Lock()
+	defer d.mapsMu.Unlock()
+	d.wrappedMappable.RemoveMapping(ctx, ms, ar, offset, writable)
+	if !d.isCopiedUp() {
+		d.lowerMappings.RemoveMapping(ms, ar, offset, writable)
+	}
+}
+
+// CopyMapping implements memmap.Mappable.CopyMapping.
+func (d *dentry) CopyMapping(ctx context.Context, ms memmap.MappingSpace, srcAR, dstAR usermem.AddrRange, offset uint64, writable bool) error {
+	d.mapsMu.Lock()
+	defer d.mapsMu.Unlock()
+	if err := d.wrappedMappable.CopyMapping(ctx, ms, srcAR, dstAR, offset, writable); err != nil {
+		return err
+	}
+	if !d.isCopiedUp() {
+		d.lowerMappings.AddMapping(ms, dstAR, offset, writable)
+	}
+	return nil
+}
+
+// Translate implements memmap.Mappable.Translate.
+func (d *dentry) Translate(ctx context.Context, required, optional memmap.MappableRange, at usermem.AccessType) ([]memmap.Translation, error) {
+	d.dataMu.RLock()
+	defer d.dataMu.RUnlock()
+	return d.wrappedMappable.Translate(ctx, required, optional, at)
+}
+
+// InvalidateUnsavable implements memmap.Mappable.InvalidateUnsavable.
+func (d *dentry) InvalidateUnsavable(ctx context.Context) error {
+	d.mapsMu.Lock()
+	defer d.mapsMu.Unlock()
+	return d.wrappedMappable.InvalidateUnsavable(ctx)
 }
diff --git a/pkg/sentry/fsimpl/overlay/overlay.go b/pkg/sentry/fsimpl/overlay/overlay.go
index 9a8f7010e..b2efe5f80 100644
--- a/pkg/sentry/fsimpl/overlay/overlay.go
+++ b/pkg/sentry/fsimpl/overlay/overlay.go
@@ -22,6 +22,10 @@
 //   filesystem.renameMu
 //     dentry.dirMu
 //       dentry.copyMu
+//         *** "memmap.Mappable locks" below this point
+//         dentry.mapsMu
+//           *** "memmap.Mappable locks taken by Translate" below this point
+//           dentry.dataMu
 //
 // Locking dentry.dirMu in multiple dentries requires that parent dentries are
 // locked before child dentries, and that filesystem.renameMu is locked to
@@ -37,6 +41,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fspath"
 	fslock "gvisor.dev/gvisor/pkg/sentry/fs/lock"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -419,6 +424,35 @@ type dentry struct {
 	devMinor uint32
 	ino      uint64
 
+	// If this dentry represents a regular file, then:
+	//
+	// - mapsMu is used to synchronize between copy-up and memmap.Mappable
+	// methods on dentry preceding mm.MemoryManager.activeMu in the lock order.
+	//
+	// - dataMu is used to synchronize between copy-up and
+	// dentry.(memmap.Mappable).Translate.
+	//
+	// - lowerMappings tracks memory mappings of the file. lowerMappings is
+	// used to invalidate mappings of the lower layer when the file is copied
+	// up to ensure that they remain coherent with subsequent writes to the
+	// file. (Note that, as of this writing, Linux overlayfs does not do this;
+	// this feature is a gVisor extension.) lowerMappings is protected by
+	// mapsMu.
+	//
+	// - If this dentry is copied-up, then wrappedMappable is the Mappable
+	// obtained from a call to the current top layer's
+	// FileDescription.ConfigureMMap(). Once wrappedMappable becomes non-nil
+	// (from a call to nonDirectoryFD.ensureMappable()), it cannot become nil.
+	// wrappedMappable is protected by mapsMu and dataMu.
+	//
+	// - isMappable is non-zero iff wrappedMappable is non-nil. isMappable is
+	// accessed using atomic memory operations.
+	mapsMu          sync.Mutex
+	lowerMappings   memmap.MappingSet
+	dataMu          sync.RWMutex
+	wrappedMappable memmap.Mappable
+	isMappable      uint32
+
 	locks vfs.FileLocks
 }
 
diff --git a/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go b/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
index 454862d98..9431c1506 100644
--- a/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/fd_dir_inode_refs.go
@@ -1,10 +1,10 @@
 package proc
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go b/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
index d2169be5b..872b20eb0 100644
--- a/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/fd_info_dir_inode_refs.go
@@ -1,10 +1,10 @@
 package proc
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go b/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
index 9b50f632c..c6d9b3522 100644
--- a/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/subtasks_inode_refs.go
@@ -1,10 +1,10 @@
 package proc
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/proc/task_fds.go b/pkg/sentry/fsimpl/proc/task_fds.go
index 5374538c9..3f0d78461 100644
--- a/pkg/sentry/fsimpl/proc/task_fds.go
+++ b/pkg/sentry/fsimpl/proc/task_fds.go
@@ -209,7 +209,7 @@ func (fs *filesystem) newFDSymlink(task *kernel.Task, fd int32, ino uint64) *ker
 	return d
 }
 
-func (s *fdSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string, error) {
+func (s *fdSymlink) Readlink(ctx context.Context) (string, error) {
 	file, _ := getTaskFD(s.task, s.fd)
 	if file == nil {
 		return "", syserror.ENOENT
diff --git a/pkg/sentry/fsimpl/proc/task_files.go b/pkg/sentry/fsimpl/proc/task_files.go
index 4f7f9cb00..356036b9b 100644
--- a/pkg/sentry/fsimpl/proc/task_files.go
+++ b/pkg/sentry/fsimpl/proc/task_files.go
@@ -668,7 +668,7 @@ func (fs *filesystem) newExeSymlink(task *kernel.Task, ino uint64) *kernfs.Dentr
 }
 
 // Readlink implements kernfs.Inode.
-func (s *exeSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string, error) {
+func (s *exeSymlink) Readlink(ctx context.Context) (string, error) {
 	if !kernel.ContextCanTrace(ctx, s.task, false) {
 		return "", syserror.EACCES
 	}
@@ -808,11 +808,11 @@ func (fs *filesystem) newNamespaceSymlink(task *kernel.Task, ino uint64, ns stri
 }
 
 // Readlink implements Inode.
-func (s *namespaceSymlink) Readlink(ctx context.Context, mnt *vfs.Mount) (string, error) {
+func (s *namespaceSymlink) Readlink(ctx context.Context) (string, error) {
 	if err := checkTaskState(s.task); err != nil {
 		return "", err
 	}
-	return s.StaticSymlink.Readlink(ctx, mnt)
+	return s.StaticSymlink.Readlink(ctx)
 }
 
 // Getlink implements Inode.Getlink.
diff --git a/pkg/sentry/fsimpl/proc/task_inode_refs.go b/pkg/sentry/fsimpl/proc/task_inode_refs.go
index c29272f9b..714488450 100644
--- a/pkg/sentry/fsimpl/proc/task_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/task_inode_refs.go
@@ -1,10 +1,10 @@
 package proc
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/proc/tasks_files.go b/pkg/sentry/fsimpl/proc/tasks_files.go
index 68c541046..8c41729e4 100644
--- a/pkg/sentry/fsimpl/proc/tasks_files.go
+++ b/pkg/sentry/fsimpl/proc/tasks_files.go
@@ -51,7 +51,7 @@ func (fs *filesystem) newSelfSymlink(creds *auth.Credentials, ino uint64, pidns
 	return d
 }
 
-func (s *selfSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string, error) {
+func (s *selfSymlink) Readlink(ctx context.Context) (string, error) {
 	t := kernel.TaskFromContext(ctx)
 	if t == nil {
 		// Who is reading this link?
@@ -64,8 +64,8 @@ func (s *selfSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string, error
 	return strconv.FormatUint(uint64(tgid), 10), nil
 }
 
-func (s *selfSymlink) Getlink(ctx context.Context, mnt *vfs.Mount) (vfs.VirtualDentry, string, error) {
-	target, err := s.Readlink(ctx, mnt)
+func (s *selfSymlink) Getlink(ctx context.Context, _ *vfs.Mount) (vfs.VirtualDentry, string, error) {
+	target, err := s.Readlink(ctx)
 	return vfs.VirtualDentry{}, target, err
 }
 
@@ -94,7 +94,7 @@ func (fs *filesystem) newThreadSelfSymlink(creds *auth.Credentials, ino uint64,
 	return d
 }
 
-func (s *threadSelfSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string, error) {
+func (s *threadSelfSymlink) Readlink(ctx context.Context) (string, error) {
 	t := kernel.TaskFromContext(ctx)
 	if t == nil {
 		// Who is reading this link?
@@ -108,8 +108,8 @@ func (s *threadSelfSymlink) Readlink(ctx context.Context, _ *vfs.Mount) (string,
 	return fmt.Sprintf("%d/task/%d", tgid, tid), nil
 }
 
-func (s *threadSelfSymlink) Getlink(ctx context.Context, mnt *vfs.Mount) (vfs.VirtualDentry, string, error) {
-	target, err := s.Readlink(ctx, mnt)
+func (s *threadSelfSymlink) Getlink(ctx context.Context, _ *vfs.Mount) (vfs.VirtualDentry, string, error) {
+	target, err := s.Readlink(ctx)
 	return vfs.VirtualDentry{}, target, err
 }
 
diff --git a/pkg/sentry/fsimpl/proc/tasks_inode_refs.go b/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
index 7e0b70f6c..22d9cc488 100644
--- a/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
+++ b/pkg/sentry/fsimpl/proc/tasks_inode_refs.go
@@ -1,10 +1,10 @@
 package proc
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/sys/dir_refs.go b/pkg/sentry/fsimpl/sys/dir_refs.go
index d42edb20e..89609b198 100644
--- a/pkg/sentry/fsimpl/sys/dir_refs.go
+++ b/pkg/sentry/fsimpl/sys/dir_refs.go
@@ -1,10 +1,10 @@
 package sys
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )
diff --git a/pkg/sentry/fsimpl/tmpfs/inode_refs.go b/pkg/sentry/fsimpl/tmpfs/inode_refs.go
index 4f4037adb..dbf0b2766 100644
--- a/pkg/sentry/fsimpl/tmpfs/inode_refs.go
+++ b/pkg/sentry/fsimpl/tmpfs/inode_refs.go
@@ -1,10 +1,10 @@
 package tmpfs
 
 import (
+	"fmt"
 	"runtime"
 	"sync/atomic"
 
-	"fmt"
 	"gvisor.dev/gvisor/pkg/log"
 	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
 )