3 files changed, 54 insertions, 48 deletions
diff --git a/pkg/sentry/vfs/epoll.go b/pkg/sentry/vfs/epoll.go
index a98aac52b..072655fe8 100644
--- a/pkg/sentry/vfs/epoll.go
+++ b/pkg/sentry/vfs/epoll.go
@@ -204,8 +204,8 @@ func (ep *EpollInstance) AddInterest(file *FileDescription, num int32, event lin
 	file.EventRegister(&epi.waiter, wmask)
 
 	// Check if the file is already ready.
-	if file.Readiness(wmask)&wmask != 0 {
-		epi.Callback(nil)
+	if m := file.Readiness(wmask) & wmask; m != 0 {
+		epi.Callback(nil, m)
 	}
 
 	// Add epi to file.epolls so that it is removed when the last
@@ -274,8 +274,8 @@ func (ep *EpollInstance) ModifyInterest(file *FileDescription, num int32, event
 	file.EventRegister(&epi.waiter, wmask)
 
 	// Check if the file is already ready with the new mask.
-	if file.Readiness(wmask)&wmask != 0 {
-		epi.Callback(nil)
+	if m := file.Readiness(wmask) & wmask; m != 0 {
+		epi.Callback(nil, m)
 	}
 
 	return nil
@@ -311,7 +311,7 @@ func (ep *EpollInstance) DeleteInterest(file *FileDescription, num int32) error
 }
 
 // Callback implements waiter.EntryCallback.Callback.
-func (epi *epollInterest) Callback(*waiter.Entry) {
+func (epi *epollInterest) Callback(*waiter.Entry, waiter.EventMask) {
 	newReady := false
 	epi.epoll.mu.Lock()
 	if !epi.ready {
diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index f9e39a94c..5321ac80a 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -15,6 +15,7 @@
 package vfs
 
 import (
+	"io"
 	"sync/atomic"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
@@ -43,7 +44,7 @@ import (
 type FileDescription struct {
 	FileDescriptionRefs
 
-	// flagsMu protects statusFlags and asyncHandler below.
+	// flagsMu protects `statusFlags`, `saved`, and `asyncHandler` below.
 	flagsMu sync.Mutex `state:"nosave"`
 
 	// statusFlags contains status flags, "initialized by open(2) and possibly
@@ -52,6 +53,11 @@ type FileDescription struct {
 	// access to asyncHandler.
 	statusFlags uint32
 
+	// saved is true after beforeSave is called. This is used to prevent
+	// double-unregistration of asyncHandler. This does not work properly for
+	// save-resume, which is not currently supported in gVisor (see b/26588733).
+	saved bool `state:"nosave"`
+
 	// asyncHandler handles O_ASYNC signal generation. It is set with the
 	// F_SETOWN or F_SETOWN_EX fcntls. For asyncHandler to be used, O_ASYNC must
 	// also be set by fcntl(2).
@@ -184,7 +190,7 @@ func (fd *FileDescription) DecRef(ctx context.Context) {
 		}
 		fd.vd.DecRef(ctx)
 		fd.flagsMu.Lock()
-		if fd.statusFlags&linux.O_ASYNC != 0 && fd.asyncHandler != nil {
+		if !fd.saved && fd.statusFlags&linux.O_ASYNC != 0 && fd.asyncHandler != nil {
 			fd.asyncHandler.Unregister(fd)
 		}
 		fd.asyncHandler = nil
@@ -834,44 +840,27 @@ func (fd *FileDescription) SetAsyncHandler(newHandler func() FileAsync) FileAsyn
 	return fd.asyncHandler
 }
 
-// FileReadWriteSeeker is a helper struct to pass a FileDescription as
-// io.Reader/io.Writer/io.ReadSeeker/io.ReaderAt/io.WriterAt/etc.
-type FileReadWriteSeeker struct {
-	FD    *FileDescription
-	Ctx   context.Context
-	ROpts ReadOptions
-	WOpts WriteOptions
-}
-
-// ReadAt implements io.ReaderAt.ReadAt.
-func (f *FileReadWriteSeeker) ReadAt(p []byte, off int64) (int, error) {
-	dst := usermem.BytesIOSequence(p)
-	n, err := f.FD.PRead(f.Ctx, dst, off, f.ROpts)
-	return int(n), err
-}
-
-// Read implements io.ReadWriteSeeker.Read.
-func (f *FileReadWriteSeeker) Read(p []byte) (int, error) {
-	dst := usermem.BytesIOSequence(p)
-	n, err := f.FD.Read(f.Ctx, dst, f.ROpts)
-	return int(n), err
-}
-
-// Seek implements io.ReadWriteSeeker.Seek.
-func (f *FileReadWriteSeeker) Seek(offset int64, whence int) (int64, error) {
-	return f.FD.Seek(f.Ctx, offset, int32(whence))
-}
-
-// WriteAt implements io.WriterAt.WriteAt.
-func (f *FileReadWriteSeeker) WriteAt(p []byte, off int64) (int, error) {
-	dst := usermem.BytesIOSequence(p)
-	n, err := f.FD.PWrite(f.Ctx, dst, off, f.WOpts)
-	return int(n), err
-}
-
-// Write implements io.ReadWriteSeeker.Write.
-func (f *FileReadWriteSeeker) Write(p []byte) (int, error) {
-	buf := usermem.BytesIOSequence(p)
-	n, err := f.FD.Write(f.Ctx, buf, f.WOpts)
-	return int(n), err
+// CopyRegularFileData copies data from srcFD to dstFD until reading from srcFD
+// returns EOF or an error. It returns the number of bytes copied.
+func CopyRegularFileData(ctx context.Context, dstFD, srcFD *FileDescription) (int64, error) {
+	done := int64(0)
+	buf := usermem.BytesIOSequence(make([]byte, 32*1024)) // arbitrary buffer size
+	for {
+		readN, readErr := srcFD.Read(ctx, buf, ReadOptions{})
+		if readErr != nil && readErr != io.EOF {
+			return done, readErr
+		}
+		src := buf.TakeFirst64(readN)
+		for src.NumBytes() != 0 {
+			writeN, writeErr := dstFD.Write(ctx, src, WriteOptions{})
+			done += writeN
+			src = src.DropFirst64(writeN)
+			if writeErr != nil {
+				return done, writeErr
+			}
+		}
+		if readErr == io.EOF {
+			return done, nil
+		}
+	}
 }
diff --git a/pkg/sentry/vfs/save_restore.go b/pkg/sentry/vfs/save_restore.go
index 7723ed643..8f070ed53 100644
--- a/pkg/sentry/vfs/save_restore.go
+++ b/pkg/sentry/vfs/save_restore.go
@@ -18,8 +18,10 @@ import (
 	"fmt"
 	"sync/atomic"
 
+	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/refsvfs2"
+	"gvisor.dev/gvisor/pkg/waiter"
 )
 
 // FilesystemImplSaveRestoreExtension is an optional extension to
@@ -120,5 +122,20 @@ func (mnt *Mount) afterLoad() {
 func (epi *epollInterest) afterLoad() {
 	// Mark all epollInterests as ready after restore so that the next call to
 	// EpollInstance.ReadEvents() rechecks their readiness.
-	epi.Callback(nil)
+	epi.Callback(nil, waiter.EventMaskFromLinux(epi.mask))
+}
+
+// beforeSave is called by stateify.
+func (fd *FileDescription) beforeSave() {
+	fd.saved = true
+	if fd.statusFlags&linux.O_ASYNC != 0 && fd.asyncHandler != nil {
+		fd.asyncHandler.Unregister(fd)
+	}
+}
+
+// afterLoad is called by stateify.
+func (fd *FileDescription) afterLoad() {
+	if fd.statusFlags&linux.O_ASYNC != 0 && fd.asyncHandler != nil {
+		fd.asyncHandler.Register(fd)
+	}
 }