Drop final amutex uses.

These amutex lock uses are limited to vfs1 and provide questionable utility.
They protect only offset access, and not blocking operations. In order to
completely remove amutex, drop these uses. The amutex package will be removed
in a subsequent commit, which migrates other (less questionable) uses to a new
Context API.

PiperOrigin-RevId: 409716979

pkg/sentry/fs/BUILD

@@ -46,7 +46,6 @@ go_library(
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",
-        "//pkg/amutex",
         "//pkg/context",
         "//pkg/errors/linuxerr",
         "//pkg/hostarch",

pkg/sentry/fs/file.go

@@ -18,7 +18,6 @@ import (
 	"math"
 	"sync/atomic"
 
-	"gvisor.dev/gvisor/pkg/amutex"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/errors/linuxerr"
 	"gvisor.dev/gvisor/pkg/refs"
@@ -91,7 +90,7 @@ type File struct {
 	// mu is dual-purpose: first, to make read(2) and write(2) thread-safe
 	// in conformity with POSIX, and second, to cancel operations before they
 	// begin in response to interruptions (i.e. signals).
-	mu amutex.AbortableMutex `state:"nosave"`
+	mu sync.Mutex `state:"nosave"`
 
 	// FileOperations implements file system specific behavior for this File.
 	FileOperations FileOperations `state:"wait"`
@@ -113,7 +112,6 @@ func NewFile(ctx context.Context, dirent *Dirent, flags FileFlags, fops FileOper
 		FileOperations: fops,
 		flags:          flags,
 	}
-	f.mu.Init()
 	f.EnableLeakCheck("fs.File")
 	return &f
 }
@@ -197,9 +195,7 @@ func (f *File) EventUnregister(e *waiter.Entry) {
 //
 // Returns linuxerr.ErrInterrupted if seeking was interrupted.
 func (f *File) Seek(ctx context.Context, whence SeekWhence, offset int64) (int64, error) {
-	if !f.mu.Lock(ctx) {
-		return 0, linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
 
 	newOffset, err := f.FileOperations.Seek(ctx, f, whence, offset)
@@ -219,9 +215,7 @@ func (f *File) Seek(ctx context.Context, whence SeekWhence, offset int64) (int64
 //
 // Returns linuxerr.ErrInterrupted if reading was interrupted.
 func (f *File) Readdir(ctx context.Context, serializer DentrySerializer) error {
-	if !f.mu.Lock(ctx) {
-		return linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
 
 	offset, err := f.FileOperations.Readdir(ctx, f, serializer)
@@ -236,17 +230,13 @@ func (f *File) Readdir(ctx context.Context, serializer DentrySerializer) error {
 func (f *File) Readv(ctx context.Context, dst usermem.IOSequence) (int64, error) {
 	start := fsmetric.StartReadWait()
 	defer fsmetric.FinishReadWait(fsmetric.ReadWait, start)
-
-	if !f.mu.Lock(ctx) {
-		return 0, linuxerr.ErrInterrupted
-	}
-
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	fsmetric.Reads.Increment()
 	n, err := f.FileOperations.Read(ctx, f, dst, f.offset)
 	if n > 0 && !f.flags.NonSeekable {
 		atomic.AddInt64(&f.offset, n)
 	}
-	f.mu.Unlock()
 	return n, err
 }
 
@@ -258,14 +248,10 @@ func (f *File) Readv(ctx context.Context, dst usermem.IOSequence) (int64, error)
 func (f *File) Preadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
 	start := fsmetric.StartReadWait()
 	defer fsmetric.FinishReadWait(fsmetric.ReadWait, start)
-
-	if !f.mu.Lock(ctx) {
-		return 0, linuxerr.ErrInterrupted
-	}
-
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	fsmetric.Reads.Increment()
 	n, err := f.FileOperations.Read(ctx, f, dst, offset)
-	f.mu.Unlock()
 	return n, err
 }
 
@@ -278,15 +264,13 @@ func (f *File) Preadv(ctx context.Context, dst usermem.IOSequence, offset int64)
 //
 // Returns linuxerr.ErrInterrupted if writing was interrupted.
 func (f *File) Writev(ctx context.Context, src usermem.IOSequence) (int64, error) {
-	if !f.mu.Lock(ctx) {
-		return 0, linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
+	defer f.mu.Unlock()
 	unlockAppendMu := f.Dirent.Inode.lockAppendMu(f.Flags().Append)
 	// Handle append mode.
 	if f.Flags().Append {
 		if err := f.offsetForAppend(ctx, &f.offset); err != nil {
 			unlockAppendMu()
-			f.mu.Unlock()
 			return 0, err
 		}
 	}
@@ -296,7 +280,6 @@ func (f *File) Writev(ctx context.Context, src usermem.IOSequence) (int64, error
 	switch {
 	case ok && limit == 0:
 		unlockAppendMu()
-		f.mu.Unlock()
 		return 0, linuxerr.ErrExceedsFileSizeLimit
 	case ok:
 		src = src.TakeFirst64(limit)
@@ -308,7 +291,6 @@ func (f *File) Writev(ctx context.Context, src usermem.IOSequence) (int64, error
 		atomic.StoreInt64(&f.offset, f.offset+n)
 	}
 	unlockAppendMu()
-	f.mu.Unlock()
 	return n, err
 }
 
@@ -383,11 +365,8 @@ func (f *File) checkLimit(ctx context.Context, offset int64) (int64, bool) {
 //
 // Returns linuxerr.ErrInterrupted if syncing was interrupted.
 func (f *File) Fsync(ctx context.Context, start int64, end int64, syncType SyncType) error {
-	if !f.mu.Lock(ctx) {
-		return linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
-
 	return f.FileOperations.Fsync(ctx, f, start, end, syncType)
 }
 
@@ -395,11 +374,8 @@ func (f *File) Fsync(ctx context.Context, start int64, end int64, syncType SyncT
 //
 // Returns linuxerr.ErrInterrupted if syncing was interrupted.
 func (f *File) Flush(ctx context.Context) error {
-	if !f.mu.Lock(ctx) {
-		return linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
-
 	return f.FileOperations.Flush(ctx, f)
 }
 
@@ -407,11 +383,8 @@ func (f *File) Flush(ctx context.Context) error {
 //
 // Returns linuxerr.ErrInterrupted if interrupted.
 func (f *File) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
-	if !f.mu.Lock(ctx) {
-		return linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
-
 	return f.FileOperations.ConfigureMMap(ctx, f, opts)
 }
 
@@ -419,11 +392,8 @@ func (f *File) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
 //
 // Returns linuxerr.ErrInterrupted if interrupted.
 func (f *File) UnstableAttr(ctx context.Context) (UnstableAttr, error) {
-	if !f.mu.Lock(ctx) {
-		return UnstableAttr{}, linuxerr.ErrInterrupted
-	}
+	f.mu.Lock()
 	defer f.mu.Unlock()
-
 	return f.FileOperations.UnstableAttr(ctx, f)
 }
 

pkg/sentry/fs/file_state.go

@@ -24,7 +24,6 @@ func (f *File) beforeSave() {
 
 // afterLoad is invoked by stateify.
 func (f *File) afterLoad() {
-	f.mu.Init()
 	if f.flags.Async && f.async != nil {
 		f.async.Register(f)
 	}

pkg/sentry/fs/splice.go

@@ -25,6 +25,7 @@ import (
 // Splice moves data to this file, directly from another.
 //
 // Offsets are updated only if DstOffset and SrcOffset are set.
+// +checklocksignore
 func Splice(ctx context.Context, dst *File, src *File, opts SpliceOpts) (int64, error) {
 	// Verify basic file flag permissions.
 	if !dst.Flags().Write || !src.Flags().Read {
@@ -53,44 +54,28 @@ func Splice(ctx context.Context, dst *File, src *File, opts SpliceOpts) (int64,
 		switch {
 		case dst.UniqueID < src.UniqueID:
 			// Acquire dst first.
-			if !dst.mu.Lock(ctx) {
-				return 0, linuxerr.ErrInterrupted
-			}
-			if !src.mu.Lock(ctx) {
-				dst.mu.Unlock()
-				return 0, linuxerr.ErrInterrupted
-			}
+			dst.mu.Lock()
+			src.mu.Lock()
 		case dst.UniqueID > src.UniqueID:
 			// Acquire src first.
-			if !src.mu.Lock(ctx) {
-				return 0, linuxerr.ErrInterrupted
-			}
-			if !dst.mu.Lock(ctx) {
-				src.mu.Unlock()
-				return 0, linuxerr.ErrInterrupted
-			}
+			src.mu.Lock()
+			dst.mu.Lock()
 		case dst.UniqueID == src.UniqueID:
 			// Acquire only one lock; it's the same file. This is a
 			// bit of a edge case, but presumably it's possible.
-			if !dst.mu.Lock(ctx) {
-				return 0, linuxerr.ErrInterrupted
-			}
-			srcLock = false // Only need one unlock.
+			dst.mu.Lock()
+			srcLock = false
 		}
 		// Use both offsets (locked).
 		opts.DstStart = dst.offset
 		opts.SrcStart = src.offset
 	case dstLock:
 		// Acquire only dst.
-		if !dst.mu.Lock(ctx) {
-			return 0, linuxerr.ErrInterrupted
-		}
+		dst.mu.Lock()
 		opts.DstStart = dst.offset // Safe: locked.
 	case srcLock:
 		// Acquire only src.
-		if !src.mu.Lock(ctx) {
-			return 0, linuxerr.ErrInterrupted
-		}
+		src.mu.Lock()
 		opts.SrcStart = src.offset // Safe: locked.
 	}
 

pkg/sentry/fsimpl/tmpfs/BUILD

@@ -56,7 +56,6 @@ go_library(
     visibility = ["//pkg/sentry:internal"],
     deps = [
         "//pkg/abi/linux",
-        "//pkg/amutex",
         "//pkg/context",
         "//pkg/errors/linuxerr",
         "//pkg/fspath",

pkg/sentry/kernel/BUILD

@@ -219,7 +219,6 @@ go_library(
         "//pkg/abi",
         "//pkg/abi/linux",
         "//pkg/abi/linux/errno",
-        "//pkg/amutex",
         "//pkg/bitmap",
         "//pkg/bits",
         "//pkg/bpf",