Merge release-20210806.0-46-ga77eaf2a9 (automated)

2 files changed, 50 insertions, 28 deletions

diff --git a/pkg/sentry/fsimpl/gofer/handle.go b/pkg/sentry/fsimpl/gofer/handle.go
index 5c57f6fea..02540a754 100644
--- a/pkg/sentry/fsimpl/gofer/handle.go
+++ b/pkg/sentry/fsimpl/gofer/handle.go
@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/hostfd"
+	"gvisor.dev/gvisor/pkg/sync"
 )
 
 // handle represents a remote "open file descriptor", consisting of an opened
@@ -130,3 +131,43 @@ func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, o
 	}
 	return uint64(n), cperr
 }
+
+type handleReadWriter struct {
+	ctx context.Context
+	h   *handle
+	off uint64
+}
+
+var handleReadWriterPool = sync.Pool{
+	New: func() interface{} {
+		return &handleReadWriter{}
+	},
+}
+
+func getHandleReadWriter(ctx context.Context, h *handle, offset int64) *handleReadWriter {
+	rw := handleReadWriterPool.Get().(*handleReadWriter)
+	rw.ctx = ctx
+	rw.h = h
+	rw.off = uint64(offset)
+	return rw
+}
+
+func putHandleReadWriter(rw *handleReadWriter) {
+	rw.ctx = nil
+	rw.h = nil
+	handleReadWriterPool.Put(rw)
+}
+
+// ReadToBlocks implements safemem.Reader.ReadToBlocks.
+func (rw *handleReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
+	n, err := rw.h.readToBlocksAt(rw.ctx, dsts, rw.off)
+	rw.off += n
+	return n, err
+}
+
+// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
+func (rw *handleReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
+	n, err := rw.h.writeFromBlocksAt(rw.ctx, srcs, rw.off)
+	rw.off += n
+	return n, err
+}
diff --git a/pkg/sentry/fsimpl/gofer/special_file.go b/pkg/sentry/fsimpl/gofer/special_file.go
index 144a1045e..8e3c41808 100644
--- a/pkg/sentry/fsimpl/gofer/special_file.go
+++ b/pkg/sentry/fsimpl/gofer/special_file.go
@@ -24,7 +24,6 @@ import (
 	"gvisor.dev/gvisor/pkg/fdnotifier"
 	"gvisor.dev/gvisor/pkg/metric"
 	"gvisor.dev/gvisor/pkg/p9"
-	"gvisor.dev/gvisor/pkg/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/fsmetric"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
@@ -229,23 +228,13 @@ func (fd *specialFileFD) PRead(ctx context.Context, dst usermem.IOSequence, offs
 		}
 	}
 
-	// Going through dst.CopyOutFrom() would hold MM locks around file
-	// operations of unknown duration. For regularFileFD, doing so is necessary
-	// to support mmap due to lock ordering; MM locks precede dentry.dataMu.
-	// That doesn't hold here since specialFileFD doesn't client-cache data.
-	// Just buffer the read instead.
-	buf := make([]byte, dst.NumBytes())
-	n, err := fd.handle.readToBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), uint64(offset))
+	rw := getHandleReadWriter(ctx, &fd.handle, offset)
+	n, err := dst.CopyOutFrom(ctx, rw)
+	putHandleReadWriter(rw)
 	if linuxerr.Equals(linuxerr.EAGAIN, err) {
 		err = linuxerr.ErrWouldBlock
 	}
-	if n == 0 {
-		return bufN, err
-	}
-	if cp, cperr := dst.CopyOut(ctx, buf[:n]); cperr != nil {
-		return bufN + int64(cp), cperr
-	}
-	return bufN + int64(n), err
+	return bufN + n, err
 }
 
 // Read implements vfs.FileDescriptionImpl.Read.
@@ -316,20 +305,15 @@ func (fd *specialFileFD) pwrite(ctx context.Context, src usermem.IOSequence, off
 		}
 	}
 
-	// Do a buffered write. See rationale in PRead.
-	buf := make([]byte, src.NumBytes())
-	copied, copyErr := src.CopyIn(ctx, buf)
-	if copied == 0 && copyErr != nil {
-		// Only return the error if we didn't get any data.
-		return 0, offset, copyErr
-	}
-	n, err := fd.handle.writeFromBlocksAt(ctx, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf[:copied])), uint64(offset))
+	rw := getHandleReadWriter(ctx, &fd.handle, offset)
+	n, err := src.CopyInTo(ctx, rw)
+	putHandleReadWriter(rw)
 	if linuxerr.Equals(linuxerr.EAGAIN, err) {
 		err = linuxerr.ErrWouldBlock
 	}
 	// Update offset if the offset is valid.
 	if offset >= 0 {
-		offset += int64(n)
+		offset += n
 	}
 	// Update file size for regular files.
 	if fd.isRegularFile {
@@ -340,10 +324,7 @@ func (fd *specialFileFD) pwrite(ctx context.Context, src usermem.IOSequence, off
 			atomic.StoreUint64(&d.size, uint64(offset))
 		}
 	}
-	if err != nil {
-		return int64(n), offset, err
-	}
-	return int64(n), offset, copyErr
+	return int64(n), offset, err
 }
 
 // Write implements vfs.FileDescriptionImpl.Write.