ext: inode implementations.

PiperOrigin-RevId: 260624470

1 files changed, 90 insertions, 0 deletions

diff --git a/pkg/sentry/fs/ext/regular_file.go b/pkg/sentry/fs/ext/regular_file.go
new file mode 100644
index 000000000..9bf39acfe
--- /dev/null
+++ b/pkg/sentry/fs/ext/regular_file.go
@@ -0,0 +1,90 @@
+// Copyright 2019 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 ext
+
+import (
+	"io"
+)
+
+// fileReader is used to abstact away the complexity of how the file data is
+// stored under the hood. Provides a method to get a file reader which can be
+// used to read file data without worrying about how it is organized on disk.
+type fileReader interface {
+
+	// getFileReader returns a Reader implementation which can be used to read a
+	// file. It abstracts away the complexity of how the file is actually
+	// organized on disk. The reader is initialized with the passed offset.
+	//
+	// This reader is not meant to be retained across Read operations as it needs
+	// to be reinitialized with the correct offset for every Read.
+	//
+	// Precondition: Must hold the mutex of the filesystem containing dev while
+	//               using the Reader.
+	getFileReader(dev io.ReadSeeker, blkSize uint64, offset uint64) io.Reader
+}
+
+// regularFile represents a regular file's inode. This too follows the
+// inheritance pattern prevelant in the vfs layer described in
+// pkg/sentry/vfs/README.md.
+type regularFile struct {
+	inode inode
+
+	// This is immutable. The first field of fileReader implementations must be
+	// regularFile to ensure temporality.
+	impl fileReader
+}
+
+// newRegularFile is the regularFile constructor. It figures out what kind of
+// file this is and initializes the fileReader.
+//
+// Preconditions: Must hold the mutex of the filesystem containing dev.
+func newRegularFile(dev io.ReadSeeker, blkSize uint64, inode inode) (*regularFile, error) {
+	regFile := regularFile{
+		inode: inode,
+	}
+
+	inodeFlags := inode.diskInode.Flags()
+
+	if inodeFlags.Extents {
+		file, err := newExtentFile(dev, blkSize, regFile)
+		if err != nil {
+			return nil, err
+		}
+
+		file.regFile.inode.impl = &file.regFile
+		return &file.regFile, nil
+	}
+
+	if inodeFlags.Inline {
+		if inode.diskInode.Size() > 60 {
+			panic("ext fs: inline file larger than 60 bytes")
+		}
+
+		file := newInlineFile(regFile)
+		file.regFile.inode.impl = &file.regFile
+		return &file.regFile, nil
+	}
+
+	file, err := newBlockMapFile(blkSize, regFile)
+	if err != nil {
+		return nil, err
+	}
+	file.regFile.inode.impl = &file.regFile
+	return &file.regFile, nil
+}
+
+func (f *regularFile) blksUsed(blkSize uint64) uint64 {
+	return (f.inode.diskInode.Size() + blkSize - 1) / blkSize
+}