2019-07-30 01:32:45 +00:00
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// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ext
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import (
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"io"
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)
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// fileReader is used to abstact away the complexity of how the file data is
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// stored under the hood. Provides a method to get a file reader which can be
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// used to read file data without worrying about how it is organized on disk.
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type fileReader interface {
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// getFileReader returns a Reader implementation which can be used to read a
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// file. It abstracts away the complexity of how the file is actually
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// organized on disk. The reader is initialized with the passed offset.
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//
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// This reader is not meant to be retained across Read operations as it needs
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// to be reinitialized with the correct offset for every Read.
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2019-07-30 03:11:24 +00:00
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getFileReader(dev io.ReaderAt, blkSize uint64, offset uint64) io.Reader
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2019-07-30 01:32:45 +00:00
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}
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// regularFile represents a regular file's inode. This too follows the
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// inheritance pattern prevelant in the vfs layer described in
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// pkg/sentry/vfs/README.md.
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type regularFile struct {
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inode inode
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// This is immutable. The first field of fileReader implementations must be
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// regularFile to ensure temporality.
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impl fileReader
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}
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// newRegularFile is the regularFile constructor. It figures out what kind of
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// file this is and initializes the fileReader.
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2019-07-30 03:11:24 +00:00
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func newRegularFile(dev io.ReaderAt, blkSize uint64, inode inode) (*regularFile, error) {
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2019-07-30 01:32:45 +00:00
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regFile := regularFile{
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inode: inode,
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}
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inodeFlags := inode.diskInode.Flags()
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if inodeFlags.Extents {
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file, err := newExtentFile(dev, blkSize, regFile)
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if err != nil {
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return nil, err
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}
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file.regFile.inode.impl = &file.regFile
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return &file.regFile, nil
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}
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if inodeFlags.Inline {
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if inode.diskInode.Size() > 60 {
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panic("ext fs: inline file larger than 60 bytes")
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}
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file := newInlineFile(regFile)
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file.regFile.inode.impl = &file.regFile
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return &file.regFile, nil
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}
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file, err := newBlockMapFile(blkSize, regFile)
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if err != nil {
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return nil, err
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}
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file.regFile.inode.impl = &file.regFile
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return &file.regFile, nil
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}
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func (f *regularFile) blksUsed(blkSize uint64) uint64 {
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return (f.inode.diskInode.Size() + blkSize - 1) / blkSize
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}
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