diff options
Diffstat (limited to 'pkg/sentry/fs/ext/extent_file.go')
-rw-r--r-- | pkg/sentry/fs/ext/extent_file.go | 233 |
1 files changed, 0 insertions, 233 deletions
diff --git a/pkg/sentry/fs/ext/extent_file.go b/pkg/sentry/fs/ext/extent_file.go deleted file mode 100644 index 44fb9c01f..000000000 --- a/pkg/sentry/fs/ext/extent_file.go +++ /dev/null @@ -1,233 +0,0 @@ -// 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" - "sort" - - "gvisor.dev/gvisor/pkg/binary" - "gvisor.dev/gvisor/pkg/sentry/fs/ext/disklayout" - "gvisor.dev/gvisor/pkg/syserror" -) - -// extentFile is a type of regular file which uses extents to store file data. -type extentFile struct { - regFile regularFile - - // root is the root extent node. This lives in the 60 byte diskInode.Data(). - // Immutable. - root disklayout.ExtentNode -} - -// Compiles only if extentFile implements io.ReaderAt. -var _ io.ReaderAt = (*extentFile)(nil) - -// newExtentFile is the extent file constructor. It reads the entire extent -// tree into memory. -// TODO(b/134676337): Build extent tree on demand to reduce memory usage. -func newExtentFile(regFile regularFile) (*extentFile, error) { - file := &extentFile{regFile: regFile} - file.regFile.impl = file - err := file.buildExtTree() - if err != nil { - return nil, err - } - return file, nil -} - -// buildExtTree builds the extent tree by reading it from disk by doing -// running a simple DFS. It first reads the root node from the inode struct in -// memory. Then it recursively builds the rest of the tree by reading it off -// disk. -// -// Precondition: inode flag InExtents must be set. -func (f *extentFile) buildExtTree() error { - rootNodeData := f.regFile.inode.diskInode.Data() - - binary.Unmarshal(rootNodeData[:disklayout.ExtentStructsSize], binary.LittleEndian, &f.root.Header) - - // Root node can not have more than 4 entries: 60 bytes = 1 header + 4 entries. - if f.root.Header.NumEntries > 4 { - // read(2) specifies that EINVAL should be returned if the file is unsuitable - // for reading. - return syserror.EINVAL - } - - f.root.Entries = make([]disklayout.ExtentEntryPair, f.root.Header.NumEntries) - for i, off := uint16(0), disklayout.ExtentStructsSize; i < f.root.Header.NumEntries; i, off = i+1, off+disklayout.ExtentStructsSize { - var curEntry disklayout.ExtentEntry - if f.root.Header.Height == 0 { - // Leaf node. - curEntry = &disklayout.Extent{} - } else { - // Internal node. - curEntry = &disklayout.ExtentIdx{} - } - binary.Unmarshal(rootNodeData[off:off+disklayout.ExtentStructsSize], binary.LittleEndian, curEntry) - f.root.Entries[i].Entry = curEntry - } - - // If this node is internal, perform DFS. - if f.root.Header.Height > 0 { - for i := uint16(0); i < f.root.Header.NumEntries; i++ { - var err error - if f.root.Entries[i].Node, err = f.buildExtTreeFromDisk(f.root.Entries[i].Entry); err != nil { - return err - } - } - } - - return nil -} - -// buildExtTreeFromDisk reads the extent tree nodes from disk and recursively -// builds the tree. Performs a simple DFS. It returns the ExtentNode pointed to -// by the ExtentEntry. -func (f *extentFile) buildExtTreeFromDisk(entry disklayout.ExtentEntry) (*disklayout.ExtentNode, error) { - var header disklayout.ExtentHeader - off := entry.PhysicalBlock() * f.regFile.inode.blkSize - err := readFromDisk(f.regFile.inode.dev, int64(off), &header) - if err != nil { - return nil, err - } - - entries := make([]disklayout.ExtentEntryPair, header.NumEntries) - for i, off := uint16(0), off+disklayout.ExtentStructsSize; i < header.NumEntries; i, off = i+1, off+disklayout.ExtentStructsSize { - var curEntry disklayout.ExtentEntry - if header.Height == 0 { - // Leaf node. - curEntry = &disklayout.Extent{} - } else { - // Internal node. - curEntry = &disklayout.ExtentIdx{} - } - - err := readFromDisk(f.regFile.inode.dev, int64(off), curEntry) - if err != nil { - return nil, err - } - entries[i].Entry = curEntry - } - - // If this node is internal, perform DFS. - if header.Height > 0 { - for i := uint16(0); i < header.NumEntries; i++ { - var err error - entries[i].Node, err = f.buildExtTreeFromDisk(entries[i].Entry) - if err != nil { - return nil, err - } - } - } - - return &disklayout.ExtentNode{header, entries}, nil -} - -// ReadAt implements io.ReaderAt.ReadAt. -func (f *extentFile) ReadAt(dst []byte, off int64) (int, error) { - if len(dst) == 0 { - return 0, nil - } - - if off < 0 { - return 0, syserror.EINVAL - } - - if uint64(off) >= f.regFile.inode.diskInode.Size() { - return 0, io.EOF - } - - return f.read(&f.root, uint64(off), dst) -} - -// read is the recursive step of extentFile.ReadAt which traverses the extent -// tree from the node passed and reads file data. -func (f *extentFile) read(node *disklayout.ExtentNode, off uint64, dst []byte) (int, error) { - // Perform a binary search for the node covering bytes starting at r.fileOff. - // A highly fragmented filesystem can have upto 340 entries and so linear - // search should be avoided. Finds the first entry which does not cover the - // file block we want and subtracts 1 to get the desired index. - fileBlk := uint32(off / f.regFile.inode.blkSize) - n := len(node.Entries) - found := sort.Search(n, func(i int) bool { - return node.Entries[i].Entry.FileBlock() > fileBlk - }) - 1 - - // We should be in this recursive step only if the data we want exists under - // the current node. - if found < 0 { - panic("searching for a file block in an extent entry which does not cover it") - } - - read := 0 - toRead := len(dst) - var curR int - var err error - for i := found; i < n && read < toRead; i++ { - if node.Header.Height == 0 { - curR, err = f.readFromExtent(node.Entries[i].Entry.(*disklayout.Extent), off, dst[read:]) - } else { - curR, err = f.read(node.Entries[i].Node, off, dst[read:]) - } - - read += curR - off += uint64(curR) - if err != nil { - return read, err - } - } - - return read, nil -} - -// readFromExtent reads file data from the extent. It takes advantage of the -// sequential nature of extents and reads file data from multiple blocks in one -// call. -// -// A non-nil error indicates that this is a partial read and there is probably -// more to read from this extent. The caller should propagate the error upward -// and not move to the next extent in the tree. -// -// A subsequent call to extentReader.Read should continue reading from where we -// left off as expected. -func (f *extentFile) readFromExtent(ex *disklayout.Extent, off uint64, dst []byte) (int, error) { - curFileBlk := uint32(off / f.regFile.inode.blkSize) - exFirstFileBlk := ex.FileBlock() - exLastFileBlk := exFirstFileBlk + uint32(ex.Length) // This is exclusive. - - // We should be in this recursive step only if the data we want exists under - // the current extent. - if curFileBlk < exFirstFileBlk || exLastFileBlk <= curFileBlk { - panic("searching for a file block in an extent which does not cover it") - } - - curPhyBlk := uint64(curFileBlk-exFirstFileBlk) + ex.PhysicalBlock() - readStart := curPhyBlk*f.regFile.inode.blkSize + (off % f.regFile.inode.blkSize) - - endPhyBlk := ex.PhysicalBlock() + uint64(ex.Length) - extentEnd := endPhyBlk * f.regFile.inode.blkSize // This is exclusive. - - toRead := int(extentEnd - readStart) - if len(dst) < toRead { - toRead = len(dst) - } - - n, _ := f.regFile.inode.dev.ReadAt(dst[:toRead], int64(readStart)) - if n < toRead { - return n, syserror.EIO - } - return n, nil -} |