138 lines
4.7 KiB
Go
138 lines
4.7 KiB
Go
// 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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"sync"
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"gvisor.dev/gvisor/pkg/sentry/context"
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"gvisor.dev/gvisor/pkg/sentry/fs/ext/disklayout"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/syserror"
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)
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// filesystem implements vfs.FilesystemImpl.
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type filesystem struct {
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// TODO(b/134676337): Remove when all methods have been implemented.
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vfs.FilesystemImpl
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vfsfs vfs.Filesystem
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// mu serializes changes to the Dentry tree and the usage of the read seeker.
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mu sync.Mutex
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// dev is the ReadSeeker for the underlying fs device. It is protected by mu.
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//
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// The ext filesystems aim to maximize locality, i.e. place all the data
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// blocks of a file close together. On a spinning disk, locality reduces the
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// amount of movement of the head hence speeding up IO operations. On an SSD
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// there are no moving parts but locality increases the size of each transer
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// request. Hence, having mutual exclusion on the read seeker while reading a
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// file *should* help in achieving the intended performance gains.
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//
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// Note: This synchronization was not coupled with the ReadSeeker itself
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// because we want to synchronize across read/seek operations for the
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// performance gains mentioned above. Helps enforcing one-file-at-a-time IO.
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dev io.ReadSeeker
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// inodeCache maps absolute inode numbers to the corresponding Inode struct.
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// Inodes should be removed from this once their reference count hits 0.
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//
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// Protected by mu because every addition and removal from this corresponds to
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// a change in the dentry tree.
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inodeCache map[uint32]*inode
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// sb represents the filesystem superblock. Immutable after initialization.
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sb disklayout.SuperBlock
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// bgs represents all the block group descriptors for the filesystem.
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// Immutable after initialization.
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bgs []disklayout.BlockGroup
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}
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// Compiles only if filesystem implements vfs.FilesystemImpl.
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var _ vfs.FilesystemImpl = (*filesystem)(nil)
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// getOrCreateInode gets the inode corresponding to the inode number passed in.
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// It creates a new one with the given inode number if one does not exist.
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//
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// Preconditions: must be holding fs.mu.
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func (fs *filesystem) getOrCreateInode(inodeNum uint32) (*inode, error) {
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if in, ok := fs.inodeCache[inodeNum]; ok {
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return in, nil
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}
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in, err := newInode(fs.dev, fs.sb, fs.bgs, inodeNum)
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if err != nil {
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return nil, err
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}
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fs.inodeCache[inodeNum] = in
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return in, nil
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}
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// Release implements vfs.FilesystemImpl.Release.
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func (fs *filesystem) Release() {
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}
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// Sync implements vfs.FilesystemImpl.Sync.
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func (fs *filesystem) Sync(ctx context.Context) error {
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// This is a readonly filesystem for now.
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return nil
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}
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// The vfs.FilesystemImpl functions below return EROFS because their respective
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// man pages say that EROFS must be returned if the path resolves to a file on
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// a read-only filesystem.
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// TODO(b/134676337): Implement path traversal and return EROFS only if the
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// path resolves to a Dentry within ext fs.
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// MkdirAt implements vfs.FilesystemImpl.MkdirAt.
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func (fs *filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.MkdirOptions) error {
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return syserror.EROFS
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}
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// MknodAt implements vfs.FilesystemImpl.MknodAt.
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func (fs *filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.MknodOptions) error {
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return syserror.EROFS
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}
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// RenameAt implements vfs.FilesystemImpl.RenameAt.
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func (fs *filesystem) RenameAt(ctx context.Context, rp *vfs.ResolvingPath, vd vfs.VirtualDentry, opts vfs.RenameOptions) error {
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return syserror.EROFS
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}
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// RmdirAt implements vfs.FilesystemImpl.RmdirAt.
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func (fs *filesystem) RmdirAt(ctx context.Context, rp *vfs.ResolvingPath) error {
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return syserror.EROFS
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}
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// SetStatAt implements vfs.FilesystemImpl.SetStatAt.
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func (fs *filesystem) SetStatAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.SetStatOptions) error {
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return syserror.EROFS
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}
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// SymlinkAt implements vfs.FilesystemImpl.SymlinkAt.
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func (fs *filesystem) SymlinkAt(ctx context.Context, rp *vfs.ResolvingPath, target string) error {
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return syserror.EROFS
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}
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// UnlinkAt implements vfs.FilesystemImpl.UnlinkAt.
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func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error {
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return syserror.EROFS
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}
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