github.com/metacubex/gvisor@v0.0.0-20240320004321-933faba989ec/pkg/sentry/fsimpl/devtmpfs/devtmpfs.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package devtmpfs provides a singleton fsimpl/dev filesystem instance,
    16  // analogous to Linux's devtmpfs.
    17  package devtmpfs
    18  
    19  import (
    20  	"github.com/metacubex/gvisor/pkg/context"
    21  	"github.com/metacubex/gvisor/pkg/sentry/fsimpl/dev"
    22  	"github.com/metacubex/gvisor/pkg/sentry/kernel/auth"
    23  	"github.com/metacubex/gvisor/pkg/sentry/vfs"
    24  	"github.com/metacubex/gvisor/pkg/sync"
    25  )
    26  
    27  // Name is the default filesystem name.
    28  const Name = "devtmpfs"
    29  
    30  // FilesystemType implements vfs.FilesystemType.
    31  //
    32  // +stateify savable
    33  type FilesystemType struct {
    34  	initOnce sync.Once `state:"nosave"`
    35  	initErr  error
    36  
    37  	// fs is the tmpfs filesystem that backs all mounts of this FilesystemType.
    38  	// root is fs' root. fs and root are immutable.
    39  	fs   *vfs.Filesystem
    40  	root *vfs.Dentry
    41  }
    42  
    43  // Name implements vfs.FilesystemType.Name.
    44  func (*FilesystemType) Name() string {
    45  	return Name
    46  }
    47  
    48  // GetFilesystem implements vfs.FilesystemType.GetFilesystem.
    49  func (fst *FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
    50  	fst.initOnce.Do(func() {
    51  		fs, root, err := dev.FilesystemType{}.GetFilesystem(ctx, vfsObj, creds, source, opts)
    52  		if err != nil {
    53  			fst.initErr = err
    54  			return
    55  		}
    56  		fst.fs = fs
    57  		fst.root = root
    58  	})
    59  	if fst.initErr != nil {
    60  		return nil, nil, fst.initErr
    61  	}
    62  	fst.fs.IncRef()
    63  	fst.root.IncRef()
    64  	return fst.fs, fst.root, nil
    65  }
    66  
    67  // Release implements vfs.FilesystemType.Release.
    68  func (fst *FilesystemType) Release(ctx context.Context) {
    69  	if fst.fs != nil {
    70  		// Release the original reference obtained when creating the filesystem.
    71  		fst.root.DecRef(ctx)
    72  		fst.fs.DecRef(ctx)
    73  	}
    74  }