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https://github.com/netbirdio/gvisor.git
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Jamie LiuandgVisor bot
f4b851067a
This partially reverts cl/578969556, but implements devtmpfs using fsimpl/dev (added by that CL). Note that the behavior of "devtmpfs" differs compared to before cl/578969556. Container runtime specs typically specify a tmpfs mount at /dev, which the container runtime is required to prepopulate with certain device files (https://github.com/opencontainers/runtime-spec/blob/main/config-linux.md#default-devices). Prior to cl/578969556, runsc did so by silently replacing tmpfs mounts at /dev with devtmpfs mounts. After that CL, runsc does so by silently replacing tmpfs mounts at /dev with fsimpl/dev mounts. The distinction is that devtmpfs is a singleton whereas fsimpl/dev is not, so in a multi-container sandbox, all containers shared the contents of /dev before cl/578969556, but not after that CL; this change was necessary due to differences in GPU/TPU accessibility between containers, and is also more consistent with runc (which also creates separate tmpfs mounts for /dev as specified). As a side effect, explicit devtmpfs mounts shared the same filesystem as every container's /dev before cl/578969556. Since the change to container /dev won't be reverted, our options now are: - All devtmpfs mounts share a single filesystem, which is distinct from any container's /dev. - Each devtmpfs mount gets a distinct filesystem. This CL chooses the former option for greater similarity to Linux devtmpfs semantics. (In runc, explicit devtmpfs mounts share a single filesystem, which is the *host's* /dev.) PiperOrigin-RevId: 589021563
75 lines
2.2 KiB
Go
75 lines
2.2 KiB
Go
// Copyright 2020 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 devtmpfs provides a singleton fsimpl/dev filesystem instance,
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// analogous to Linux's devtmpfs.
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package devtmpfs
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import (
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/sentry/fsimpl/dev"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/sync"
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)
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// Name is the default filesystem name.
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const Name = "devtmpfs"
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// FilesystemType implements vfs.FilesystemType.
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//
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// +stateify savable
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type FilesystemType struct {
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initOnce sync.Once `state:"nosave"`
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initErr error
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// fs is the tmpfs filesystem that backs all mounts of this FilesystemType.
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// root is fs' root. fs and root are immutable.
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fs *vfs.Filesystem
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root *vfs.Dentry
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}
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// Name implements vfs.FilesystemType.Name.
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func (*FilesystemType) Name() string {
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return Name
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}
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// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
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func (fst *FilesystemType) GetFilesystem(ctx context.Context, vfsObj *vfs.VirtualFilesystem, creds *auth.Credentials, source string, opts vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
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fst.initOnce.Do(func() {
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fs, root, err := dev.FilesystemType{}.GetFilesystem(ctx, vfsObj, creds, source, opts)
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if err != nil {
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fst.initErr = err
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return
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}
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fst.fs = fs
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fst.root = root
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})
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if fst.initErr != nil {
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return nil, nil, fst.initErr
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}
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fst.fs.IncRef()
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fst.root.IncRef()
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return fst.fs, fst.root, nil
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}
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// Release implements vfs.FilesystemType.Release.
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func (fst *FilesystemType) Release(ctx context.Context) {
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if fst.fs != nil {
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// Release the original reference obtained when creating the filesystem.
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fst.root.DecRef(ctx)
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fst.fs.DecRef(ctx)
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}
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}
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