114 lines
3.5 KiB
Go
114 lines
3.5 KiB
Go
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// Copyright 2021 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 lisafs
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import (
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"gvisor.dev/gvisor/pkg/sync"
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)
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// Server serves a filesystem tree. Multiple connections on different mount
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// points can be started on a server. The server provides utilities to safely
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// modify the filesystem tree across its connections (mount points). Note that
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// it does not support synchronizing filesystem tree mutations across other
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// servers serving the same filesystem subtree. Server also manages the
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// lifecycle of all connections.
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type Server struct {
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// connWg counts the number of active connections being tracked.
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connWg sync.WaitGroup
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// RenameMu synchronizes rename operations within this filesystem tree.
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RenameMu sync.RWMutex
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// handlers is a list of RPC handlers which can be indexed by the handler's
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// corresponding MID.
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handlers []RPCHandler
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// mountPoints keeps track of all the mount points this server serves.
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mpMu sync.RWMutex
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mountPoints []*ControlFD
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// impl is the server implementation which embeds this server.
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impl ServerImpl
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}
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// Init must be called before first use of server.
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func (s *Server) Init(impl ServerImpl) {
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s.impl = impl
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s.handlers = handlers[:]
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}
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// InitTestOnly is the same as Init except that it allows to swap out the
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// underlying handlers with something custom. This is for test only.
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func (s *Server) InitTestOnly(impl ServerImpl, handlers []RPCHandler) {
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s.impl = impl
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s.handlers = handlers
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}
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// WithRenameReadLock invokes fn with the server's rename mutex locked for
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// reading. This ensures that no rename operations occur concurrently.
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func (s *Server) WithRenameReadLock(fn func() error) error {
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s.RenameMu.RLock()
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err := fn()
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s.RenameMu.RUnlock()
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return err
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}
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// StartConnection starts the connection on a separate goroutine and tracks it.
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func (s *Server) StartConnection(c *Connection) {
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s.connWg.Add(1)
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go func() {
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c.Run()
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s.connWg.Done()
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}()
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}
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// Wait waits for all connections started via StartConnection() to terminate.
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func (s *Server) Wait() {
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s.connWg.Wait()
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}
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func (s *Server) addMountPoint(root *ControlFD) {
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s.mpMu.Lock()
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defer s.mpMu.Unlock()
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s.mountPoints = append(s.mountPoints, root)
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}
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func (s *Server) forEachMountPoint(fn func(root *ControlFD)) {
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s.mpMu.RLock()
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defer s.mpMu.RUnlock()
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for _, mp := range s.mountPoints {
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fn(mp)
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}
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}
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// ServerImpl contains the implementation details for a Server.
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// Implementations of ServerImpl should contain their associated Server by
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// value as their first field.
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type ServerImpl interface {
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// Mount is called when a Mount RPC is made. It mounts the connection at
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// mountPath.
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//
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// Precondition: mountPath == path.Clean(mountPath).
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Mount(c *Connection, mountPath string) (ControlFDImpl, Inode, error)
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// SupportedMessages returns a list of messages that the server
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// implementation supports.
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SupportedMessages() []MID
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// MaxMessageSize is the maximum payload length (in bytes) that can be sent
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// to this server implementation.
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MaxMessageSize() uint32
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}
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