319 lines
8.0 KiB
Go
319 lines
8.0 KiB
Go
// Copyright 2015 Google Inc. All Rights Reserved.
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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 fuse
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import (
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"fmt"
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"log"
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"path"
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"runtime"
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"sync"
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"golang.org/x/net/context"
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"github.com/jacobsa/fuse/fuseops"
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"github.com/jacobsa/fuse/internal/fusekernel"
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"github.com/jacobsa/fuse/internal/fuseshim"
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)
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// A connection to the fuse kernel process.
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type Connection struct {
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debugLogger *log.Logger
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errorLogger *log.Logger
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wrapped *fuseshim.Conn
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// The context from which all op contexts inherit.
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parentCtx context.Context
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// For logging purposes only.
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nextOpID uint32
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mu sync.Mutex
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// A map from fuse "unique" request ID (*not* the op ID for logging used
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// above) to a function that cancel's its associated context.
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//
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// GUARDED_BY(mu)
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cancelFuncs map[uint64]func()
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}
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// Responsibility for closing the wrapped connection is transferred to the
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// result. You must call c.close() eventually.
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//
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// The loggers may be nil.
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func newConnection(
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parentCtx context.Context,
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debugLogger *log.Logger,
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errorLogger *log.Logger,
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wrapped *fuseshim.Conn) (c *Connection, err error) {
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c = &Connection{
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debugLogger: debugLogger,
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errorLogger: errorLogger,
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wrapped: wrapped,
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parentCtx: parentCtx,
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cancelFuncs: make(map[uint64]func()),
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}
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return
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}
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// Log information for an operation with the given ID. calldepth is the depth
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// to use when recovering file:line information with runtime.Caller.
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func (c *Connection) debugLog(
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opID uint32,
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calldepth int,
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format string,
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v ...interface{}) {
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if c.debugLogger == nil {
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return
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}
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// Get file:line info.
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var file string
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var line int
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var ok bool
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_, file, line, ok = runtime.Caller(calldepth)
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if !ok {
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file = "???"
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}
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fileLine := fmt.Sprintf("%v:%v", path.Base(file), line)
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// Format the actual message to be printed.
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msg := fmt.Sprintf(
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"Op 0x%08x %24s] %v",
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opID,
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fileLine,
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fmt.Sprintf(format, v...))
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// Print it.
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c.debugLogger.Println(msg)
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}
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// LOCKS_EXCLUDED(c.mu)
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func (c *Connection) recordCancelFunc(
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fuseID uint64,
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f func()) {
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c.mu.Lock()
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defer c.mu.Unlock()
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if _, ok := c.cancelFuncs[fuseID]; ok {
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panic(fmt.Sprintf("Already have cancel func for request %v", fuseID))
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}
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c.cancelFuncs[fuseID] = f
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}
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// Set up state for an op that is about to be returned to the user, given its
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// underlying fuse opcode and request ID.
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//
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// Return a context that should be used for the op.
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//
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// LOCKS_EXCLUDED(c.mu)
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func (c *Connection) beginOp(
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opCode uint32,
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fuseID uint64) (ctx context.Context) {
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// Start with the parent context.
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ctx = c.parentCtx
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// Set up a cancellation function.
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//
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// Special case: On Darwin, osxfuse aggressively reuses "unique" request IDs.
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// This matters for Forget requests, which have no reply associated and
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// therefore have IDs that are immediately eligible for reuse. For these, we
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// should not record any state keyed on their ID.
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//
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// Cf. https://github.com/osxfuse/osxfuse/issues/208
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if opCode != fusekernel.OpForget {
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var cancel func()
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ctx, cancel = context.WithCancel(ctx)
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c.recordCancelFunc(fuseID, cancel)
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}
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return
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}
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// Clean up all state associated with an op to which the user has responded,
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// given its underlying fuse opcode and request ID. This must be called before
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// a response is sent to the kernel, to avoid a race where the request's ID
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// might be reused by osxfuse.
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//
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// LOCKS_EXCLUDED(c.mu)
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func (c *Connection) finishOp(
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opCode uint32,
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fuseID uint64) {
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c.mu.Lock()
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defer c.mu.Unlock()
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// Even though the op is finished, context.WithCancel requires us to arrange
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// for the cancellation function to be invoked. We also must remove it from
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// our map.
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//
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// Special case: we don't do this for Forget requests. See the note in
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// beginOp above.
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if opCode != fusekernel.OpForget {
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cancel, ok := c.cancelFuncs[fuseID]
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if !ok {
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panic(fmt.Sprintf("Unknown request ID in finishOp: %v", fuseID))
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}
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cancel()
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delete(c.cancelFuncs, fuseID)
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}
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}
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// LOCKS_EXCLUDED(c.mu)
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func (c *Connection) handleInterrupt(fuseID uint64) {
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c.mu.Lock()
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defer c.mu.Unlock()
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// NOTE(jacobsa): fuse.txt in the Linux kernel documentation
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// (https://goo.gl/H55Dnr) defines the kernel <-> userspace protocol for
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// interrupts.
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//
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// In particular, my reading of it is that an interrupt request cannot be
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// delivered to userspace before the original request. The part about the
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// race and EAGAIN appears to be aimed at userspace programs that
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// concurrently process requests (cf. http://goo.gl/BES2rs).
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//
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// So in this method if we can't find the ID to be interrupted, it means that
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// the request has already been replied to.
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//
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// Cf. https://github.com/osxfuse/osxfuse/issues/208
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// Cf. http://comments.gmane.org/gmane.comp.file-systems.fuse.devel/14675
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cancel, ok := c.cancelFuncs[fuseID]
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if !ok {
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return
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}
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cancel()
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}
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// Read the next op from the kernel process. Return io.EOF if the kernel has
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// closed the connection.
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//
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// This function delivers ops in exactly the order they are received from
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// /dev/fuse. It must not be called multiple times concurrently.
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//
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// LOCKS_EXCLUDED(c.mu)
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func (c *Connection) ReadOp() (op fuseops.Op, err error) {
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// Keep going until we find a request we know how to convert.
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for {
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// Read the next message from the fuseshim connection.
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var m *fuseshim.Message
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m, err = c.wrapped.ReadMessage()
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if err != nil {
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return
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}
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// Choose an ID for this operation for the purposes of logging.
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opID := c.nextOpID
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c.nextOpID++
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// Set up op dependencies.
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opCtx := c.beginOp(m.Hdr.Opcode, m.Hdr.Unique)
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var debugLogForOp func(int, string, ...interface{})
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if c.debugLogger != nil {
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debugLogForOp = func(calldepth int, format string, v ...interface{}) {
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c.debugLog(opID, calldepth+1, format, v...)
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}
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}
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sendReply := func(
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op fuseops.Op,
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fuseID uint64,
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replyMsg []byte,
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opErr error) (err error) {
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// Make sure we destroy the message, as required by
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// fuseshim.Connection.ReadMessage.
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defer m.Destroy()
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// Clean up state for this op.
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c.finishOp(m.Hdr.Opcode, m.Hdr.Unique)
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// Debug logging
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if c.debugLogger != nil {
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if opErr == nil {
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op.Logf("-> OK: %s", op.DebugString())
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} else {
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op.Logf("-> error: %v", opErr)
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}
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}
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// Error logging
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if opErr != nil && c.errorLogger != nil {
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c.errorLogger.Printf("(%s) error: %v", op.ShortDesc(), opErr)
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}
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// Send the reply to the kernel.
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err = c.wrapped.WriteToKernel(replyMsg)
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if err != nil {
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err = fmt.Errorf("WriteToKernel: %v", err)
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return
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}
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return
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}
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// Convert the message to an Op.
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op, err = fuseops.Convert(
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opCtx,
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m,
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c.wrapped.Protocol(),
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debugLogForOp,
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c.errorLogger,
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sendReply)
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if err != nil {
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err = fmt.Errorf("fuseops.Convert: %v", err)
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return
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}
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// Log the receipt of the operation.
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c.debugLog(opID, 1, "<- %v", op.ShortDesc())
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// Special case: responding to statfs is required to make mounting work on
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// OS X. We don't currently expose the capability for the file system to
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// intercept this.
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if _, ok := op.(*fuseops.InternalStatFSOp); ok {
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op.Respond(nil)
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continue
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}
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// Special case: handle interrupt requests.
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if interruptOp, ok := op.(*fuseops.InternalInterruptOp); ok {
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c.handleInterrupt(interruptOp.FuseID)
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continue
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}
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return
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}
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}
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func (c *Connection) waitForReady() (err error) {
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<-c.wrapped.Ready
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err = c.wrapped.MountError
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return
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}
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// Close the connection. Must not be called until operations that were read
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// from the connection have been responded to.
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func (c *Connection) close() (err error) {
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err = c.wrapped.Close()
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return
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}
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