syncthing/lib/model/util.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
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package model
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import (
"context"
"errors"
"fmt"
"path/filepath"
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"time"
"github.com/prometheus/client_golang/prometheus"
"github.com/syncthing/syncthing/lib/fs"
)
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// inWritableDir calls fn(path), while making sure that the directory
// containing `path` is writable for the duration of the call.
func inWritableDir(fn func(string) error, targetFs fs.Filesystem, path string, ignorePerms bool) error {
dir := filepath.Dir(path)
info, err := targetFs.Stat(dir)
if err != nil {
return err
}
if !info.IsDir() {
return errors.New("Not a directory: " + path)
}
const permBits = fs.ModePerm | fs.ModeSetuid | fs.ModeSetgid | fs.ModeSticky
var parentErr error
if mode := info.Mode() & permBits; mode&0o200 == 0 {
// A non-writeable directory (for this user; we assume that's the
// relevant part). Temporarily change the mode so we can delete the
// file or directory inside it.
parentErr = targetFs.Chmod(dir, mode|0o700)
if parentErr != nil {
l.Debugf("Failed to make parent directory writable: %v", parentErr)
} else {
// Chmod succeeded, we should change the permissions back on the way
// out. If we fail we log the error as we have irrevocably messed up
// at this point. :( (The operation we were called to wrap has
// succeeded or failed on its own so returning an error to the
// caller is inappropriate.)
defer func() {
if err := targetFs.Chmod(dir, mode); err != nil && !fs.IsNotExist(err) {
logFn := l.Warnln
if ignorePerms {
logFn = l.Debugln
}
logFn("Failed to restore directory permissions after gaining write access:", err)
}
}()
}
}
err = fn(path)
if fs.IsPermission(err) && parentErr != nil {
err = fmt.Errorf("error after failing to make parent directory writable: %w", err)
}
return err
}
// addTimeUntilCancelled adds time to the counter for the duration of the
// Context. We do this piecemeal so that polling the counter during a long
// operation shows a relevant value, instead of the counter just increasing
// by a large amount at the end of the operation.
func addTimeUntilCancelled(ctx context.Context, counter prometheus.Counter) {
t0 := time.Now()
defer func() {
if dur := time.Since(t0).Seconds(); dur > 0 {
counter.Add(dur)
}
}()
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case t := <-ticker.C:
if dur := t.Sub(t0).Seconds(); dur > 0 {
counter.Add(dur)
}
t0 = t
case <-ctx.Done():
return
}
}
}