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Merge pull request #3610 from MichaelEischer/windows-temp-files
Improve handling of temporary files on windows
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commit
89ee1cf9ee
10
changelog/unreleased/issue-3465
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10
changelog/unreleased/issue-3465
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@ -0,0 +1,10 @@
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Enhancement: Improve handling of temporary files on Windows
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In some cases restic failed to delete temporary files causing the current
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command to fail. This has been fixed by ensuring that Windows automatically
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deletes the file. In addition, temporary files are only written to disk if
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necessary to reduce disk writes.
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https://github.com/restic/restic/issues/3465
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https://github.com/restic/restic/issues/1551
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https://github.com/restic/restic/pull/3610
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@ -1,10 +1,14 @@
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package fs
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import (
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"io/ioutil"
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"math/rand"
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"os"
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"path/filepath"
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"strconv"
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"strings"
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"time"
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"golang.org/x/sys/windows"
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)
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// fixpath returns an absolute path on windows, so restic can open long file
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@ -30,9 +34,43 @@ func fixpath(name string) string {
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return name
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}
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// TempFile creates a temporary file.
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// TempFile creates a temporary file which is marked as delete-on-close
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func TempFile(dir, prefix string) (f *os.File, err error) {
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return ioutil.TempFile(dir, prefix)
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// slightly modified implementation of ioutil.TempFile(dir, prefix) to allow us to add
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// the FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE flags.
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// These provide two large benefits:
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// FILE_ATTRIBUTE_TEMPORARY tells Windows to keep the file in memory only if possible
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// which reduces the amount of unnecessary disk writes.
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// FILE_FLAG_DELETE_ON_CLOSE instructs Windows to automatically delete the file once
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// all file descriptors are closed.
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if dir == "" {
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dir = os.TempDir()
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}
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access := uint32(windows.GENERIC_READ | windows.GENERIC_WRITE)
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creation := uint32(windows.CREATE_NEW)
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share := uint32(0) // prevent other processes from accessing the file
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flags := uint32(windows.FILE_ATTRIBUTE_TEMPORARY | windows.FILE_FLAG_DELETE_ON_CLOSE)
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rnd := rand.New(rand.NewSource(time.Now().UnixNano()))
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for i := 0; i < 10000; i++ {
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randSuffix := strconv.Itoa(int(1e9 + rnd.Intn(1e9)%1e9))[1:]
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path := filepath.Join(dir, prefix+randSuffix)
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ptr, err := windows.UTF16PtrFromString(path)
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if err != nil {
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return nil, err
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}
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h, err := windows.CreateFile(ptr, access, share, nil, creation, flags, 0)
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if os.IsExist(err) {
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continue
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}
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return os.NewFile(uintptr(h), path), err
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}
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// Proper error handling is still to do
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return nil, os.ErrExist
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}
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// Chmod changes the mode of the named file to mode.
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35
internal/fs/file_windows_test.go
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35
internal/fs/file_windows_test.go
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package fs_test
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import (
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"errors"
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"os"
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"testing"
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"github.com/restic/restic/internal/fs"
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rtest "github.com/restic/restic/internal/test"
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)
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func TestTempFile(t *testing.T) {
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// create two temp files at the same time to check that the
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// collision avoidance works
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f, err := fs.TempFile("", "test")
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fn := f.Name()
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rtest.OK(t, err)
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f2, err := fs.TempFile("", "test")
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fn2 := f2.Name()
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rtest.OK(t, err)
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rtest.Assert(t, fn != fn2, "filenames don't differ %s", fn)
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_, err = os.Stat(fn)
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rtest.OK(t, err)
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_, err = os.Stat(fn2)
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rtest.OK(t, err)
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rtest.OK(t, f.Close())
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rtest.OK(t, f2.Close())
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_, err = os.Stat(fn)
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rtest.Assert(t, errors.Is(err, os.ErrNotExist), "err %s", err)
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_, err = os.Stat(fn2)
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rtest.Assert(t, errors.Is(err, os.ErrNotExist), "err %s", err)
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}
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