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// package cluster_test finds out what happens if multiple
// gocryptfs mounts write to one file concurrently
// (usually, nothing good).
//
// This use case is relevant for HPC clusters.
package cluster_test
import (
"bytes"
"errors"
"io"
"math/rand"
"os"
"sync"
"syscall"
"testing"
"github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
)
// With -sharedstorage (i.e. with fcntl byte-range locks) this test passes on all
// filesystems. Without, it passes on XFS but fails on ext4 and tmpfs.
//
// Quoting https://lists.samba.org/archive/samba-technical/2019-March/133050.html
//
// > It turns out that xfs respects POSIX w.r.t "atomic read/write" and
// > this is implemented by taking a file-wide shared lock on every
// > buffered read.
//
// Note that ext4 actually provides NO ATOMICITY AT ALL.
// Quoting https://stackoverflow.com/a/35256626 :
//
// > Linux 4.2.6 with ext4: update atomicity = 1 byte
//
// TestPoCTornWrite in this package confirms this.
//
// See also:
// - https://lore.kernel.org/linux-xfs/20190325001044.GA23020@dastard/
// Dave Chinner: XFS is the only linux filesystem that provides this behaviour.
func TestClusterConcurrentRW(t *testing.T) {
const fileSize = 100000 // arbitrary unaligned size with a partial block at the end
const writeSize = 5000 // arbitrary unaligned size that touches two ciphertext blocks
const readSize = 5000
cDir := test_helpers.InitFS(t)
mnt1 := cDir + ".mnt1"
mnt2 := cDir + ".mnt2"
test_helpers.MountOrFatal(t, cDir, mnt1, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt1)
test_helpers.MountOrFatal(t, cDir, mnt2, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt2)
f1, err := os.Create(mnt1 + "/foo")
if err != nil {
t.Fatal(err)
}
defer f1.Close()
// Preallocate space
_, err = f1.WriteAt(make([]byte, fileSize), 0)
if err != nil {
t.Fatal(err)
}
f2, err := os.OpenFile(mnt2+"/foo", os.O_RDWR, 0)
if err != nil {
t.Fatal(err)
}
defer f2.Close()
var wg sync.WaitGroup
const loops = 10000
writeThread := func(f *os.File) {
defer wg.Done()
buf := make([]byte, writeSize)
for i := 0; i < loops; i++ {
if t.Failed() {
return
}
off := rand.Int63n(int64(fileSize - len(buf) - 1))
_, err := f.WriteAt(buf, off)
if err != nil {
t.Errorf("writeThread iteration %d: WriteAt failed: %v", i, err)
return
}
}
}
readThread := func(f *os.File) {
defer wg.Done()
zeroBlock := make([]byte, readSize)
buf := make([]byte, len(zeroBlock))
for i := 0; i < loops; i++ {
if t.Failed() {
return
}
off := rand.Int63n(int64(fileSize - len(zeroBlock) - 1))
_, err := f.ReadAt(buf, off)
if err != nil {
t.Errorf("readThread iteration %d: ReadAt failed: %v", i, err)
return
}
if !bytes.Equal(buf, zeroBlock) {
t.Errorf("readThread iteration %d: data mismatch", i)
return
}
}
}
wg.Add(4)
go writeThread(f1)
go writeThread(f2)
go readThread(f1)
go readThread(f2)
wg.Wait()
}
// Multiple hosts creating the same file at the same time could
// overwrite each other's file header, leading to data
// corruption. Passing "-sharedstorage" should prevent this.
func TestConcurrentCreate(t *testing.T) {
cDir := test_helpers.InitFS(t)
mnt1 := cDir + ".mnt1"
mnt2 := cDir + ".mnt2"
test_helpers.MountOrFatal(t, cDir, mnt1, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt1)
test_helpers.MountOrFatal(t, cDir, mnt2, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt2)
var wg sync.WaitGroup
const loops = 10000
createOrOpen := func(path string) (f *os.File, err error) {
// Use the high-level os.Create/OpenFile instead of syscall.Open because we
// *want* Go's EINTR retry logic. glibc open(2) has similar logic.
f, err = os.OpenFile(path, os.O_CREATE|os.O_RDWR|os.O_EXCL, 0600)
if err == nil {
return
}
if !errors.Is(err, os.ErrExist) {
t.Logf("POSIX compliance issue: exclusive create failed with unexpected error: err=%v", errors.Unwrap(err))
}
f, err = os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
if err == nil {
return
}
t.Logf("POSIX compliance issue: non-exlusive create failed with err=%v", errors.Unwrap(err))
return
}
workerThread := func(path string) {
defer wg.Done()
buf := make([]byte, 10)
for i := 0; i < loops; i++ {
if t.Failed() {
return
}
f, err := createOrOpen(path)
if err != nil {
// retry
continue
}
defer f.Close()
_, err = f.WriteAt(buf, 0)
if err != nil {
t.Errorf("iteration %d: Pwrite: %v", i, err)
return
}
buf2 := make([]byte, len(buf)+1)
n, err := f.ReadAt(buf2, 0)
if err != nil && err != io.EOF {
t.Errorf("iteration %d: ReadAt: %v", i, err)
return
}
buf2 = buf2[:n]
if !bytes.Equal(buf, buf2) {
t.Errorf("iteration %d: corrupt data received: %x", i, buf2)
return
}
syscall.Unlink(path)
}
}
wg.Add(2)
go workerThread(mnt1 + "/foo")
go workerThread(mnt2 + "/foo")
wg.Wait()
}
func TestOpenTruncate(t *testing.T) {
cDir := test_helpers.InitFS(t)
mnt1 := cDir + ".mnt1"
mnt2 := cDir + ".mnt2"
test_helpers.MountOrFatal(t, cDir, mnt1, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt1)
test_helpers.MountOrFatal(t, cDir, mnt2, "-extpass=echo test", "-wpanic=0", "-sharedstorage")
defer test_helpers.UnmountPanic(mnt2)
var wg sync.WaitGroup
const loops = 100
writerThread := func(path string) {
defer wg.Done()
for i := 0; i < loops; i++ {
if t.Failed() {
return
}
f, err := os.Create(path)
if err != nil {
t.Logf("POSIX compliance issue: non-exlusive create failed with err=%v", errors.Unwrap(err))
continue
}
_, err = f.WriteAt([]byte("foo"), 0)
if err != nil {
t.Errorf("iteration %d: WriteAt: %v", i, err)
}
f.Close()
}
}
wg.Add(2)
go writerThread(mnt1 + "/foo")
go writerThread(mnt2 + "/foo")
wg.Wait()
}
|
