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authorJakob Unterwurzacher2023-05-30 09:43:45 +0200
committerJakob Unterwurzacher2023-05-30 09:43:45 +0200
commit3058b7978fd8dabd3e8565c9be816b1367bd196a (patch)
tree189b177c234bc5950bd68efac08e65eec82a5e9c /tests
parentb725de5ec300aec208908c6a3bf5443cee7cfa81 (diff)
tests: add 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.
Diffstat (limited to 'tests')
-rw-r--r--tests/cluster/cluster_test.go111
1 files changed, 111 insertions, 0 deletions
diff --git a/tests/cluster/cluster_test.go b/tests/cluster/cluster_test.go
new file mode 100644
index 0000000..2e969ce
--- /dev/null
+++ b/tests/cluster/cluster_test.go
@@ -0,0 +1,111 @@
+// 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"
+ "math/rand"
+ "os"
+ "sync"
+ "testing"
+
+ "github.com/rfjakob/gocryptfs/v2/tests/test_helpers"
+)
+
+// This test 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.
+// > This behavior is unique to XFS on Linux and is not optional.
+// > Other Linux filesystems only guaranty page level atomicity for
+// > buffered read/write.
+//
+// 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) {
+ if os.Getenv("ENABLE_CLUSTER_TEST") != "1" {
+ t.Skipf("This test is disabled by default because it fails unless on XFS.\n" +
+ "Run it like this: ENABLE_CLUSTER_TEST=1 go test\n" +
+ "Choose a backing directory by setting TMPDIR.")
+ }
+
+ const blocksize = 4096
+ const fileSize = 25 * blocksize // 100 kiB
+
+ cDir := test_helpers.InitFS(t)
+ mnt1 := cDir + ".mnt1"
+ mnt2 := cDir + ".mnt2"
+ test_helpers.MountOrFatal(t, cDir, mnt1, "-extpass=echo test", "-wpanic=0")
+ defer test_helpers.UnmountPanic(mnt1)
+ test_helpers.MountOrFatal(t, cDir, mnt2, "-extpass=echo test", "-wpanic=0")
+ 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, blocksize)
+ for i := 0; i < loops; i++ {
+ if t.Failed() {
+ return
+ }
+ off := rand.Int63n(fileSize / blocksize)
+ _, 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, blocksize)
+ buf := make([]byte, blocksize)
+ for i := 0; i < loops; i++ {
+ if t.Failed() {
+ return
+ }
+ off := rand.Int63n(fileSize / blocksize)
+ _, 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()
+}