From 772032598a4282a50ccee29e9cc23be88bd74b2f Mon Sep 17 00:00:00 2001
From: Derek McGowan <derek@mcgstyle.net>
Date: Fri, 4 Oct 2019 17:51:45 -0700
Subject: [PATCH] Fix flaky btrfs test

Add logging and move the creation of the snapshotter inside
the attempt loop to catch cases where the mountinfo may
not be updated yet. When all attempts are reached there
is no reason to create the snapshotter as the unmount has
already occurred.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>
---
 snapshots/btrfs/btrfs.go      |  2 +-
 snapshots/btrfs/btrfs_test.go | 25 +++++++++++++++----------
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/snapshots/btrfs/btrfs.go b/snapshots/btrfs/btrfs.go
index 540601d93..5abe9c064 100644
--- a/snapshots/btrfs/btrfs.go
+++ b/snapshots/btrfs/btrfs.go
@@ -77,7 +77,7 @@ func NewSnapshotter(root string) (snapshots.Snapshotter, error) {
 		return nil, err
 	}
 	if mnt.FSType != "btrfs" {
-		return nil, errors.Wrapf(plugin.ErrSkipPlugin, "path %s must be a btrfs filesystem to be used with the btrfs snapshotter", root)
+		return nil, errors.Wrapf(plugin.ErrSkipPlugin, "path %s (%s) must be a btrfs filesystem to be used with the btrfs snapshotter", root, mnt.FSType)
 	}
 	var (
 		active    = filepath.Join(root, "active")
diff --git a/snapshots/btrfs/btrfs_test.go b/snapshots/btrfs/btrfs_test.go
index 5322f261f..8e457ec76 100644
--- a/snapshots/btrfs/btrfs_test.go
+++ b/snapshots/btrfs/btrfs_test.go
@@ -30,6 +30,7 @@ import (
 
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/pkg/testutil"
+	"github.com/containerd/containerd/plugin"
 	"github.com/containerd/containerd/snapshots"
 	"github.com/containerd/containerd/snapshots/testsuite"
 	"github.com/containerd/continuity/testutil/loopback"
@@ -66,27 +67,31 @@ func boltSnapshotter(t *testing.T) func(context.Context, string) (snapshots.Snap
 		// sync after a mkfs on the loopback before trying to mount the device
 		unix.Sync()
 
+		var snapshotter snapshots.Snapshotter
 		for i := 0; i < 5; i++ {
 			if out, err := exec.Command("mount", loop.Device, root).CombinedOutput(); err != nil {
 				loop.Close()
 				return nil, nil, errors.Wrapf(err, "failed to mount device %s (out: %q)", loop.Device, out)
 			}
-			var stat unix.Statfs_t
-			if err := unix.Statfs(root, &stat); err != nil {
-				unix.Unmount(root, 0)
-				return nil, nil, errors.Wrapf(err, "unable to statfs btrfs mount %s", root)
+
+			if i > 0 {
+				time.Sleep(10 * time.Duration(i) * time.Millisecond)
 			}
-			if stat.Type == unix.BTRFS_SUPER_MAGIC {
+
+			snapshotter, err = NewSnapshotter(root)
+			if err == nil {
 				break
+			} else if errors.Cause(err) != plugin.ErrSkipPlugin {
+				return nil, nil, err
 			}
+
+			t.Logf("Attempt %d to create btrfs snapshotter failed: %#v", i+1, err)
+
 			// unmount and try again
 			unix.Unmount(root, 0)
-			time.Sleep(100 * time.Millisecond)
 		}
-		snapshotter, err := NewSnapshotter(root)
-		if err != nil {
-			loop.Close()
-			return nil, nil, errors.Wrap(err, "failed to create new snapshotter")
+		if snapshotter == nil {
+			return nil, nil, errors.Wrap(err, "failed to successfully create snapshotter after 5 attempts")
 		}
 
 		return snapshotter, func() error {