TestDiffDirChangeWithOverlayfs is failing (when TMPDIR is on tmpfs, not on ext4)

[AkihiroSuda]

Interesting; looks like this is failing on go1.22

cc @AkihiroSuda @dmcgowan

=== RUN   TestDiffDirChangeWithOverlayfs
    diff_test.go:249: failed diff dir change: Unexpected number of changes:
        got(6):
        	modify	/dir1
        	delete	/dir1/d
        	modify	/dir1/f
        	modify	/dir2/d/f
        	modify	/dir3
        	delete	/dir3/.wh..opq
        expected(8):
        	modify	/dir1
        	delete	/dir1/d
        	modify	/dir1/f
        	modify	/dir2
        	modify	/dir2/d
        	modify	/dir2/d/f
        	modify	/dir3
        	delete	/dir3/.wh..opq
--- FAIL: TestDiffDirChangeWithOverlayfs (0.01s)

Originally posted by @thaJeztah in #242 (comment)

(Unlikely specific to Go 1.22)

[AkihiroSuda]

Locally reproducible on Ubuntu 24.10 (kernel 6.11.0-9-generic #9-Ubuntu), but not reproducible on Ubuntu 24.04 (kernel 6.8.0-45-generic #45-Ubuntu) and Ubuntu 22.04 (kernel 5.15.0-122-generic #132-Ubuntu).

Not sure if this difference arises from the kernel version or some filesystem configuration.

[AkihiroSuda]

Looks like the test depends on the filesystem of TMPDIR, not on the kernel version.

Works with:

• /dev/vda1 on / type ext4 (rw,relatime,discard,errors=remount-ro,commit=30)

Fails with:

• tmpfs on /tmp type tmpfs (rw,nosuid,nodev,size=2003352k,nr_inodes=1048576,inode64)

[AkihiroSuda]

PR #249