Re: [PATCH 2/2] selftests/filesystems/openat2: make /tmp a mountpoint inside private namespace

[andy_gao]

Hi Disha,

Tested patch 2/2 on 22 September 2026 on x86_64 with Linux 7.3-rc4,
using base commit
93f51579e7df248780214094418f205253383cc5.

Environment:
- QEMU 6.2.0 with TCG, 2 vCPUs and 2 GiB RAM, via virtme-ng 1.41.
- Guest kernel: 7.3.0-rc4-virtme; Ubuntu 22.04 userspace.
- GCC 11.4.0; resolve_test built with the upstream Makefile, retaining
  -fsanitize=address -fsanitize=undefined and -static-libasan.

I ran the unmodified and patched resolve_test on the same guest kernel.
A temporary tmpfs-backed chroot in a private mount namespace provided
two /tmp layouts: an ordinary writable directory and a separate tmpfs
mount. /proc was mounted in the chroot and /dev/null was available.

Results for all five resolve_test harness tests:

  /tmp layout            Unmodified          Patch 2/2 applied
  ordinary directory     0 pass, 5 fail       5 pass, 0 fail
  separate tmpfs mount   5 pass, 0 fail       5 pass, 0 fail

There were no skipped tests in any run. With an ordinary /tmp directory,
all five unmodified tests failed at the fixture setup assertion for
mount("", "/tmp", "", MS_PRIVATE, ""). With the patch, all five passed,
including resolve_no_xdev. The existing mountpoint layout also continued
to pass.

Only patch 2/2 was tested; this does not cover the architecture-specific
O_LARGEFILE changes in patch 1/2.

Tested-by: andy_gao <andy23320@xxxxxxxxx>

Thanks,
andy_gao