Re: [PATCH v3 0/6] selftests/liveupdate: add memfd tests

[Pasha Tatashin <pasha.tatashin@soleen.com>]

On 04-04 10:24, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> Hi,
> 
> This series adds some tests for memfd preservation across a live update.
> Currently memfd is only tested indirectly via luo_kexec_simple or
> luo_multi_session. Add a dedicated test suite for it.
> 
> Patches 1 and 2 are preparatory, adding base framework and helpers, and
> the other patches each add a test. Some of the code is taken from the
> libluo patches [0] I sent a while ago.
> 
> [0] https://lore.kernel.org/linux-mm/20250723144649.1696299-33-pasha.tatashin@soleen.com/

Here are few observations that I noticed when I tried to run your tests:

1. The '-h' tells you nothing about --stage argument:

root@liveupdate-vm:~/liveupdate# ./luo_memfd -h
Usage: ./luo_memfd [-h|-l|-d] [-t|-T|-v|-V|-f|-F|-r name]
	-h       print help
	-l       list all tests
	-d       enable debug prints

	-t name  include test
	-T name  exclude test
	-v name  include variant
	-V name  exclude variant
	-f name  include fixture
	-F name  exclude fixture
	-r name  run specified test
	...

2. '-l' does not work after you run stage1, do you keep /dev/liveupdate 
open? That is not needed, we only need to keep session open.

root@liveupdate-vm:~/liveupdate# ./luo_memfd -l
1..0 # SKIP Failed to open /dev/liveupdate (Device or resource busy) device. Is LUO enabled?

3. Stage 1 has proper [STAGE 1] prefix, but no [STAGE 2] prefix for 
stage 2:
# Starting 4 tests from 1 test cases.
#  RUN           global.memfd_data ...
# [STAGE 1] Forking persistent child to hold sessions...
# [STAGE 1] Child PID: 245. Resources are pinned.
# [STAGE 1] You may now perform kexec reboot.
#            OK  global.memfd_data
ok 1 global.memfd_data
#  RUN           global.zero_memfd ...
# [STAGE 1] Forking persistent child to hold sessions...
# [STAGE 1] Child PID: 247. Resources are pinned.
# [STAGE 1] You may now perform kexec reboot.
#            OK  global.zero_memfd
ok 2 global.zero_memfd
#  RUN           global.preserved_ops ...
#            OK  global.preserved_ops
ok 3 global.preserved_ops
#  RUN           global.fallocate_memfd ...
# [STAGE 1] Forking persistent child to hold sessions...
# [STAGE 1] Child PID: 250. Resources are pinned.
# [STAGE 1] You may now perform kexec reboot.
#            OK  global.fallocate_memfd
ok 4 global.fallocate_memfd
# PASSED: 4 / 4 tests passed.
# Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0

./do_kexec

root@liveupdate-vm:~/liveupdate# ./luo_memfd
TAP version 13
1..4
# Starting 4 tests from 1 test cases.
#  RUN           global.memfd_data ...
#            OK  global.memfd_data
ok 1 global.memfd_data
#  RUN           global.zero_memfd ...
#            OK  global.zero_memfd
ok 2 global.zero_memfd
#  RUN           global.preserved_ops ...
#      SKIP      test only expected to run on stage 1
#            OK  global.preserved_ops
ok 3 global.preserved_ops # SKIP test only expected to run on stage 1
#  RUN           global.fallocate_memfd ...
#            OK  global.fallocate_memfd
ok 4 global.fallocate_memfd
# PASSED: 4 / 4 tests passed.
# 1 skipped test(s) detected. Consider enabling relevant config options to improve coverage.
# Totals: pass:3 fail:0 xfail:0 xpass:0 skip:1 error:0

4. I also do not like that we now have duplicated stage parsing code in  
luo_test(), perhaps we should add our own  test_harness_run() variant 
that depends on stage, and use it in both current tests, and the new 
memfd tests.

Pasha

> 
> Changes in v3:
> - Retry on EINTR instead of giving up in read_size() and write_size().
> - Use O_TRUNC in save_test_data().
> - Return the value of write_size() directly in create_random_memfd(). No
>   need to check errno since write_size() already returns -errno.
> - Save errno before calling close() in create_random_memfd() to avoid
>   overwriting the value.
> - Use memcmp() instead of open-coding the comparison loop.
> - Return value of test_harness_run() from main().
> 
> Changes in v2:
> - Drop LIVEUPDATE_DEV since it isn't used.
> - Split luo_fd and stage declaration on separate lines.
> - Split all 2-stage tests into helper function for each test.
> - Fix wording and argument order when LUO_DEVICE fails to open.
> - Rename verify_fd_content() to verify_fd_content_read().
> - Advance buffer pointer in {read,write}_size().
> - Add a check to make sure current working directory is not on a tmpfs
>   mount. If so, skip the tests since saved data files will be lost.
> - Rename RANDOM_DATA_FILE and RANDOM_DATA_FILE_FALLOCATE to
>   MEMFD_DATA_FS_COPY and FALLOCATE_DATA_FS_COPY respectively. Also
>   update the file names to reflect this naming convention.
> - Collect R-bys.
> 
> Regards,
> Pratyush Yadav
> 
> Pratyush Yadav (Google) (6):
>   selftests/liveupdate: add framework for memfd tests
>   selftests/liveupdate: add helper functions for memfd tests
>   selftests/liveupdate: add test for memfd content preservation
>   selftests/liveupdate: add test for zero-size memfd preservation
>   selftests/liveupdate: add test for operations on a preserved memfd
>   selftests/liveupdate: add fallocate test for memfd
> 
>  tools/testing/selftests/liveupdate/Makefile   |   2 +
>  .../testing/selftests/liveupdate/luo_memfd.c  | 355 ++++++++++++++++++
>  .../selftests/liveupdate/luo_test_utils.c     | 191 +++++++++-
>  .../selftests/liveupdate/luo_test_utils.h     |  10 +
>  4 files changed, 557 insertions(+), 1 deletion(-)
>  create mode 100644 tools/testing/selftests/liveupdate/luo_memfd.c
> 
> 
> base-commit: 98ddd87f9704ef2fc837ec2ca38877c364d8dada
> -- 
> 2.53.0.1213.gd9a14994de-goog
>