Re: [PATCH v11 5/9] Reimplement RLIMIT_MSGQUEUE on top of ucounts

[Alexey Gladkov <legion@kernel.org>]

On Tue, Aug 17, 2021 at 10:47:14AM -0500, Eric W. Biederman wrote:
> "Ma, XinjianX" <xinjianx.ma@intel.com> writes:
> 
> > Hi Alexey,
> >
> > When lkp team run kernel selftests, we found after these series of patches, testcase mqueue: mq_perf_tests
> > in kselftest failed with following message.
> 
> Which kernel was this run against?
> 
> Where can the mq_perf_tests that you ran and had problems with be found?
> 
> During your run were you using user namespaces as part of your test
> environment?
> 
> The error message too many files corresponds to the error code EMFILES
> which is the error code that is returned when the rlimit is reached.
> 
> One possibility is that your test environment was run in a user
> namespace and so you wound up limited by rlimit of the user who created
> the user namespace at the point of user namespace creation. 
> 
> At this point if you can give us enough information to look into this
> and attempt to reproduce it that would be appreciated.

I was able to reproduce it on master without using user namespace.
I suspect that the maximum value is not assigned here [1]:

set_rlimit_ucount_max(&init_user_ns, UCOUNT_RLIMIT_MSGQUEUE, task_rlimit(&init_task, RLIMIT_MSGQUEUE));

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/fork.c#n832

> > If you confirm and fix the issue, kindly add following tag as appropriate
> > Reported-by: kernel test robot lkp@intel.com
> >
> > ```
> > # selftests: mqueue: mq_perf_tests
> > #
> > # Initial system state:
> > #       Using queue path:                       /mq_perf_tests
> > #       RLIMIT_MSGQUEUE(soft):                  819200
> > #       RLIMIT_MSGQUEUE(hard):                  819200
> > #       Maximum Message Size:                   8192
> > #       Maximum Queue Size:                     10
> > #       Nice value:                             0
> > #
> > # Adjusted system state for testing:
> > #       RLIMIT_MSGQUEUE(soft):                  (unlimited)
> > #       RLIMIT_MSGQUEUE(hard):                  (unlimited)
> > #       Maximum Message Size:                   16777216
> > #       Maximum Queue Size:                     65530
> > #       Nice value:                             -20
> > #       Continuous mode:                        (disabled)
> > #       CPUs to pin:                            3
> > # ./mq_perf_tests: mq_open() at 296: Too many open files
> > not ok 2 selftests: mqueue: mq_perf_tests # exit=1
> > ```    
> >
> > Test env:
> > rootfs: debian-10
> > gcc version: 9
> >
> > ------
> > Thanks 
> > Ma Xinjian
> 
> Eric
> 

-- 
Rgrds, legion