[LTP] [PATCH v2 1/1] lib: Retry safe_clone() on ENOSPC|EUSERS

[Cyril Hrubis]

Hi!
> In some tests we are creating the namespaces faster than they are being
> asynchronously cleaned up in the kernel:
> 
> $ sudo ./userns08 -i 10
> userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
> userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
> userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
> userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
> userns08.c:65: TPASS: Denied write access to ./restricted : EACCES (13)
> userns08.c:36: TBROK: clone3 failed: ENOSPC (28)
> 
> Thus retrying the clone() on ENOSPC (or EUSERS for kernel < 4.9).
> 
> Suggested-by: Cyril Hrubis <chrubis@suse.cz>
> Signed-off-by: Petr Vorel <pvorel@suse.cz>
> ---
> changes v1->v2:
> * use TST_RETRY_FN_EXP_BACKOFF() (Cyril)
> 
> NOTE: 0.1s seems to be safe, although using TST_RETRY_FUNC() with 1s
> (the default) would be of course OK.

I would just put in the default 1s to make things extra safe even on
slow hardware.

>  lib/tst_test.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/tst_test.c b/lib/tst_test.c
> index 384c73e163..2e89d954ec 100644
> --- a/lib/tst_test.c
> +++ b/lib/tst_test.c
> @@ -436,6 +436,9 @@ pid_t safe_fork(const char *filename, unsigned int lineno)
>  	return pid;
>  }
>  
> +/* too fast creating namespaces => retrying */
> +#define TST_CHECK_ENOSPC(x) ((x) >= 0 || !(errno == ENOSPC || errno == EUSERS))

Reading the manual page I do not think that we have to retry on EUSERS,
that used to be the return value where we reached limit of nested
namespaces and that is not going go away if we retry.

Otherwise the rest looks good.

>  pid_t safe_clone(const char *file, const int lineno,
>  		 const struct tst_clone_args *args)
>  {
> @@ -444,7 +447,7 @@ pid_t safe_clone(const char *file, const int lineno,
>  	if (!tst_test->forks_child)
>  		tst_brk(TBROK, "test.forks_child must be set!");
>  
> -	pid = tst_clone(args);
> +	pid = TST_RETRY_FN_EXP_BACKOFF(tst_clone(args), TST_CHECK_ENOSPC, 0.1);
>  
>  	switch (pid) {
>  	case -1:

-- 
Cyril Hrubis
chrubis@suse.cz