Re: [LTP] [PATCH] unshare03: using soft limit of NOFILE

[Petr Vorel <pvorel@suse.cz>]

Hi lufei, Al,

@Al, you're the author of the original test unshare_test.c [1] in kselftest.
This is a patch to LTP test unshare03.c, which is based on your test.

> I think it's safer to set NOFILE increasing from soft limit than from
> hard limit.

> Hard limit may lead to dup2 ENOMEM error which bring the result to
> TBROK on little memory machine. (e.g. 2GB memory in my situation, hard
> limit in /proc/sys/fs/nr_open come out to be 1073741816)

IMHO lowering number to ~ half (in my case) by using rlimit.rlim_max instead of
/proc/sys/fs/nr_open should not affect the functionality of the test, right?
Or am I missing something obvious?

@lufei I guess kselftest tools/testing/selftests/core/unshare_test.c would fail
for you as well, right?

Kind regards,
Petr

[1] https://web.git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=611fbeb44a777e5ab54ab3127ec85f72147911d8

> Signed-off-by: lufei <lufei@uniontech.com>
> ---
>  testcases/kernel/syscalls/unshare/unshare03.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)

> diff --git a/testcases/kernel/syscalls/unshare/unshare03.c b/testcases/kernel/syscalls/unshare/unshare03.c
> index 7c5e71c4e..bb568264c 100644
> --- a/testcases/kernel/syscalls/unshare/unshare03.c
> +++ b/testcases/kernel/syscalls/unshare/unshare03.c
> @@ -24,7 +24,7 @@

>  static void run(void)
>  {
> -	int nr_open;
> +	int rlim_max;
>  	int nr_limit;
>  	struct rlimit rlimit;
>  	struct tst_clone_args args = {
> @@ -32,14 +32,12 @@ static void run(void)
>  		.exit_signal = SIGCHLD,
>  	};

> -	SAFE_FILE_SCANF(FS_NR_OPEN, "%d", &nr_open);
> -	tst_res(TDEBUG, "Maximum number of file descriptors: %d", nr_open);
> +	SAFE_GETRLIMIT(RLIMIT_NOFILE, &rlimit);
> +	rlim_max = rlimit.rlim_max;

> -	nr_limit = nr_open + NR_OPEN_LIMIT;
> +	nr_limit = rlim_max + NR_OPEN_LIMIT;
>  	SAFE_FILE_PRINTF(FS_NR_OPEN, "%d", nr_limit);

> -	SAFE_GETRLIMIT(RLIMIT_NOFILE, &rlimit);
> -
>  	rlimit.rlim_cur = nr_limit;
>  	rlimit.rlim_max = nr_limit;

> @@ -47,10 +45,10 @@ static void run(void)
>  	tst_res(TDEBUG, "Set new maximum number of file descriptors to : %d",
>  		nr_limit);

> -	SAFE_DUP2(2, nr_open + NR_OPEN_DUP);
> +	SAFE_DUP2(2, rlim_max + NR_OPEN_DUP);

>  	if (!SAFE_CLONE(&args)) {
> -		SAFE_FILE_PRINTF(FS_NR_OPEN, "%d", nr_open);
> +		SAFE_FILE_PRINTF(FS_NR_OPEN, "%d", rlim_max);
>  		TST_EXP_FAIL(unshare(CLONE_FILES), EMFILE);
>  		exit(0);
>  	}

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