Re: [PATCH] S390: Don't test nanoseconds in io/tst-stat.c

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 17/03/2021 10:03, Stefan Liebler wrote:
> Both new tests io/tst-stat and io/tst-stat-lfs (_FILE_OFFSET_BITS=64)
> are comparing the nanosecond fields with the statx result.  Unfortunately
> on s390(31bit) those fields are always zero if old KABI with non-LFS
> support is used.  With _FILE_OFFSET_BITS=64 stat is using statx internally.
> 
> As suggested by Adhemerval this patch disables the nanosecond check for
> s390(31bit).

LGTM, the fstatat call does not call statx and even for LFS that call statx
it might ended calling old stat syscall in the fallback part that does not

About the __ASSUME_STATX note Joseph has raised, I think we should add it
on Linux at least for fstatat64 implementation. However it does not really
help on the fstatat one.  I will try to spare some time to make fstatat.c
use statx as well, so we can tie the test to __ASSUME_STATX.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  io/tst-stat.c                      |  7 +++++--
>  support/Makefile                   |  1 +
>  support/support.h                  |  3 +++
>  support/support_stat_nanoseconds.c | 31 ++++++++++++++++++++++++++++++
>  4 files changed, 40 insertions(+), 2 deletions(-)
>  create mode 100644 support/support_stat_nanoseconds.c
> 
> diff --git a/io/tst-stat.c b/io/tst-stat.c
> index 445ac4176c..397d480ecc 100644
> --- a/io/tst-stat.c
> +++ b/io/tst-stat.c
> @@ -91,9 +91,12 @@ do_test (void)
>        TEST_COMPARE (stx.stx_blocks, st.st_blocks);
>  
>        TEST_COMPARE (stx.stx_ctime.tv_sec, st.st_ctim.tv_sec);
> -      TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
>        TEST_COMPARE (stx.stx_mtime.tv_sec, st.st_mtim.tv_sec);
> -      TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
> +      if (support_stat_nanoseconds ())
> +	{
> +	  TEST_COMPARE (stx.stx_ctime.tv_nsec, st.st_ctim.tv_nsec);
> +	  TEST_COMPARE (stx.stx_mtime.tv_nsec, st.st_mtim.tv_nsec);
> +	}
>      }
>  
>    return 0;
> diff --git a/support/Makefile b/support/Makefile
> index fc9f4936a8..900e17f94f 100644
> --- a/support/Makefile
> +++ b/support/Makefile
> @@ -71,6 +71,7 @@ libsupport-routines = \
>    support_set_small_thread_stack_size \
>    support_shared_allocate \
>    support_small_stack_thread_attribute \
> +  support_stat_nanoseconds \
>    support_subprocess \
>    support_test_compare_blob \
>    support_test_compare_failure \
> diff --git a/support/support.h b/support/support.h
> index 2e477c9e7c..90f3ff9d1a 100644
> --- a/support/support.h
> +++ b/support/support.h
> @@ -134,6 +134,9 @@ extern ssize_t support_copy_file_range (int, off64_t *, int, off64_t *,
>     operations (such as fstatat or utimensat).  */
>  extern bool support_path_support_time64 (const char *path);
>  
> +/* Return true if stat supports nanoseconds resolution.  */
> +extern bool support_stat_nanoseconds (void);
> +
>  __END_DECLS
>  
>  #endif /* SUPPORT_H */
> diff --git a/support/support_stat_nanoseconds.c b/support/support_stat_nanoseconds.c
> new file mode 100644
> index 0000000000..c0d5b2c3a9
> --- /dev/null
> +++ b/support/support_stat_nanoseconds.c
> @@ -0,0 +1,31 @@
> +/* Check if stat supports nanosecond resolution.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <stdbool.h>
> +
> +bool
> +support_stat_nanoseconds (void)
> +{
> +  /* s390 stat64 compat symbol does not support nanoseconds resolution
> +     and it used on non-LFS [f,l]stat[at] implementations.  */
> +#if defined __linux__ && !defined __s390x__ && defined __s390__
> +  return false;
> +#else
> +  return true;
> +#endif
> +}
>