Re: [PATCH 16/18] linux: Only use 64-bit syscall if required for utimensat family

[Lukasz Majewski <lukma@denx.de>]

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On Thu, 17 Jun 2021 08:51:02 -0300
Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> For !__ASSUME_TIME64_SYSCALLS there is no need to issue a 64-bit
> syscall if the provided timeout fits in a 32-bit one.  The 64-bit
> usage should be rare since the timeout is a relative one.
> 
> The large timeout are already tests by io/tst-utimensat-skeleton.c.
> 
> Checked on i686-linux-gnu on a 4.15 kernel and on a 5.11 kernel
> (with and without --enable-kernel=5.1) and on x86_64-linux-gnu.
> ---
>  sysdeps/unix/sysv/linux/utimensat.c | 35
> ++++++++++++++++++----------- 1 file changed, 22 insertions(+), 13
> deletions(-)
> 
> diff --git a/sysdeps/unix/sysv/linux/utimensat.c
> b/sysdeps/unix/sysv/linux/utimensat.c index 909a29762b..e79e4351d6
> 100644 --- a/sysdeps/unix/sysv/linux/utimensat.c
> +++ b/sysdeps/unix/sysv/linux/utimensat.c
> @@ -31,34 +31,43 @@ __utimensat64_helper (int fd, const char *file,
>  #ifndef __NR_utimensat_time64
>  # define __NR_utimensat_time64 __NR_utimensat
>  #endif
> -  int ret = INLINE_SYSCALL_CALL (utimensat_time64, fd, file,
> &tsp64[0], flags); -#ifndef __ASSUME_TIME64_SYSCALLS
> -  if (ret == 0 || errno != ENOSYS)
> -    return ret;
>  
> +#ifdef __ASSUME_TIME64_SYSCALLS
> +  return INLINE_SYSCALL_CALL (utimensat_time64, fd, file, &tsp64[0],
> flags); +#else
>    /* For UTIME_NOW and UTIME_OMIT the value of tv_sec field is
> ignored.  */ -# define TS_VALID(ns) \
> -  ((((ns).tv_nsec == UTIME_NOW || (ns).tv_nsec == UTIME_OMIT) \
> -   || in_time_t_range ((ns).tv_sec)))
> +# define TS_SPECIAL(ts) \
> +  ((ts).tv_nsec == UTIME_NOW || (ts).tv_nsec == UTIME_OMIT)
>  
> -  if (tsp64 != NULL
> -      && (!TS_VALID (tsp64[0]) || !TS_VALID (tsp64[1])))
> +  bool is32bit_t0 = tsp64 != NULL
> +		    ? TS_SPECIAL (tsp64[0])
> +		      || in_time_t_range (tsp64[0].tv_sec)
> +	            : true;
> +  bool is32bit_t1 = tsp64 != NULL
> +		    ? TS_SPECIAL (tsp64[1])
> +		      || in_time_t_range (tsp64[1].tv_sec)
> +	            : true;
> +
> +  if (!is32bit_t0 || !is32bit_t1)
>      {
> +      int r = INLINE_SYSCALL_CALL (utimensat_time64, fd, file,
> &tsp64[0],
> +				   flags);
> +      if (r == 0 || errno != ENOSYS)
> +	return r;
>        __set_errno (EOVERFLOW);
>        return -1;
>      }
>  
> -  struct timespec tsp32[2];
> +  struct timespec tsp32[2], *ptsp32 = NULL;
>    if (tsp64)
>      {
>        tsp32[0] = valid_timespec64_to_timespec (tsp64[0]);
>        tsp32[1] = valid_timespec64_to_timespec (tsp64[1]);
> +      ptsp32 = tsp32;
>      }
>  
> -  ret = INLINE_SYSCALL_CALL (utimensat, fd, file, tsp64 ? &tsp32[0]
> : NULL,
> -			     flags);
> +  return INLINE_SYSCALL_CALL (utimensat, fd, file, ptsp32, flags);
>  #endif
> -  return ret;
>  }
>  libc_hidden_def (__utimensat64_helper)
>  

Reviewed-by: Lukasz Majewski <lukma@denx.de>


Best regards,

Lukasz Majewski

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