Re: [LTP] [PATCH] mount03: flip to the next second before doing the access

["xuyang2018.jy@fujitsu.com" <xuyang2018.jy@fujitsu.com>]

Hi Li

Looks good to me,
Reviewed-by: Yang Xu <xuyang2018.jy@fujitsu.com>

Best Regards
Yang Xu
> Mount03 occasionally reports failure on tmpfs:
> 
>    170	mount03.c:214: TINFO: Testing flag MS_STRICTATIME
>    171	mount03.c:140: TFAIL: st.st_atime(1677086243) < atime(1677086243)
>    172	mount03.c:151: TFAIL: dir_st.st_atime(1677086243) < dir_atime(1677086243)
> 
>  From Waiman Long:
> 
>    Looking at the mount03.c test, it is reading a directory in tmpfs, sleeping for
>    1 second and read the directory again. The test fails because the reported atime
>    didn't change. Since tmpfs is in memory, access to them can be much faster and I
>    believe that a race condition may happen that the two directory reads can happen
>    within the same atime even though one second is supposed to have passed. The same
>    test pass when applying to a real filesystem. So I believe the assumption made in
>    the test may not be totally correct as the time lag can happen in different
>    subsystems inside the kernel for time tracking. I believe it is more a test problem
>    than a real kernel problem.
> 
>    There may be some slight discrepancy in how sleep and the tmpfs file system is
>    keeping track of time. If the first access is right at the beginning of a second
>    from the tmpfs perspective, the 2nd access may be at the end of that second, but
>    not flip to the next second yet. What I would suggest is to sleep a little more
>    like usleep(10 000) to make sure that it will flip to the next second before doing
>    the access.
> 
> Suggested-by: Waiman Long <llong@redhat.com>
> Signed-off-by: Li Wang <liwang@redhat.com>
> ---
>   testcases/kernel/syscalls/mount/mount03.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/testcases/kernel/syscalls/mount/mount03.c b/testcases/kernel/syscalls/mount/mount03.c
> index 60f9963da..98d5933b7 100644
> --- a/testcases/kernel/syscalls/mount/mount03.c
> +++ b/testcases/kernel/syscalls/mount/mount03.c
> @@ -122,7 +122,7 @@ static void test_file_dir_noatime(int update_fatime, int update_datime)
>   	SAFE_CLOSEDIR(test_dir);
>   	dir_atime = dir_st.st_atime;
>   
> -	sleep(1);
> +	usleep(1001000);
>   
>   	SAFE_READ(0, otfd, readbuf, sizeof(readbuf));
>   	SAFE_FSTAT(otfd, &st);

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