[LTP] [RFC PATCH] copy_file_range03: comparing timestamp with tst_timespec_diff

[Li Wang]

[Cc Amir, Thomas if they have better advice on this]

On Thu, Sep 2, 2021 at 6:46 PM Li Wang <liwang@redhat.com> wrote:

> The st_mtime field is defined as st_mtim.tv_sec for backward
> compatibility in struct stat, which might not precise enough
> for timestamp comparing.
>
> Similar issue as:
>   https://lists.linux.it/pipermail/ltp/2020-November/019982.html
>
> Here switch to timespec diff (with compare nanosecond as well) to
> get rid of this kind of rare faliure:
>
>    7    tst_test.c:1345: TINFO: Timeout per run is 0h 05m 00s
>    8    copy_file_range.h:36: TINFO: Testing libc copy_file_range()
>    9    copy_file_range03.c:48: TPASS: copy_file_range sucessfully updated
> the timestamp
>    10   tst_test.c:1345: TINFO: Timeout per run is 0h 05m 00s
>    11   copy_file_range.h:39: TINFO: Testing __NR_copy_file_range syscall
>    12   copy_file_range03.c:46: TFAIL: copy_file_range did not update
> timestamp.
>

After digging into syscall copy_file_range (which mainly call
the splice_direct_to_actor), I found it relies on the specific
filesystem (my platform is XFS) to complete the timestamps
updating.

For XFS, the “file_modified“ code path is via
file_update_time() --> current_time() --> timestamp_truncate()
to get a truncated current time for use.

Then, I guess, there is also potential to get a round-down value,
then apply it to the dest_file as timestamp, reflect to the userland,
it shows time no change in 1 second elapsed.

So another improvement is to let it wait a bit more than 1 second
to counteract the rounded-down nanosecond.

I'd add the below change in the patch V2 to make the test more robust.

--- a/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
+++ b/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
@@ -32,7 +32,7 @@ static void verify_copy_file_range_timestamp(void)
        struct timespec timestamp1, timestamp2, diff;

        timestamp1 = get_timestamp(fd_dest);
-       usleep(1000000);
+       usleep(1500000);

        offset = 0;
        TEST(sys_copy_file_range(fd_src, &offset,


>
> Signed-off-by: Li Wang <liwang@redhat.com>
> ---
>  .../syscalls/copy_file_range/copy_file_range03.c  | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
> b/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
> index 253eb57ad..5d055e6ba 100644
> --- a/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
> +++ b/testcases/kernel/syscalls/copy_file_range/copy_file_range03.c
> @@ -12,25 +12,26 @@
>  #define _GNU_SOURCE
>
>  #include "tst_test.h"
> +#include "tst_timer.h"
>  #include "copy_file_range.h"
>
>  static int fd_src;
>  static int fd_dest;
>
> -unsigned long get_timestamp(int fd)
> +struct timespec get_timestamp(int fd)
>  {
>         struct stat filestat;
>
>         fstat(fd, &filestat);
> -       return filestat.st_mtime;
> +       return filestat.st_mtim;
>  }
>
>  static void verify_copy_file_range_timestamp(void)
>  {
>         loff_t offset;
> -       unsigned long timestamp, updated_timestamp;
> +       struct timespec timestamp1, timestamp2, diff;
>
> -       timestamp = get_timestamp(fd_dest);
> +       timestamp1 = get_timestamp(fd_dest);
>         usleep(1000000);
>
>         offset = 0;
> @@ -40,9 +41,11 @@ static void verify_copy_file_range_timestamp(void)
>                 tst_brk(TBROK | TTERRNO,
>                                 "copy_file_range unexpectedly failed");
>
> -       updated_timestamp = get_timestamp(fd_dest);
> +       timestamp2 = get_timestamp(fd_dest);
>
> -       if (timestamp == updated_timestamp)
> +       diff = tst_timespec_diff(timestamp1, timestamp2);
> +
> +       if (!diff.tv_sec && !diff.tv_nsec)
>                 tst_brk(TFAIL, "copy_file_range did not update
> timestamp.");
>
>         tst_res(TPASS, "copy_file_range sucessfully updated the
> timestamp");
> --
> 2.31.1
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>
>

-- 
Regards,
Li Wang
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