[LTP] [PATCH 1/3] lib: introduce safe_write_fully()

[Jan Stancek]

On Mon, Oct 3, 2022 at 3:14 PM Cyril Hrubis <chrubis@suse.cz> wrote:
>
> Hi!
> > In case there is a short (but otherwise successful) write(),
> > safe_write_fully() repeats write() and attempts to resume
> > with the remainder of the buffer.
> >
> > Signed-off-by: Jan Stancek <jstancek@redhat.com>
> > ---
> >  include/tst_safe_macros.h |  5 +++++
> >  lib/tst_safe_macros.c     | 19 +++++++++++++++++++
> >  2 files changed, 24 insertions(+)
> >
> > diff --git a/include/tst_safe_macros.h b/include/tst_safe_macros.h
> > index 81c4b0844267..caee0e9cf842 100644
> > --- a/include/tst_safe_macros.h
> > +++ b/include/tst_safe_macros.h
> > @@ -645,4 +645,9 @@ int safe_sysinfo(const char *file, const int lineno, struct sysinfo *info);
> >  #define SAFE_SYSINFO(info) \
> >       safe_sysinfo(__FILE__, __LINE__, (info))
> >
> > +ssize_t safe_write_fully(const char *file, const int lineno,
> > +     int fildes, const void *buf, size_t nbyte);
> > +#define SAFE_WRITE_FULLY(fildes, buf, nbyte) \
> > +     safe_write_fully(__FILE__, __LINE__, (fildes), (buf), (nbyte))
>
> We already have a flag for SAFE_WRITE() to fail/not-fail on partial
> write, what about turning that into three way switch?
>
> Something as:
>
> enum safe_write_opts {
>         SAFE_WRITE_PARTIAL = 0,
>         SAFE_WRITE_FULL = 1,
>         SAFE_WRITE_RETRY = 2,
> };

I do find those names little confusing. What do you think about:

SAFE_WRITE_ANY = 0 // no strictness
SAFE_WRITE_ALL = 1 // all strict
SAFE_WRITE_RETRY = 2 // retry


>
> Or maybe just rename the SAFE_WRITE_FULLY() to SAFE_WRITE_RETRY().
>
> >  #endif /* SAFE_MACROS_H__ */
> > diff --git a/lib/tst_safe_macros.c b/lib/tst_safe_macros.c
> > index c4cdc87e7346..e4d4ef4269a4 100644
> > --- a/lib/tst_safe_macros.c
> > +++ b/lib/tst_safe_macros.c
> > @@ -591,3 +591,22 @@ void safe_cmd(const char *file, const int lineno, const char *const argv[],
> >               tst_brk_(file, lineno, TBROK, "%s failed (%d)", argv[0], rval);
> >       }
> >  }
> > +
> > +ssize_t safe_write_fully(const char *file, const int lineno,
> > +     int fildes, const void *buf, size_t nbyte)
> > +{
> > +     ssize_t rval;
> > +     size_t len = nbyte;
> > +
> > +     do {
> > +             rval = write(fildes, buf, len);
> > +             if (rval == -1) {
> > +                     tst_brk_(file, lineno, TBROK | TERRNO,
> > +                             "write(%d,%p,%zu) failed", fildes, buf, len);
>
> I guess that we may print potentionally confusing output here since we
> modify the buf and len in the loop. I guess that we should store the buf
> pointer at the start just for a case of this message and use the nbyte
> and possibly write how many bytes we have managed to write before the
> failure.

ack


>
> > +             }
> > +             buf += rval;
> > +             len -= rval;
> > +     } while (len > 0);
> > +
> > +     return nbyte;
> > +}
> > --
> > 2.27.0
> >
> >
> > --
> > Mailing list info: https://lists.linux.it/listinfo/ltp
>
> --
> Cyril Hrubis
> chrubis@suse.cz
>