Re: [PATCH 3/3] printk: dump full information of page flags in pGp

[Yafang Shao <laoar.shao@gmail.com>]

On Thu, Jan 28, 2021 at 10:52 AM Miaohe Lin <linmiaohe@huawei.com> wrote:
>
> Hi:
> On 2021/1/28 10:19, Yafang Shao wrote:
> > Currently the pGp only shows the names of page flags, rather than
> > the full information including section, node, zone, last cpupid and
> > kasan tag. While it is not easy to parse these information manually
> > because there're so many flavors. Let's interpret them in pGp as well.
> >
> > - Before the patch,
> > [ 6312.639698] ERR: Slab 0x000000006d1133b9 objects=33 used=3 fp=0x000000006d0779d1 flags=0x17ffffc0010200(slab|head)
> >
> > - After the patch,
> > [ 6315.235783] ERR: Slab 0x000000006d1133b9 objects=33 used=3 fp=0x000000006d0779d1 flags=0x17ffffc0010200(Node 0x0,Zone 0x2,Lastcpupid 0x1fffff,slab|head)
> >
>
> Thanks. This really helps!
>
> > Cc: David Hildenbrand <david@redhat.com>
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > ---
> >  lib/vsprintf.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 41 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> > index 3b53c73580c5..bd809f4f1b82 100644
> > --- a/lib/vsprintf.c
> > +++ b/lib/vsprintf.c
> > @@ -1916,6 +1916,46 @@ char *format_flags(char *buf, char *end, unsigned long flags,
> >       return buf;
> >  }
> >
> > +struct page_flags_layout {
> > +     int width;
> > +     int shift;
> > +     int mask;
> > +     char *name;
>
> Should we add const for name ?
>

Good suggestion.

> > +};
> > +
> > +struct page_flags_layout pfl[] = {
>
> Should we add static const for pfl[] as we won't change its value and use it outside this file ?
>

Sure.

> > +     {SECTIONS_WIDTH, SECTIONS_PGSHIFT, SECTIONS_MASK, "Section "},
> > +     {NODES_WIDTH, NODES_PGSHIFT, NODES_MASK, "Node "},
> > +     {ZONES_WIDTH, ZONES_PGSHIFT, ZONES_MASK, "Zone "},
> > +     {LAST_CPUPID_WIDTH, LAST_CPUPID_PGSHIFT, LAST_CPUPID_MASK, "Lastcpupid "},
> > +     {KASAN_TAG_WIDTH, KASAN_TAG_PGSHIFT, KASAN_TAG_MASK, "Kasantag "},
> > +};
> > +
> > +static
> > +char *format_layout(char *buf, char *end, unsigned long flags)
> > +{
> > +     int i;
> > +
> > +     for (i = 0; i < sizeof(pfl) / sizeof(struct page_flags_layout) && buf < end; i++) {
>
> I think we can use ARRAY_SIZE here.
>

Sure.

> > +             if (pfl[i].width == 0)
> > +                     continue;
> > +
> > +             buf = string(buf, end, pfl[i].name, default_str_spec);
> > +
> > +             if (buf >= end)
> > +                     break;
> > +             buf = number(buf, end, (flags >> pfl[i].shift) & pfl[i].mask,
> > +                          default_flag_spec);
> > +
> > +             if (buf >= end)
> > +                     break;
> > +             *buf = ',';
> > +             buf++;
> > +     }
> > +
> > +     return buf;
> > +}
> > +
> >  static noinline_for_stack
> >  char *flags_string(char *buf, char *end, void *flags_ptr,
> >                  struct printf_spec spec, const char *fmt)
> > @@ -1929,7 +1969,7 @@ char *flags_string(char *buf, char *end, void *flags_ptr,
> >       switch (fmt[1]) {
> >       case 'p':
> >               flags = *(unsigned long *)flags_ptr;
> > -             /* Remove zone id */
> > +             buf = format_layout(buf, end, flags & ~((1UL << NR_PAGEFLAGS) - 1));
> >               flags &= (1UL << NR_PAGEFLAGS) - 1;
> >               names = pageflag_names;
> >               break;
> >
> Many thanks.



-- 
Thanks
Yafang