On Tue 07-11-17 07:34:25, Joe Perches wrote:
> On Tue, 2017-11-07 at 13:50 +0100, Michal Hocko wrote:
> > On Mon 06-11-17 10:02:56, Joe Perches wrote:
> > > KERN_CONT/pr_cont uses should be avoided where possible.
> > > Use single pr_warn calls instead.
> []
> > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> []
> > > @@ -3275,19 +3275,17 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...)
> > > if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs))
> > > return;
> > >
> > > - pr_warn("%s: ", current->comm);
> > > -
> > > va_start(args, fmt);
> > > vaf.fmt = fmt;
> > > vaf.va = &args;
> > > - pr_cont("%pV", &vaf);
> > > - va_end(args);
> > > -
> > > - pr_cont(", mode:%#x(%pGg), nodemask=", gfp_mask, &gfp_mask);
> > > if (nodemask)
> > > - pr_cont("%*pbl\n", nodemask_pr_args(nodemask));
> > > + pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=%*pbl\n",
> > > + current->comm, &vaf, gfp_mask, &gfp_mask,
> > > + nodemask_pr_args(nodemask));
> > > else
> > > - pr_cont("(null)\n");
> > > + pr_warn("%s: %pV, mode:%#x(%pGg), nodemask=(null)\n",
> > > + current->comm, &vaf, gfp_mask, &gfp_mask);
> > > + va_end(args);
> > >
> > > cpuset_print_current_mems_allowed();
> >
> > I do not like the duplication. It just calls for inconsistencies over
> > time. Can we instead make %*pbl consume NULL nodemask instead?
> > Something like the following pseudo patch + the if/else removed.
> > If this would be possible we could simplify other code as well I think
> > (at least oom code has to special case NULL nodemask).
> >
> > What do you think?
>
> I think it would be fine to have a single pr_warn.
>
> > ---
> > diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> []
> > @@ -104,7 +104,7 @@ extern nodemask_t _unused_nodemask_arg_;
> > *
> > * Can be used to provide arguments for '%*pb[l]' when printing a nodemask.
> > */
> > -#define nodemask_pr_args(maskp) MAX_NUMNODES, (maskp)->bits
> > +#define nodemask_pr_args(maskp) MAX_NUMNODES, (maskp) ? (maskp)->bits : NULL
> >
> > /*
> > * The inline keyword gives the compiler room to decide to inline, or
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> []
> > @@ -902,6 +902,9 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
> > int cur, rbot, rtop;
> > bool first = true;
> >
> > + if (!bitmap)
> > + return buf;
>
> I believe this is not necessary as any NULL pointer argument
> passed to lib/vsprintf.c:pointer() (any %p<foo>) emits
> "[2 or 10 spaces](null)" on 32bit or 64 bit systems.
OK, I see
if (!ptr && *fmt != 'K') {
/*
* Print (null) with the same width as a pointer so it makes
* tabular output look nice.
*/
if (spec.field_width == -1)
spec.field_width = default_width;
return string(buf, end, "(null)", spec);
}
> I believe, but have not tested, that using a specific width
> as an argument to %*pb[l] will constrain the number of
> spaces before the '(null)' output in any NULL pointer use.
>
> So how about a #define like
>
> /*
> * nodemask_pr_args is only used with a "%*pb[l]" format for a nodemask.
> * A NULL nodemask uses 6 to emit "(null)" without leading spaces.
> */
> #define nodemask_pr_args(maskp) \
> (maskp) ? MAX_NUMNODES : 6, \
> (maskp) ? (maskp)->bits : NULL
Why not -1 then?
--
Michal Hocko
SUSE Labs
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