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.
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
--
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