linux-kernel - Re: [RFC v2 3/3] mm, printk: introduce new format %pGt for page

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Message-ID: <Y2tFLQ/w9siSwy+M@hyeyoo>
Date:   Wed, 9 Nov 2022 15:14:05 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Matthew Wilcox <willy@...radead.org>,
        Minchan Kim <minchan@...nel.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Hugh Dickins <hughd@...gle.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Hildenbrand <david@...hat.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 3/3] mm, printk: introduce new format %pGt for page_type

On Sun, Nov 06, 2022 at 10:04:25AM -0800, Joe Perches wrote:
> On Sun, 2022-11-06 at 23:03 +0900, Hyeonggon Yoo wrote:
> > dump_page() uses %pGp format to print 'flags' field of struct page.
> > As some page flags (e.g. PG_buddy, see page-flags.h for more details)
> > are set in page_type field, introduce %pGt format which provides
> > human readable output of page_type. And use it in dump_page().
> []
> > diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> []
> > @@ -2056,6 +2056,28 @@ char *format_page_flags(char *buf, char *end, unsigned long flags)
> >  	return buf;
> >  }
> >  
> > +static

Thanks for looking at this.

> 
> noinline_for_stack ?

May I ask why,
Does it have issues related to stack consumption?
To Be Honest I'm a bit unsure what is purpose of this attribute.

> > +char *format_page_type(char *buf, char *end, unsigned int page_type)
> > +{
> > +	if (!(page_type & PAGE_TYPE_BASE))
> > +		return string(buf, end, "no type for user-mapped page", default_str_spec);
> 
> Might be better with something like '%pGt: no type..."

Will try something like "0x32()" when it has no type because it is
mapped to userspace.

-- 
Thanks,
Hyeonggon