linux-kernel - Re: [PATCH v4 3/3] vsprintf: dump full information of page flags in pGp

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Message-ID: <5e1e5415dc1bcda37df3ce07a18827172c2a5b7f.camel@perches.com>
Date:   Wed, 10 Feb 2021 05:04:07 -0800
From:   Joe Perches <joe@...ches.com>
To:     Petr Mladek <pmladek@...e.com>, Yafang Shao <laoar.shao@...il.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Christoph Lameter <cl@...ux.com>, penberg@...nel.org,
        David Rientjes <rientjes@...gle.com>, iamjoonsoo.kim@....com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] vsprintf: dump full information of page flags in
 pGp

On Wed, 2021-02-10 at 13:51 +0100, Petr Mladek wrote:
> On Wed 2021-02-10 00:21:37, Yafang Shao wrote:
> > On Tue, Feb 9, 2021 at 9:53 PM Petr Mladek <pmladek@...e.com> wrote:
[]
> >  for (p = pff; p < pff + ARRAY_SIZE(pff); p++) {
> 
> This looks a bit non-standard. IMHO, Joe was not against using index.
> He proposed:
> 
> 	for (i = 0; i < ARRAY_SIZE(pfl) && buf < end; i++) {
> 
> , see
> https://lore.kernel.org/lkml/e5ea9e8b1190c2a397a1b84dd55bb9c706dc7058.camel@perches.com/
> 
> I am not sure about the (buf < end) check. It might be some
> optimization or it did fit the the old code.

I believe the buf < end bit was broken anyway.

I believe vsprintf is supposed to return the maximum possible length
of the output and the function should not restrict that.  The
function should not write beyond the specified end.
 
> Anyway, I like the currently used:
> 
> 	for (i = 0; i < ARRAY_SIZE(pff); i++) {
> 
> It is standard, easy to understand, and thus more safe. I am sure that
> compiler will optimize it very well.

true.