From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f72.google.com (mail-lf0-f72.google.com [209.85.215.72]) by kanga.kvack.org (Postfix) with ESMTP id A2B996B0069 for ; Mon, 22 Aug 2016 08:09:40 -0400 (EDT) Received: by mail-lf0-f72.google.com with SMTP id p85so73077191lfg.3 for ; Mon, 22 Aug 2016 05:09:40 -0700 (PDT) Received: from mail-wm0-f68.google.com (mail-wm0-f68.google.com. [74.125.82.68]) by mx.google.com with ESMTPS id w192si15937886wmd.82.2016.08.22.05.09.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Aug 2016 05:09:39 -0700 (PDT) Received: by mail-wm0-f68.google.com with SMTP id i138so13131902wmf.3 for ; Mon, 22 Aug 2016 05:09:38 -0700 (PDT) Date: Mon, 22 Aug 2016 14:09:37 +0200 From: Michal Hocko Subject: Re: [PATCH 2/2] proc: task_mmu: Reduce output processing cpu time Message-ID: <20160822120937.GK13596@dhcp22.suse.cz> References: <2c1ea0d8f35fa5ddea477369b273d6d91c5bf2e2.1471679737.git.joe@perches.com> <20160822072414.GB13596@dhcp22.suse.cz> <1471852859.3746.42.camel@perches.com> <1471854614.3746.46.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1471854614.3746.46.camel@perches.com> Sender: owner-linux-mm@kvack.org List-ID: To: Joe Perches Cc: linux-kernel@vger.kernel.org, Andrew Morton , Jann Horn , linux-mm@kvack.org On Mon 22-08-16 01:30:14, Joe Perches wrote: > On Mon, 2016-08-22 at 01:00 -0700, Joe Perches wrote: > > On Mon, 2016-08-22 at 09:24 +0200, Michal Hocko wrote: > > > On Sat 20-08-16 01:00:17, Joe Perches wrote: > [] > > > > static int proc_maps_open(struct inode *inode, struct file *file, > > > > const struct seq_operations *ops, int psize) > > > > { > > > > - struct proc_maps_private *priv = __seq_open_private(file, ops, psize); > > > > + struct proc_maps_private *priv; > > > > + struct mm_struct *mm; > > > > + > > > > + mm = proc_mem_open(inode, PTRACE_MODE_READ); > > > > + if (IS_ERR(mm)) > > > > + return PTR_ERR(mm); > > > > > > > > + priv = __seq_open_private_bufsize(file, ops, psize, > > > > + mm && mm->map_count ? > > > > + mm->map_count * 0x300 : PAGE_SIZE); > > > NAK to this! > > > > > > Seriously, this just gives any random user access to user > > > defined amount of memory which not accounted, not reclaimable and a > > > potential consumer of any higher order blocks. > > I completely disagree here with your rationale here. > > And with further review and your comment above, I withdraw this patch. So you've made me look into that code. I can imagine how it is easy to to get confused here. The important part is that m->count is reset after each ->show(). So traverse() same as seq_read only grows the buffer if a single show doesn't fit in. That being said, should I repost my rebased patches or do you plan to repost your patch? I do not want spam people with another version if you do not like it. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org