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Message-ID: <YzQHf8DOogqejrlP@strix-laptop>
Date: Wed, 28 Sep 2022 16:36:15 +0800
From: Chih-En Lin <shiyn.lin@...il.com>
To: John Hubbard <jhubbard@...dia.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Qi Zheng <zhengqi.arch@...edance.com>,
David Hildenbrand <david@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Christophe Leroy <christophe.leroy@...roup.eu>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
Iurii Zaikin <yzaikin@...gle.com>,
Vlastimil Babka <vbabka@...e.cz>,
William Kucharski <william.kucharski@...cle.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Peter Xu <peterx@...hat.com>,
Suren Baghdasaryan <surenb@...gle.com>,
Arnd Bergmann <arnd@...db.de>,
Tong Tiangen <tongtiangen@...wei.com>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Li kunyu <kunyu@...china.com>, Nadav Amit <namit@...are.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Minchan Kim <minchan@...nel.org>,
Yang Shi <shy828301@...il.com>, Song Liu <song@...nel.org>,
Miaohe Lin <linmiaohe@...wei.com>,
Thomas Gleixner <tglx@...utronix.de>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Fenghua Yu <fenghua.yu@...el.com>,
Dinglan Peng <peng301@...due.edu>,
Pedro Fonseca <pfonseca@...due.edu>,
Jim Huang <jserv@...s.ncku.edu.tw>,
Huichun Feng <foxhoundsk.tw@...il.com>
Subject: Re: [RFC PATCH v2 2/9] mm: pgtable: Add sysctl to enable COW PTE
On Tue, Sep 27, 2022 at 02:22:27PM -0700, John Hubbard wrote:
> > +extern int sysctl_cow_pte_pid;
>
> So are setting a global value, to a single pid?? Only one pid at a time
> can be set up?
>
> I think that tells you already that there is a huge API problem here.
>
> As the other thread with Nadav said, this is not a sysctl. It wants to
> be a prctl(), at least the way things look so far.
I will change it to use the prctl().
Probably it will be under PR_SET_MM or create a new option.
> > +static void set_cow_pte_task(void)
> > +{
> > + struct pid *pid;
> > + struct task_struct *task;
> > +
> > + pid = find_get_pid(sysctl_cow_pte_pid);
>
> This seems to be missing a corresponding call to put_pid().
Thanks.
> thanks,
>
> --
> John Hubbard
> NVIDIA
>
Best regards,
Chih-En Lin
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