linux-kernel - Re: [PATCH 1/6] mm: change locked_vm's type from unsigned long to atomic64

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Date:   Tue, 16 Apr 2019 16:33:51 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Daniel Jordan <daniel.m.jordan@...cle.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Alan Tull <atull@...nel.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Lameter <cl@...ux.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        Moritz Fischer <mdf@...nel.org>,
        Paul Mackerras <paulus@...abs.org>, Wu Hao <hao.wu@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] mm: change locked_vm's type from unsigned long to
 atomic64_t

On Thu, 11 Apr 2019 16:28:07 -0400 Daniel Jordan <daniel.m.jordan@...cle.com> wrote:

> On Thu, Apr 11, 2019 at 10:55:43AM +0100, Mark Rutland wrote:
> > On Thu, Apr 11, 2019 at 02:22:23PM +1000, Alexey Kardashevskiy wrote:
> > > On 03/04/2019 07:41, Daniel Jordan wrote:
> > 
> > > > -	dev_dbg(dev, "[%d] RLIMIT_MEMLOCK %c%ld %ld/%ld%s\n", current->pid,
> > > > +	dev_dbg(dev, "[%d] RLIMIT_MEMLOCK %c%ld %lld/%lu%s\n", current->pid,
> > > >  		incr ? '+' : '-', npages << PAGE_SHIFT,
> > > > -		current->mm->locked_vm << PAGE_SHIFT, rlimit(RLIMIT_MEMLOCK),
> > > > -		ret ? "- exceeded" : "");
> > > > +		(s64)atomic64_read(&current->mm->locked_vm) << PAGE_SHIFT,
> > > > +		rlimit(RLIMIT_MEMLOCK), ret ? "- exceeded" : "");
> > > 
> > > 
> > > 
> > > atomic64_read() returns "long" which matches "%ld", why this change (and
> > > similar below)? You did not do this in the two pr_debug()s above anyway.
> > 
> > Unfortunately, architectures return inconsistent types for atomic64 ops.
> > 
> > Some return long (e..g. powerpc), some return long long (e.g. arc), and
> > some return s64 (e.g. x86).
> 
> Yes, Mark said it all, I'm just chiming in to confirm that's why I added the
> cast.
> 
> Btw, thanks for doing this, Mark.

What's the status of this patchset, btw?

I have a note here that
powerpc-mmu-drop-mmap_sem-now-that-locked_vm-is-atomic.patch is to be
updated.