linux-kernel - Re: [PATCH v2] mm: add account_locked

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Message-ID: <20190529183559.jzkpvbdiimnp3n2m@ca-dmjordan1.us.oracle.com>
Date:   Wed, 29 May 2019 14:35:59 -0400
From:   Daniel Jordan <daniel.m.jordan@...cle.com>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Daniel Jordan <daniel.m.jordan@...cle.com>,
        akpm@...ux-foundation.org, 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>,
        Christophe Leroy <christophe.leroy@....fr>,
        Davidlohr Bueso <dave@...olabs.net>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Mark Rutland <mark.rutland@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Moritz Fischer <mdf@...nel.org>,
        Paul Mackerras <paulus@...abs.org>,
        Steve Sistare <steven.sistare@...cle.com>,
        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 v2] mm: add account_locked_vm utility function

On Wed, May 29, 2019 at 11:05:48AM -0700, Ira Weiny wrote:
> On Fri, May 24, 2019 at 01:50:45PM -0400, Daniel Jordan wrote:
> > +static inline int account_locked_vm(struct mm_struct *mm, unsigned long pages,
> > +				    bool inc)
> > +{
> > +	int ret;
> > +
> > +	if (pages == 0 || !mm)
> > +		return 0;
> > +
> > +	down_write(&mm->mmap_sem);
> > +	ret = __account_locked_vm(mm, pages, inc, current,
> > +				  capable(CAP_IPC_LOCK));
> > +	up_write(&mm->mmap_sem);
> > +
> > +	return ret;
> > +}
> > +
...snip...
> > +/**
> > + * __account_locked_vm - account locked pages to an mm's locked_vm
> > + * @mm:          mm to account against, may be NULL
> 
> This kernel doc is wrong.  You dereference mm straight away...
...snip...
> > +
> > +	locked_vm = mm->locked_vm;
> 
> here...
> 
> Perhaps the comment was meant to document account_locked_vm()?

Yes, the comment got out of sync when I moved the !mm check outside
__account_locked_vm.  Thanks for catching, will fix.