Re: [PATCH v2] mm: add account_locked_vm utility function

From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Ira Weiny <ira.weiny@intel.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>,
	akpm@linux-foundation.org, Alexey Kardashevskiy <aik@ozlabs.ru>,
	Alan Tull <atull@kernel.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Christoph Lameter <cl@linux.com>,
	Christophe Leroy <christophe.leroy@c-s.fr>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Jason Gunthorpe <jgg@mellanox.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Moritz Fischer <mdf@kernel.org>,
	Paul Mackerras <paulus@ozlabs.org>,
	Steve Sistare <steven.sistare@oracle.com>,
	Wu Hao <hao.wu@intel.com>,
	linux-mm@kvack.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org,
	linuxppc-dev@lists.ozlabs.org, linux-fpga@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] mm: add account_locked_vm utility function
Date: Wed, 29 May 2019 14:35:59 -0400	[thread overview]
Message-ID: <20190529183559.jzkpvbdiimnp3n2m@ca-dmjordan1.us.oracle.com> (raw)
In-Reply-To: <20190529180547.GA16182@iweiny-DESK2.sc.intel.com>

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.