Received-SPF: pass (google.com: domain of linux-kernel+bounces-119857-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Precedence: bulk
MIME-Version: 1.0
References: <20240325223339.169350-1-vishal.moola@gmail.com>
 <20240325223339.169350-5-vishal.moola@gmail.com> <ZgI1CF2dw-mauoIZ@casper.infradead.org>
In-Reply-To: <ZgI1CF2dw-mauoIZ@casper.infradead.org>
From: Vishal Moola <vishal.moola@gmail.com>
Date: Tue, 26 Mar 2024 13:06:19 -0700
Message-ID: <CAOzc2pyj54X7QpzMXcRBtoG650k3C3G+SYrsOGKDWjHXQ1yvrQ@mail.gmail.com>
Subject: Re: [PATCH 4/5] mm: Make pgoff non-const in struct vm_fault
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, 
	akpm@linux-foundation.org, muchun.song@linux.dev
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Mon, Mar 25, 2024 at 7:38=E2=80=AFPM Matthew Wilcox <willy@infradead.org=
> wrote:
>
> On Mon, Mar 25, 2024 at 03:33:38PM -0700, Vishal Moola (Oracle) wrote:
> > Hugetlb calculates addresses and page offsets differently from the rest=
 of
> > mm. In order to pass struct vm_fault through the fault pathway we will =
let
> > hugetlb_fault() and __handle_mm_fault() set those variables themselves
> > instead.
>
> I don't think this is a great idea.  I'd rather not do patch 5 than do
> patch 4+5.  If you look at the history, commits 742d33729a0df11 and
> 5857c9209ce58f show that drivers got into the bad habit of changing
> address & pgoff, so they got made const to prevent that.
>
> So can we make hugetlbfs OK with using addresses & pgoffsets that aren't
> aligned to HPAGE boundaries?  Worth playing with for a bit to see how
> deep that assumption runs.

Hmmm, I'll take a look. I don't think there should be too many issues
with that.