linux-kernel - Re: [PATCH 06/11] mm: page_vma_mapped_walk(): crossing page table boundary

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Message-ID: <20210611112335.37sno6wwbsef6zen@box.shutemov.name>
Date:   Fri, 11 Jun 2021 14:23:35 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>,
        Wang Yugui <wangyugui@...-tech.com>,
        Matthew Wilcox <willy@...radead.org>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>, Zi Yan <ziy@...dia.com>,
        Peter Xu <peterx@...hat.com>, Will Deacon <will@...nel.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/11] mm: page_vma_mapped_walk(): crossing page table
 boundary

On Thu, Jun 10, 2021 at 04:02:47PM -0700, Hugh Dickins wrote:
> On Thu, 10 Jun 2021, Kirill A. Shutemov wrote:
> > On Wed, Jun 09, 2021 at 11:44:10PM -0700, Hugh Dickins wrote:
> > > page_vma_mapped_walk() cleanup: adjust the test for crossing page table
> > > boundary - I believe pvmw->address is always page-aligned, but nothing
> > > else here assumed that;
> > 
> > Maybe we should just get it aligned instead? (PMD_SIZE - PAGE_SIZE) is not
> > most obvious mask calculation.
> 
> Would you prefer it with another line of comment after the
> /* Did we cross page table boundary? */
> 
> Maybe,
> /* Is address always page-aligned? No need to assume that. */
> 
> I just don't see the point in forcing alignment when the test is good
> (and don't know for sure whether address is always aligned there or not).
> 
> I prefer to leave it as is, just letting the commit message document it.

Okay.

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov