linux-kernel - Re: [RFC PATCH v2 1/5] mm: make HPAGE_PxD

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Message-ID: <20200710170853.GB11749@redhat.com>
Date:   Fri, 10 Jul 2020 13:08:53 -0400
From:   Andrea Arcangeli <aarcange@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Hugh Dickins <hughd@...gle.com>, Mike Rapoport <rppt@...nel.org>,
        linux-kernel@...r.kernel.org, Alan Cox <alan@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Christopher Lameter <cl@...ux.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Idan Yaniv <idan.yaniv@....com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Peter Zijlstra <peterz@...radead.org>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, linux-api@...r.kernel.org,
        linux-mm@...ck.org, Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [RFC PATCH v2 1/5] mm: make HPAGE_PxD_{SHIFT,MASK,SIZE} always
 available

On Fri, Jul 10, 2020 at 05:57:46PM +0100, Matthew Wilcox wrote:
> btw, using the hpage_ prefix already caused one problem in the hugetlb
> code:
> 
> https://lore.kernel.org/linux-mm/20200629185003.97202-1-mike.kravetz@oracle.com/
> 
> I'd suggest we rename these to THP_PMD_* and THP_PUD_* to make it clear
> they're only for the THP case.

The confusion seem to have happened only about hpage_nr_pages not
about HPAGE_PMD_*. It's just the hpage_ prefix alone that is commonly
used by hugetlbfs only and so it's not surprising it caused confusion.

So I certainly agree hpage_nr_pages would better be renamed to
something more THP specific (either hpage_pmd_nr_pages or
trans_huge_nr_pages or as you wish), but HPAGE_PMD_ don't look too
confusing about the fact it's only for the THP case since the non-THP
case won't necessarily care about PMDs.

Thanks,
Andrea