From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 377646B025F for ; Fri, 18 Aug 2017 09:49:46 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id r133so170329773pgr.6 for ; Fri, 18 Aug 2017 06:49:46 -0700 (PDT) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id g3si4020131plk.281.2017.08.18.06.49.44 for ; Fri, 18 Aug 2017 06:49:45 -0700 (PDT) From: Punit Agrawal Subject: Re: [PATCH v6 5/9] arm64: hugetlb: Handle swap entries in huge_pte_offset() for contiguous hugepages References: <20170810170906.30772-1-punit.agrawal@arm.com> <20170810170906.30772-6-punit.agrawal@arm.com> <20170818112015.2cvkb7y3gkozz5ip@armageddon.cambridge.arm.com> Date: Fri, 18 Aug 2017 14:49:41 +0100 In-Reply-To: <20170818112015.2cvkb7y3gkozz5ip@armageddon.cambridge.arm.com> (Catalin Marinas's message of "Fri, 18 Aug 2017 12:20:16 +0100") Message-ID: <87inhlnfyi.fsf@e105922-lin.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Catalin Marinas Cc: will.deacon@arm.com, mark.rutland@arm.com, David Woods , steve.capper@arm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org Catalin Marinas writes: > On Thu, Aug 10, 2017 at 06:09:02PM +0100, Punit Agrawal wrote: >> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c >> index d3a6713048a2..09e79785c019 100644 >> --- a/arch/arm64/mm/hugetlbpage.c >> +++ b/arch/arm64/mm/hugetlbpage.c >> @@ -210,6 +210,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, >> pgd_t *pgd; >> pud_t *pud; >> pmd_t *pmd; >> + pte_t *pte; >> >> pgd = pgd_offset(mm, addr); >> pr_debug("%s: addr:0x%lx pgd:%p\n", __func__, addr, pgd); >> @@ -217,19 +218,29 @@ pte_t *huge_pte_offset(struct mm_struct *mm, >> return NULL; >> >> pud = pud_offset(pgd, addr); >> - if (pud_none(*pud)) >> + if (pud_none(*pud) && sz != PUD_SIZE) >> return NULL; >> /* swap or huge page */ >> if (!pud_present(*pud) || pud_huge(*pud)) >> return (pte_t *)pud; >> /* table; check the next level */ > > So if sz == PUD_SIZE and we have pud_none(*pud) == true, it returns the > pud. Isn't this different from what you proposed for the generic > huge_pte_offset()? [1] I think I missed this case in the generic version. As hugetlb_fault() deals with p*d_none() entries by calling hugetlb_no_page(), the thinking was that returning the p*d saves us an extra round trip by avoiding the call to huge_pte_alloc(). > >> >> + if (sz == CONT_PMD_SIZE) >> + addr &= CONT_PMD_MASK; >> + >> pmd = pmd_offset(pud, addr); >> - if (pmd_none(*pmd)) >> + if (pmd_none(*pmd) && >> + !(sz == PMD_SIZE || sz == CONT_PMD_SIZE)) >> return NULL; > > Again, if sz == PMD_SIZE, you no longer return NULL. The generic > proposal in [1] looks like: > > if (pmd_none(*pmd)) > return NULL; > > and that's even when sz == PMD_SIZE. > > Anyway, I think we need to push for [1] again to be accepted before we > go ahead with these changes. [1] is already queued in Andrew's tree. I'll send an update - hopefully it can be picked up for the next merge. > > [1] http://lkml.kernel.org/r/20170725154114.24131-2-punit.agrawal@arm.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org