From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8ED98C43334 for ; Tue, 5 Jul 2022 02:46:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234456AbiGECqP (ORCPT ); Mon, 4 Jul 2022 22:46:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231154AbiGECqN (ORCPT ); Mon, 4 Jul 2022 22:46:13 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1C12A1277D for ; Mon, 4 Jul 2022 19:46:12 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4LcRp22hFrzkWhL; Tue, 5 Jul 2022 10:44:10 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 5 Jul 2022 10:46:09 +0800 Subject: Re: [mm-unstable PATCH v4 3/9] mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry To: Naoya Horiguchi , CC: Andrew Morton , David Hildenbrand , Mike Kravetz , Liu Shixin , Yang Shi , Oscar Salvador , Muchun Song , Naoya Horiguchi , References: <20220704013312.2415700-1-naoya.horiguchi@linux.dev> <20220704013312.2415700-4-naoya.horiguchi@linux.dev> From: Miaohe Lin Message-ID: <83aff2eb-7190-7f5d-d81d-3eff0f56c40e@huawei.com> Date: Tue, 5 Jul 2022 10:46:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20220704013312.2415700-4-naoya.horiguchi@linux.dev> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/4 9:33, Naoya Horiguchi wrote: > From: Naoya Horiguchi > > follow_pud_mask() does not support non-present pud entry now. As long as > I tested on x86_64 server, follow_pud_mask() still simply returns > no_page_table() for non-present_pud_entry() due to pud_bad(), so no severe > user-visible effect should happen. But generally we should call > follow_huge_pud() for non-present pud entry for 1GB hugetlb page. > > Update pud_huge() and follow_huge_pud() to handle non-present pud entries. > The changes are similar to previous works for pud entries commit e66f17ff7177 > ("mm/hugetlb: take page table lock in follow_huge_pmd()") and commit > cbef8478bee5 ("mm/hugetlb: pmd_huge() returns true for non-present hugepage"). > > Signed-off-by: Naoya Horiguchi > --- > v2 -> v3: > - fixed typos in subject and description, > - added comment on pud_huge(), > - added comment about fallback for hwpoisoned entry, > - updated initial check about FOLL_{PIN,GET} flags. > --- > arch/x86/mm/hugetlbpage.c | 8 +++++++- > mm/hugetlb.c | 32 ++++++++++++++++++++++++++++++-- > 2 files changed, 37 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c > index 509408da0da1..6b3033845c6d 100644 > --- a/arch/x86/mm/hugetlbpage.c > +++ b/arch/x86/mm/hugetlbpage.c > @@ -30,9 +30,15 @@ int pmd_huge(pmd_t pmd) > (pmd_val(pmd) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT; > } > > +/* > + * pud_huge() returns 1 if @pud is hugetlb related entry, that is normal > + * hugetlb entry or non-present (migration or hwpoisoned) hugetlb entry. > + * Otherwise, returns 0. > + */ > int pud_huge(pud_t pud) > { > - return !!(pud_val(pud) & _PAGE_PSE); > + return !pud_none(pud) && > + (pud_val(pud) & (_PAGE_PRESENT|_PAGE_PSE)) != _PAGE_PRESENT; > } Question: Is aarch64 supported too? It seems aarch64 version of pud_huge matches the requirement naturally for me. Anyway, this patch looks good to me. Reviewed-by: Miaohe Lin Thanks. > > #ifdef CONFIG_HUGETLB_PAGE > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index ad621688370b..66bb39e0fce8 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6994,10 +6994,38 @@ struct page * __weak > follow_huge_pud(struct mm_struct *mm, unsigned long address, > pud_t *pud, int flags) > { > - if (flags & (FOLL_GET | FOLL_PIN)) > + struct page *page = NULL; > + spinlock_t *ptl; > + pte_t pte; > + > + if (WARN_ON_ONCE(flags & FOLL_PIN)) > return NULL; > > - return pte_page(*(pte_t *)pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT); > +retry: > + ptl = huge_pte_lock(hstate_sizelog(PUD_SHIFT), mm, (pte_t *)pud); > + if (!pud_huge(*pud)) > + goto out; > + pte = huge_ptep_get((pte_t *)pud); > + if (pte_present(pte)) { > + page = pud_page(*pud) + ((address & ~PUD_MASK) >> PAGE_SHIFT); > + if (WARN_ON_ONCE(!try_grab_page(page, flags))) { > + page = NULL; > + goto out; > + } > + } else { > + if (is_hugetlb_entry_migration(pte)) { > + spin_unlock(ptl); > + __migration_entry_wait(mm, (pte_t *)pud, ptl); > + goto retry; > + } > + /* > + * hwpoisoned entry is treated as no_page_table in > + * follow_page_mask(). > + */ > + } > +out: > + spin_unlock(ptl); > + return page; > } > > struct page * __weak >