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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 419B8C43334 for ; Sat, 25 Jun 2022 09:42:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AE92B8E02A1; Sat, 25 Jun 2022 05:42:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A98F58E029A; Sat, 25 Jun 2022 05:42:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9885C8E02A1; Sat, 25 Jun 2022 05:42:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 8A1478E029A for ; Sat, 25 Jun 2022 05:42:23 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 5981C204ED for ; Sat, 25 Jun 2022 09:42:23 +0000 (UTC) X-FDA: 79616267766.01.BF17F2E Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by imf13.hostedemail.com (Postfix) with ESMTP id 1560B2001E for ; Sat, 25 Jun 2022 09:42:21 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.53]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4LVTXQ3Ym2zDsSD; Sat, 25 Jun 2022 17:41:42 +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; Sat, 25 Jun 2022 17:42:18 +0800 Subject: Re: [PATCH v2 3/9] mm/hugetlb: make pud_huge() and 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 , , Linux-MM References: <20220623235153.2623702-1-naoya.horiguchi@linux.dev> <20220623235153.2623702-4-naoya.horiguchi@linux.dev> From: Miaohe Lin Message-ID: <098b5a5c-2c05-4e22-b1ba-81f858391cd6@huawei.com> Date: Sat, 25 Jun 2022 17:42:17 +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: <20220623235153.2623702-4-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: dggems705-chm.china.huawei.com (10.3.19.182) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf13.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656150142; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0JogZYa/idAR3GJ+Fs9hV8GDCPccyUhBlAqnDqGxuAU=; b=TPjmAeGmd1lRfSt8IfhvbY9Dk672oTbHmXdqGwLcqbyvdsNwtYx2JgvUkAcEzCOoIHVD0R peS/PAcEa//svOOJM3d91ogSoLfV1iikRshXoivzfM3iSr554DwR6iiaQtO9HhxcbNCfWh Ll3PScVAVwgLVRplcOze3yZrAKhoso4= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656150142; a=rsa-sha256; cv=none; b=xJa4QHOoQPmuzhGBSdYEiud63ImOmX8lw23y9QuAdUGiQFuVPFnsJQn4g1omJKX6zv28wB MIQB4mRzGU8V8eIu9vVPbqtQdQN7VhI0+UPHvU5csmO3EIjmdlyevnqimwRektb63Twm3z 7mVW6giLr6xzZYHmdngGnscmtGR6iOI= X-Stat-Signature: 1smgw16xfzyidrnxh87gzdy5omtgkzkf X-Rspamd-Queue-Id: 1560B2001E X-Rspam-User: Authentication-Results: imf13.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf13.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspamd-Server: rspam12 X-HE-Tag: 1656150141-333665 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/6/24 7:51, 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 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 > --- > arch/x86/mm/hugetlbpage.c | 3 ++- > mm/hugetlb.c | 26 +++++++++++++++++++++++++- > 2 files changed, 27 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c > index a0d023cb4292..5fb86fb49ba8 100644 > --- a/arch/x86/mm/hugetlbpage.c > +++ b/arch/x86/mm/hugetlbpage.c > @@ -70,7 +70,8 @@ int pmd_huge(pmd_t pmd) > No strong opinion but a comment similar to pmd_huge might be better? /* * pmd_huge() returns 1 if @pmd 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; > } > #endif > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index f59f43c06601..b7ae5f73f3b2 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -6946,10 +6946,34 @@ struct page * __weak > follow_huge_pud(struct mm_struct *mm, unsigned long address, > pud_t *pud, int flags) > { > + struct page *page = NULL; > + spinlock_t *ptl; > + pte_t pte; > + > if (flags & (FOLL_GET | FOLL_PIN)) > return NULL; Should the above check be modified? It seems the below try_grab_page might not grab the page as expected (as Mike pointed out). Or the extra page refcnt is unneeded? > > - 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; > + } Again. No strong opinion but a comment similar to follow_huge_pmd might be better? /* * hwpoisoned entry is treated as no_page_table in * follow_page_mask(). */ Thanks! > + } > +out: > + spin_unlock(ptl); > + return page; > } > > struct page * __weak >