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 E1776C77B75 for ; Mon, 22 May 2023 11:17:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 77575900004; Mon, 22 May 2023 07:17:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7263B900002; Mon, 22 May 2023 07:17:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5ED40900004; Mon, 22 May 2023 07:17:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 4C50E900002 for ; Mon, 22 May 2023 07:17:29 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id E920780D76 for ; Mon, 22 May 2023 11:17:28 +0000 (UTC) X-FDA: 80817640176.20.F6913BE Received: from out-37.mta1.migadu.com (out-37.mta1.migadu.com [95.215.58.37]) by imf12.hostedemail.com (Postfix) with ESMTP id DAA6640015 for ; Mon, 22 May 2023 11:17:26 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=dkzcgRbs; spf=pass (imf12.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.37 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1684754247; 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:dkim-signature; bh=3BNPsU4rNUqUjN43wlS41FKIQSqyrj6MltULGYMl8TA=; b=NGwyleyj3x8FBRI5Da2XoZPJC02jT8goSM6TGN4EoAMiJuRTBJgkjWzZsuvHhxSRV4itle EfJAb0Vx0FQVz38Al1w9a9/FPNtwPR8Zsz0R6yjEPnaaD9Qo4Aa/Y0hrHoaWfFLmMH+9po 2HLMZ0i5KW9VxjfvzgtMNZyRV8Vexlk= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=dkzcgRbs; spf=pass (imf12.hostedemail.com: domain of qi.zheng@linux.dev designates 95.215.58.37 as permitted sender) smtp.mailfrom=qi.zheng@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1684754247; a=rsa-sha256; cv=none; b=K6hCvJnFOAkKWKuYEz1cpUEpGd7NwmyPb9iexL6vptgbQCzayJ4GvrAhVqF7AzdktQBP/1 +SE7jh8Udl2CR3sUkX+apsEFvY4cPCUorvUqNFj1l3n3WaJBANN8eWke8EDf+55gE5Pwcj +F3G1J5pv7dD03Q5nboyg4YZzidACsg= Message-ID: <9dc72654-79db-e988-54a8-488550d235ac@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1684754244; h=from:from: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=3BNPsU4rNUqUjN43wlS41FKIQSqyrj6MltULGYMl8TA=; b=dkzcgRbsbeMyA8WuRNLFxGPf+kefcNrXeWfOoPgOxGVvRYK/kTHZvSS2JE+w2quBdOzMr0 e5sSlGZgGRFN8iE5U3L7qkVTBaJFJnFZf+soYncMIncoNch7colJt7oyjKHuFT/KmYxDNW VN5qJGHn6LMvUSikM0IlvbDC1uY4BN0= Date: Mon, 22 May 2023 19:17:11 +0800 MIME-Version: 1.0 Subject: Re: [PATCH 04/31] mm/pgtable: allow pte_offset_map[_lock]() to fail Content-Language: en-US To: Hugh Dickins , Andrew Morton Cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <68a97fbe-5c1e-7ac6-72c-7b9c6290b370@google.com> <8218ffdc-8be-54e5-0a8-83f5542af283@google.com> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Qi Zheng In-Reply-To: <8218ffdc-8be-54e5-0a8-83f5542af283@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: DAA6640015 X-Rspam-User: X-Stat-Signature: f9kksn6a839qr3jemera9e9fxcguwh1d X-Rspamd-Server: rspam01 X-HE-Tag: 1684754246-819312 X-HE-Meta: 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 Z3iH/fx3 EzvjeqzJPL3UqM2qzGV7PhhoEJ+2C1tmzhQdkgvwOfgI/RgHz3A4w1lv1BrNWkgHJWH1DJjxIIrJsaaeOHtH8qcBAv7e9kRzXQ49+yoiFjfJhtk5M9W73D7JVho/N5wV98+sKwyrguF5RGLQ= 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: Hi Hugh, On 2023/5/22 12:53, Hugh Dickins wrote: [...] > > @@ -229,3 +231,57 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, > } > #endif > #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > + > +pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) > +{ > + pmd_t pmdval; > + > + /* rcu_read_lock() to be added later */ > + pmdval = pmdp_get_lockless(pmd); > + if (pmdvalp) > + *pmdvalp = pmdval; > + if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) > + goto nomap; > + if (unlikely(pmd_trans_huge(pmdval) || pmd_devmap(pmdval))) > + goto nomap; Will the follow-up patch deal with the above situation specially? Otherwise, maybe it can be changed to the following check method? if (unlikely(pmd_none(pmdval) || pmd_leaf(pmdval))) goto nomap; > + if (unlikely(pmd_bad(pmdval))) { > + pmd_clear_bad(pmd); > + goto nomap; > + } > + return __pte_map(&pmdval, addr); > +nomap: > + /* rcu_read_unlock() to be added later */ > + return NULL; > +} > + > +pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, > + unsigned long addr, spinlock_t **ptlp) > +{ > + pmd_t pmdval; > + pte_t *pte; > + > + pte = __pte_offset_map(pmd, addr, &pmdval); > + if (likely(pte)) > + *ptlp = pte_lockptr(mm, &pmdval); > + return pte; > +} > + > +pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd, > + unsigned long addr, spinlock_t **ptlp) > +{ > + spinlock_t *ptl; > + pmd_t pmdval; > + pte_t *pte; > +again: > + pte = __pte_offset_map(pmd, addr, &pmdval); > + if (unlikely(!pte)) > + return pte; > + ptl = pte_lockptr(mm, &pmdval); > + spin_lock(ptl); > + if (likely(pmd_same(pmdval, pmdp_get_lockless(pmd)))) { > + *ptlp = ptl; > + return pte; > + } > + pte_unmap_unlock(pte, ptl); > + goto again; > +} -- Thanks, Qi