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 14269C433F5 for ; Tue, 8 Mar 2022 00:50:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1C9818D0002; Mon, 7 Mar 2022 19:50:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 179F98D0001; Mon, 7 Mar 2022 19:50:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 068D98D0002; Mon, 7 Mar 2022 19:50:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0129.hostedemail.com [216.40.44.129]) by kanga.kvack.org (Postfix) with ESMTP id EB3FC8D0001 for ; Mon, 7 Mar 2022 19:50:19 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A8818824C420 for ; Tue, 8 Mar 2022 00:50:19 +0000 (UTC) X-FDA: 79219387758.24.33E3E86 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf19.hostedemail.com (Postfix) with ESMTP id C8FF31A000B for ; Tue, 8 Mar 2022 00:50:18 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5B6FEB81752; Tue, 8 Mar 2022 00:50:17 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD099C340EF; Tue, 8 Mar 2022 00:50:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646700616; bh=Kv+yY9E+DYOUfGXI4e3etZBeNRkR4t4l0wyhFQINGm4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=icoTRQd5NmdJTiFKjqLxohZMoKg1VLUj244SwSAg3OjjkIg4C0hSdDvv8VB73qd5h tKSNRNKZhlTu24R5AuQLD5Oz4CiNZ4o0SBneRR5sUTHkD7XnaQlvTR+W/ocnxGJL83 p5kij24S6LMz1dJ82NPR3HZmFIae5LFUOtmHU5Ys= Date: Mon, 7 Mar 2022 16:50:15 -0800 From: Andrew Morton To: Yang Shi Cc: David Hildenbrand , Andrea Arcangeli , Hugh Dickins , "Kirill A. Shutemov" , Linux Kernel Mailing List , Linux MM , Matthew Wilcox Subject: Re: [PATCH] mm: thp: don't have to lock page anymore when splitting PMD Message-Id: <20220307165015.77fbcbe9e1fa2fe15f3eb239@linux-foundation.org> In-Reply-To: References: <20220303222014.517033-1-shy828301@gmail.com> <13ad4ba1-2a88-9459-3995-70af36aba33e@redhat.com> <20220306180718.6d4e6233130b94fdad98df88@linux-foundation.org> <84a6c9c1-d18f-6955-2666-0a2d7bce6094@redhat.com> <20220307154326.6494f7fca7def491a23e5df1@linux-foundation.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C8FF31A000B X-Stat-Signature: tanj5f6ykr9wr4mktk54k6aoee3ukhkw Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=icoTRQd5; spf=pass (imf19.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-HE-Tag: 1646700618-250184 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 Mon, 7 Mar 2022 16:03:12 -0800 Yang Shi wrote: > On Mon, Mar 7, 2022 at 3:43 PM Andrew Morton wrote: > > @@ -2133,8 +2133,6 @@ void __split_huge_pmd(struct vm_area_str > > { > > spinlock_t *ptl; > > struct mmu_notifier_range range; > > - bool do_unlock_folio = false; > > - pmd_t _pmd; > > > > mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, > > address & HPAGE_PMD_MASK, > > @@ -2153,42 +2151,14 @@ void __split_huge_pmd(struct vm_area_str > > goto out; > > } > > > > -repeat: > > if (pmd_trans_huge(*pmd)) { > > - if (!folio) { > > + if (!folio) > > folio = page_folio(pmd_page(*pmd)); > > We could remove the "if (pmd_trans_huge(*pmd))" section since folio is > actually not used afterward at all. > > ... > > > With the above if removed, this could be changed to: > > if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || > is_pmd_migration_entry(*pmd)) > __split_huge_pmd_locked(vma, pmd, range.start, freeze); > OK, looks sane. Can someone please test all this? --- a/mm/huge_memory.c~mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd-fix +++ a/mm/huge_memory.c @@ -2151,12 +2151,10 @@ void __split_huge_pmd(struct vm_area_str goto out; } - if (pmd_trans_huge(*pmd)) { - if (!folio) - folio = page_folio(pmd_page(*pmd)); - } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) - goto out; - __split_huge_pmd_locked(vma, pmd, range.start, freeze); + if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) || + is_pmd_migration_entry(*pmd))) + __split_huge_pmd_locked(vma, pmd, range.start, freeze); + out: spin_unlock(ptl); /* _