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 8299CC433F5 for ; Mon, 7 Mar 2022 23:43:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343952AbiCGXo3 (ORCPT ); Mon, 7 Mar 2022 18:44:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243825AbiCGXoY (ORCPT ); Mon, 7 Mar 2022 18:44:24 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E156ADE93 for ; Mon, 7 Mar 2022 15:43:28 -0800 (PST) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 451A8611BD for ; Mon, 7 Mar 2022 23:43:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 62D90C340E9; Mon, 7 Mar 2022 23:43:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1646696607; bh=K+xM2GYxG+Lby5uXP6tawrxb1rgWkjnt9Wizwmuhnv0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nD0MAVoJBfgAsY2ADPp/+vQL+L/fwENBHD3KiA5kTcTB8Txh9Ff6CJ7CVy8HGM04O 2aeTOjSgrkwybDFVMmXX+WTp1pv83XQfbwNDLeTOARSHgexEqSqCz7u/ro92chBKWh 4Svlb+OkVq8Dlfs29jPS3fj1L7jpqmeS+dQKKJ84= Date: Mon, 7 Mar 2022 15:43:26 -0800 From: Andrew Morton To: David Hildenbrand Cc: Yang Shi , 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: <20220307154326.6494f7fca7def491a23e5df1@linux-foundation.org> In-Reply-To: <84a6c9c1-d18f-6955-2666-0a2d7bce6094@redhat.com> 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> 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 7 Mar 2022 09:24:58 +0100 David Hildenbrand wrote: > On 07.03.22 03:07, Andrew Morton wrote: > > On Fri, 4 Mar 2022 19:50:08 +0100 David Hildenbrand wrote: > > > >> @Andrew, the last mail I received was > >> > >> + mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd.patch > >> added to -mm tree > >> > >> The patch shows up in mmotm as > >> > >> #[merged]mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd.patch > >> > >> ... which shouldn't be true. > > > > I guess I mislabelled the reason for dropping it. Should have been to-be-updated, > > due to https://lkml.kernel.org/r/CAHbLzkpbnQyHRckoRtbZoaLvANu92MY4kEsbKudaQ8MDUA3nVg@mail.gmail.com > > > > Let me clarify. > > 1. I sent [1] (9 patches) > > 2. You queued the 9 patches > > E.g., in "mmotm 2022-02-15-20-22 uploaded" > > * mm-optimize-do_wp_page-for-exclusive-pages-in-the-swapcache.patch > * mm-optimize-do_wp_page-for-fresh-pages-in-local-lru-pagevecs.patch > * mm-slightly-clarify-ksm-logic-in-do_swap_page.patch > * mm-streamline-cow-logic-in-do_swap_page.patch > * mm-huge_memory-streamline-cow-logic-in-do_huge_pmd_wp_page.patch > * mm-khugepaged-remove-reuse_swap_page-usage.patch > * mm-swapfile-remove-stale-reuse_swap_page.patch > * mm-huge_memory-remove-stale-page_trans_huge_mapcount.patch > * mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd.patch > > 3. The last patch in the series was dropped. What remains are 8 patches. > > E.g., in "mmotm 2022-02-24-22-38 uploaded" > > * mm-optimize-do_wp_page-for-exclusive-pages-in-the-swapcache.patch > * mm-optimize-do_wp_page-for-fresh-pages-in-local-lru-pagevecs.patch > * mm-slightly-clarify-ksm-logic-in-do_swap_page.patch > * mm-streamline-cow-logic-in-do_swap_page.patch > * mm-huge_memory-streamline-cow-logic-in-do_huge_pmd_wp_page.patch > * mm-khugepaged-remove-reuse_swap_page-usage.patch > * mm-swapfile-remove-stale-reuse_swap_page.patch > * mm-huge_memory-remove-stale-page_trans_huge_mapcount.patch > > 4. Yang Shi sent his patch (the one we're replying to) > > 5. You picked his patch and dropped it again due to [2] > > > I'm wondering why 3 happened and why > https://www.ozlabs.org/~akpm/mmotm/series contains: > > > mm-optimize-do_wp_page-for-exclusive-pages-in-the-swapcache.patch > mm-optimize-do_wp_page-for-fresh-pages-in-local-lru-pagevecs.patch > mm-slightly-clarify-ksm-logic-in-do_swap_page.patch > mm-streamline-cow-logic-in-do_swap_page.patch > mm-huge_memory-streamline-cow-logic-in-do_huge_pmd_wp_page.patch > mm-khugepaged-remove-reuse_swap_page-usage.patch > mm-swapfile-remove-stale-reuse_swap_page.patch > mm-huge_memory-remove-stale-page_trans_huge_mapcount.patch > ... > #[merged]mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd.patch OK, thanks. I guess it was me seeing 100% rejects when merging onto the folio changes then incorrectly deciding the patch was now in linux-next via some other tree. I restored it and fixed things up. Please check. --- a/mm/huge_memory.c~mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd +++ a/mm/huge_memory.c @@ -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)); - /* - * An anonymous page must be locked, to ensure that a - * concurrent reuse_swap_page() sees stable mapcount; - * but reuse_swap_page() is not used on shmem or file, - * and page lock must not be taken when zap_pmd_range() - * calls __split_huge_pmd() while i_mmap_lock is held. - */ - if (folio_test_anon(folio)) { - if (unlikely(!folio_trylock(folio))) { - folio_get(folio); - _pmd = *pmd; - spin_unlock(ptl); - folio_lock(folio); - spin_lock(ptl); - if (unlikely(!pmd_same(*pmd, _pmd))) { - folio_unlock(folio); - folio_put(folio); - folio = NULL; - goto repeat; - } - folio_put(folio); - } - do_unlock_folio = true; - } - } } else if (!(pmd_devmap(*pmd) || is_pmd_migration_entry(*pmd))) goto out; __split_huge_pmd_locked(vma, pmd, range.start, freeze); out: spin_unlock(ptl); - if (do_unlock_folio) - folio_unlock(folio); /* * No need to double call mmu_notifier->invalidate_range() callback. * They are 3 cases to consider inside __split_huge_pmd_locked(): _