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 0FF59EB64DD for ; Thu, 27 Jul 2023 19:55:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231881AbjG0TzA (ORCPT ); Thu, 27 Jul 2023 15:55:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34698 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229995AbjG0Ty6 (ORCPT ); Thu, 27 Jul 2023 15:54:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CD6E2D73 for ; Thu, 27 Jul 2023 12:54:57 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 8D77461F28 for ; Thu, 27 Jul 2023 19:54:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DD92C433C8; Thu, 27 Jul 2023 19:54:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690487695; bh=/jP1tCMthxFNPSaqOUszBlNwQ94CB6jBYZ00mppC3O0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qfyH29vTZiN6nYEmK0Ow4XeWsSUlDWlyD0eAMjr1NYeIMgM6CuIBywSrfyCeFUdPw kG1lwWJPAVfSf0Kbq4YNX4Ogu544UZ9RagOE3raqEZsra27siYVtDkClAc5ggUK0yk i7o0MObK2/D0G7/sgcPOHohO0dYgcHc2Lz6e0L8AAoekqKp8cMNtYZtmM9aL6L9shD TbEsS9wgDCtNXk3WNhoPrVLqDQrKn802+VcYowGlZfxbSpGF0Yly/5Ta+ItjPXs1lC kkFmtwzPRzFeOaOUGrE8IJGyRIEGOQtrjIehusVrE3x7TRrngiZg6Lm8utpg47i2gM GsCGk8gsV2rJQ== From: SeongJae Park To: Levi Yun Cc: sj@kernel.org, akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] damon: Use pmdp_get instead of drect dereferencing pmd. Date: Thu, 27 Jul 2023 19:54:53 +0000 Message-Id: <20230727195453.67611-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230727183745.682880-1-ppbuk5246@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Levi, Thank you for this patch. Nit for the subject, what about s/drect/directly/? Also, let's remove the period at the end. On Fri, 28 Jul 2023 03:37:45 +0900 Levi Yun wrote: > As ptep_get, Use the pmdp_get wrapper when we accessing pmdval > instead of direct dereferencing pmd. Nit: s/Use/use/ and s/direct/directly > > Signed-off-by: Levi Yun > --- > mm/damon/ops-common.c | 2 +- > mm/damon/paddr.c | 2 +- > mm/damon/vaddr.c | 22 ++++++++++++++-------- > 3 files changed, 16 insertions(+), 10 deletions(-) > > diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c > index e940802a15a4..ac1c3fa80f98 100644 > --- a/mm/damon/ops-common.c > +++ b/mm/damon/ops-common.c > @@ -54,7 +54,7 @@ void damon_ptep_mkold(pte_t *pte, struct vm_area_struct *vma, unsigned long addr > void damon_pmdp_mkold(pmd_t *pmd, struct vm_area_struct *vma, unsigned long addr) > { > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > - struct folio *folio = damon_get_folio(pmd_pfn(*pmd)); > + struct folio *folio = damon_get_folio(pmd_pfn(pmdp_get(pmd))); > > if (!folio) > return; > diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c > index 40801e38fcf0..909db25efb35 100644 > --- a/mm/damon/paddr.c > +++ b/mm/damon/paddr.c > @@ -94,7 +94,7 @@ static bool __damon_pa_young(struct folio *folio, struct vm_area_struct *vma, > mmu_notifier_test_young(vma->vm_mm, addr); > } else { > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > - *accessed = pmd_young(*pvmw.pmd) || > + *accessed = pmd_young(pmdp_get(pvmw.pmd)) || > !folio_test_idle(folio) || > mmu_notifier_test_young(vma->vm_mm, addr); > #else > diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c > index 2fcc9731528a..82f7865719fe 100644 > --- a/mm/damon/vaddr.c > +++ b/mm/damon/vaddr.c > @@ -301,16 +301,19 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, unsigned long addr, > unsigned long next, struct mm_walk *walk) > { > pte_t *pte; > + pmd_t pmde; > spinlock_t *ptl; > > - if (pmd_trans_huge(*pmd)) { > + if (pmd_trans_huge(pmdp_get_lockless(pmd))) { I don't think we really need to use pmdp_get_lockless() here, since we will do this check again with the lock, and we have the fallback for the intermediate changes. > ptl = pmd_lock(walk->mm, pmd); > - if (!pmd_present(*pmd)) { > + pmde = pmdp_get(pmd); > + > + if (!pmd_present(pmde)) { > spin_unlock(ptl); > return 0; > } > > - if (pmd_trans_huge(*pmd)) { > + if (pmd_trans_huge(pmde)) { > damon_pmdp_mkold(pmd, walk->vma, addr); > spin_unlock(ptl); > return 0; > @@ -434,26 +437,29 @@ static int damon_young_pmd_entry(pmd_t *pmd, unsigned long addr, > { > pte_t *pte; > pte_t ptent; > + pmd_t pmde; This would cause below build warning if CONFIG_TRANSPARENT_HUGEPAGE is not defined. .../mm/damon/vaddr.c:440:8: warning: unused variable 'pmde' [-Wunused-variable] 440 | pmd_t pmde; | ^~~~ > spinlock_t *ptl; > struct folio *folio; > struct damon_young_walk_private *priv = walk->private; > > #ifdef CONFIG_TRANSPARENT_HUGEPAGE > - if (pmd_trans_huge(*pmd)) { > + if (pmd_trans_huge(pmdp_get_lockless(pmd))) { Again, pmdp_get() might be enough? > ptl = pmd_lock(walk->mm, pmd); > - if (!pmd_present(*pmd)) { > + pmde = pmdp_get(pmd); > + > + if (!pmd_present(pmde)) { > spin_unlock(ptl); > return 0; > } > > - if (!pmd_trans_huge(*pmd)) { > + if (!pmd_trans_huge(pmde)) { > spin_unlock(ptl); > goto regular_page; > } > - folio = damon_get_folio(pmd_pfn(*pmd)); > + folio = damon_get_folio(pmd_pfn(pmde)); > if (!folio) > goto huge_out; > - if (pmd_young(*pmd) || !folio_test_idle(folio) || > + if (pmd_young(pmde) || !folio_test_idle(folio) || > mmu_notifier_test_young(walk->mm, > addr)) > priv->young = true; > -- > 2.37.2 > Thanks, SJ