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 X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4AD49C433ED for ; Sun, 25 Apr 2021 02:38:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D62B61245 for ; Sun, 25 Apr 2021 02:38:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229994AbhDYCjF (ORCPT ); Sat, 24 Apr 2021 22:39:05 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:16154 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229514AbhDYCjE (ORCPT ); Sat, 24 Apr 2021 22:39:04 -0400 Received: from DGGEMS411-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4FSXF3728gzpbTJ; Sun, 25 Apr 2021 10:35:19 +0800 (CST) Received: from huawei.com (10.175.104.174) by DGGEMS411-HUB.china.huawei.com (10.3.19.211) with Microsoft SMTP Server id 14.3.498.0; Sun, 25 Apr 2021 10:38:18 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , Subject: [PATCH v4 3/4] mm/swap: remove confusing checking for non_swap_entry() in swap_ra_info() Date: Sun, 25 Apr 2021 10:38:05 +0800 Message-ID: <20210425023806.3537283-4-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20210425023806.3537283-1-linmiaohe@huawei.com> References: <20210425023806.3537283-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.174] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The non_swap_entry() was used for working with VMA based swap readahead via commit ec560175c0b6 ("mm, swap: VMA based swap readahead"). At that time, the non_swap_entry() checking is necessary because the function is called before checking that in do_swap_page(). Then it's moved to swap_ra_info() since commit eaf649ebc3ac ("mm: swap: clean up swap readahead"). After that, the non_swap_entry() checking is unnecessary, because swap_ra_info() is called after non_swap_entry() has been checked already. The resulting code is confusing as the non_swap_entry() check looks racy now because while we released the pte lock, somebody else might have faulted in this pte. So we should check whether it's swap pte first to guard against such race or swap_type will be unexpected. But the race isn't important because it will not cause problem. We would have enough checking when we really operate the PTE entries later. So we remove the non_swap_entry() check here to avoid confusion. Signed-off-by: Miaohe Lin --- mm/swap_state.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/mm/swap_state.c b/mm/swap_state.c index 272ea2108c9d..df5405384520 100644 --- a/mm/swap_state.c +++ b/mm/swap_state.c @@ -721,7 +721,6 @@ static void swap_ra_info(struct vm_fault *vmf, { struct vm_area_struct *vma = vmf->vma; unsigned long ra_val; - swp_entry_t entry; unsigned long faddr, pfn, fpfn; unsigned long start, end; pte_t *pte, *orig_pte; @@ -739,11 +738,6 @@ static void swap_ra_info(struct vm_fault *vmf, faddr = vmf->address; orig_pte = pte = pte_offset_map(vmf->pmd, faddr); - entry = pte_to_swp_entry(*pte); - if ((unlikely(non_swap_entry(entry)))) { - pte_unmap(orig_pte); - return; - } fpfn = PFN_DOWN(faddr); ra_val = GET_SWAP_RA_VAL(vma); -- 2.19.1