From patchwork Sun Apr 25 02:38:05 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12222951 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 AAC24C433B4 for ; Sun, 25 Apr 2021 02:38:31 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0BB0961601 for ; Sun, 25 Apr 2021 02:38:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0BB0961601 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 62C326B0071; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 5D7226B0073; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 435136B0071; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0108.hostedemail.com [216.40.44.108]) by kanga.kvack.org (Postfix) with ESMTP id 238816B0036 for ; Sat, 24 Apr 2021 22:38:30 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C428F18000BF3 for ; Sun, 25 Apr 2021 02:38:29 +0000 (UTC) X-FDA: 78069330738.25.6741B71 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) by imf21.hostedemail.com (Postfix) with ESMTP id 00EE3E000125 for ; Sun, 25 Apr 2021 02:38:25 +0000 (UTC) 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 X-Originating-IP: [10.175.104.174] X-CFilter-Loop: Reflected X-Stat-Signature: sigskzzuzcy18n7adfhw9k4wsccciwee X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 00EE3E000125 Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=szxga04-in.huawei.com; client-ip=45.249.212.190 X-HE-DKIM-Result: none/none X-HE-Tag: 1619318305-230045 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: 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 Reviewed-by: "Huang, Ying" --- 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);