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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 AAEF3C47254 for ; Fri, 1 May 2020 22:48:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 60A21208D6 for ; Fri, 1 May 2020 22:48:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="qXb1AUxF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60A21208D6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id F08C18E0005; Fri, 1 May 2020 18:48:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E90D08E0001; Fri, 1 May 2020 18:48:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D7F458E0005; Fri, 1 May 2020 18:48:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0125.hostedemail.com [216.40.44.125]) by kanga.kvack.org (Postfix) with ESMTP id BCD588E0001 for ; Fri, 1 May 2020 18:48:55 -0400 (EDT) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 772938248047 for ; Fri, 1 May 2020 22:48:55 +0000 (UTC) X-FDA: 76769641830.20.quilt68_30c4c55033026 X-HE-Tag: quilt68_30c4c55033026 X-Filterd-Recvd-Size: 2349 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Fri, 1 May 2020 22:48:55 +0000 (UTC) Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2CA7C208D6; Fri, 1 May 2020 22:48:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588373334; bh=+8ojglKGEmkO9iB05BMBJhMJkf9Z5gTGUig9zB2BCYk=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qXb1AUxFwf8SfiVD1hp1KVtxCVgLHhwERL3lbJCOXqQdCh2GuFvS/26htkilGQR4D ++9T85SXIC7GxJxaRwnLa1L0MH/Y+nuC+D6+lklVCuVQnC3GRBL+d9Te+eu784JxhI WoRVqqX4yFb7Rm5cXWyKbQzt3ZUpRasuhXHC/DBY= Date: Fri, 1 May 2020 15:48:53 -0700 From: Andrew Morton To: Wei Yang Cc: ying.huang@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 3/3] mm/swapfile.c: count won't be bigger than SWAP_MAP_MAX Message-Id: <20200501154853.bca4cfb7b2558bd43a4942f3@linux-foundation.org> In-Reply-To: <20200501015259.32237-3-richard.weiyang@gmail.com> References: <20200501015259.32237-1-richard.weiyang@gmail.com> <20200501015259.32237-3-richard.weiyang@gmail.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000293, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, 1 May 2020 01:52:59 +0000 Wei Yang wrote: > When the condition is true, there are two possibilities: I'm struggling with this one. > 1. count == SWAP_MAP_BAD > 2. count == (SWAP_MAP_MAX & COUNT_CONTINUED) == SWAP_MAP_SHMEM I'm not sure what 2. is trying to say. For a start, (SWAP_MAP_MAX & COUNT_CONTINUED) is zero. I guess it meant "|"? Also, the return value documentation says we return EINVAL for migration entries. Where's that happening, or is the comment out of date? > The first case would be filtered by the first if in __swap_duplicate(). > > And the second case means this swap entry is for shmem. Since we never > do another duplication for shmem swap entry. This won't happen neither.