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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 5428CC433E2 for ; Thu, 28 May 2020 11:45:22 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 19A83208A7 for ; Thu, 28 May 2020 11:45:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="kHKRiNyV" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 19A83208A7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 9AD0B8001A; Thu, 28 May 2020 07:45:21 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 95D1880010; Thu, 28 May 2020 07:45:21 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 873CF8001A; Thu, 28 May 2020 07:45:21 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0141.hostedemail.com [216.40.44.141]) by kanga.kvack.org (Postfix) with ESMTP id 6D45280010 for ; Thu, 28 May 2020 07:45:21 -0400 (EDT) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 22E45181AEF15 for ; Thu, 28 May 2020 11:45:21 +0000 (UTC) X-FDA: 76865947242.16.back99_2e3325829ef4c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id 03483100E690B for ; Thu, 28 May 2020 11:45:20 +0000 (UTC) X-HE-Tag: back99_2e3325829ef4c X-Filterd-Recvd-Size: 2221 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 28 May 2020 11:45:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=DS37L5ALyvZ+2WWVFgwjUsVIkQm7OFYuedyteB9C0KM=; b=kHKRiNyVv6w/tyjgm1SR+C90PP +RU55kYVdrXv2Vt1gjMwhuIpZjkM6ddaaqGCwcFhUlznLEGK7lrBWwDMI5Zxjyc+vM0lEKKUFmPy4 ZFYUZfpnHrlNeVnEys7zysIf8+6AdvsxtXiWfs5MbgW10YEbsrpUkZo3yVqopV2HNFifKvdqADN0x tAw7saZm3Y5QPcmjqMjxKsk+vDcuLP6BJa7IsdqKBqj3sKDewe7jQJ/wZ2GP1OE1pA1mYqPVWxvI+ I2U2n0k2hnlqHf9ttAU/Q2/4KmxQPUvK3h5TFWk+ElREUPD4AtCcReFOfmh9QZtYyXCWGoY0md9SJ wYl3U5CQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jeGyJ-0003p5-Pj; Thu, 28 May 2020 11:45:15 +0000 Date: Thu, 28 May 2020 04:45:15 -0700 From: Matthew Wilcox To: hui yang Cc: akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH] mm page_fault: Reduce code complexity Message-ID: <20200528114515.GO17206@bombadil.infradead.org> References: <1590663699-4541-1-git-send-email-yanghui.def@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1590663699-4541-1-git-send-email-yanghui.def@gmail.com> X-Rspamd-Queue-Id: 03483100E690B X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 X-Bogosity: Ham, tests=bogofilter, spamicity=0.016234, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, May 28, 2020 at 07:01:39PM +0800, hui yang wrote: > From: YangHui > > if pte_alloc_one failed alloc a page, do_fault_around will return 0. > and it will come into __do_fault(), it also pte_alloc_one a page. > in __do_fault and do_fault_around, pte_alloc_one did the same thing, > if do_fault_around alloc page filed,we just let it return. there is > no need to come into __do_fault to do repetitive pte_alloc_one. This really isn't "Reduce code complexity" though. It's "Fail early when memory allocation fails". And, honestly, I don't see the point of doing this. You've optimised an incredibly rare failure path.