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 83263C2BA83 for ; Fri, 14 Feb 2020 17:41:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60309206B6 for ; Fri, 14 Feb 2020 17:41:29 +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="VCS5visr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728895AbgBNRl3 (ORCPT ); Fri, 14 Feb 2020 12:41:29 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:33430 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389712AbgBNQDm (ORCPT ); Fri, 14 Feb 2020 11:03:42 -0500 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=vWvhCkmP10pOefEokptjf5gNpQByGXrHCLm2fjpQLRQ=; b=VCS5visrKpAL+Ru5FY/G0h94PF MRs9RZXEy+XhvvLBu4HzE+Ed33L6Z0f2KGHW7sJVb06H30RZt6ZdaFnl4TIHuT+93DBWIdiEkdl12 VyGaJAUCFsfCeiNV0jSSN4Lz7qORyUBqbLb/AraVAK+XDJgVeTipoyvmuMDWCzqpmBLE1JAqt/HAc Y1hrahhKXOY3jcxwcCxFt9iofsSXg9l5AW6BNd/82HfepDdNRDi1Vtj3TioDDl+oenDnmaflYS4NT eN3yRu+nLR5BBbhfQryyJ7xcU9/53ByshYrmJL2RtsfJb6QOkdsVKfp2AvvokNsEL5MZd2vn5Qt/n V/xyxDOw==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j2dRO-00022S-7n; Fri, 14 Feb 2020 16:03:42 +0000 Date: Fri, 14 Feb 2020 08:03:42 -0800 From: Matthew Wilcox To: "Kirill A. Shutemov" Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 13/25] fs: Add zero_user_large Message-ID: <20200214160342.GA7778@bombadil.infradead.org> References: <20200212041845.25879-1-willy@infradead.org> <20200212041845.25879-14-willy@infradead.org> <20200214135248.zqcqx3erb4pnlvmu@box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200214135248.zqcqx3erb4pnlvmu@box> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 14, 2020 at 04:52:48PM +0300, Kirill A. Shutemov wrote: > On Tue, Feb 11, 2020 at 08:18:33PM -0800, Matthew Wilcox wrote: > > From: "Matthew Wilcox (Oracle)" > > > > We can't kmap() a THP, so add a wrapper around zero_user() for large > > pages. > > I would rather address it closer to the root: make zero_user_segments() > handle compound pages. Hah. I ended up doing that, but hadn't sent it out. I don't like how ugly it is: @@ -219,18 +219,57 @@ static inline void zero_user_segments(struct page *page, unsigned start1, unsigned end1, unsigned start2, unsigned end2) { - void *kaddr = kmap_atomic(page); - - BUG_ON(end1 > PAGE_SIZE || end2 > PAGE_SIZE); - - if (end1 > start1) - memset(kaddr + start1, 0, end1 - start1); - - if (end2 > start2) - memset(kaddr + start2, 0, end2 - start2); - - kunmap_atomic(kaddr); - flush_dcache_page(page); + unsigned int i; + + BUG_ON(end1 > thp_size(page) || end2 > thp_size(page)); + + for (i = 0; i < hpage_nr_pages(page); i++) { + void *kaddr; + unsigned this_end; + + if (end1 == 0 && start2 >= PAGE_SIZE) { + start2 -= PAGE_SIZE; + end2 -= PAGE_SIZE; + continue; + } + + if (start1 >= PAGE_SIZE) { + start1 -= PAGE_SIZE; + end1 -= PAGE_SIZE; + if (start2) { + start2 -= PAGE_SIZE; + end2 -= PAGE_SIZE; + } + continue; + } + + kaddr = kmap_atomic(page + i); + + this_end = min_t(unsigned, end1, PAGE_SIZE); + if (end1 > start1) + memset(kaddr + start1, 0, this_end - start1); + end1 -= this_end; + start1 = 0; + + if (start2 >= PAGE_SIZE) { + start2 -= PAGE_SIZE; + end2 -= PAGE_SIZE; + } else { + this_end = min_t(unsigned, end2, PAGE_SIZE); + if (end2 > start2) + memset(kaddr + start2, 0, this_end - start2); + end2 -= this_end; + start2 = 0; + } + + kunmap_atomic(kaddr); + flush_dcache_page(page + i); + + if (!end1 && !end2) + break; + } + + BUG_ON((start1 | start2 | end1 | end2) != 0); } I think at this point it has to move out-of-line too. > > +static inline void zero_user_large(struct page *page, > > + unsigned start, unsigned size) > > +{ > > + unsigned int i; > > + > > + for (i = 0; i < thp_order(page); i++) { > > + if (start > PAGE_SIZE) { > > Off-by-one? >= ? Good catch; I'd also noticed that when I came to redo the zero_user_segments().