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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 89FCFC43461 for ; Thu, 3 Sep 2020 16:39:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4A24520775 for ; Thu, 3 Sep 2020 16:39:05 +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="t+KqJCDI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4A24520775 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 DC5888E0003; Thu, 3 Sep 2020 12:39:04 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D9E1C8E0001; Thu, 3 Sep 2020 12:39:04 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id CDABB8E0003; Thu, 3 Sep 2020 12:39:04 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0209.hostedemail.com [216.40.44.209]) by kanga.kvack.org (Postfix) with ESMTP id B9AFD8E0001 for ; Thu, 3 Sep 2020 12:39:04 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7D7DE8248076 for ; Thu, 3 Sep 2020 16:39:04 +0000 (UTC) X-FDA: 77222309808.28.gold99_2004cfd270ab Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin28.hostedemail.com (Postfix) with ESMTP id 379C56C04 for ; Thu, 3 Sep 2020 16:39:04 +0000 (UTC) X-HE-Tag: gold99_2004cfd270ab X-Filterd-Recvd-Size: 2711 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf11.hostedemail.com (Postfix) with ESMTP for ; Thu, 3 Sep 2020 16:39:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=GYkytVJ3w8/QX0GH4bMirJqpdv8hdhcNl96xhFqD6Zw=; b=t+KqJCDIRe8WMa6NMkknPczheE xcoqpwz0ZzMDtXOnHe2WhI9E/F7bVNoeI80txM/bVe45QWF60ND3yqlES4OZcjh/2WlTQYwBtLR8d 0bs/d2C/KDOOPKAxFJzADyf+DbJ0DTx5UT9rgACbGy7btKXWtflnmDeOtoFw6znD40w9luewjtQFQ cUEiogmat2aLyh3dtnRQwaHQdmahfD6RSujQjFLAI48uqqXKR5yAVwcbksHBOoi7UIDuAkzvfBQIm 5P7MUOuvuAmz85/HI36BD2XJumuV4C8Tv5e6vthhkIVK/kQNesFI/Q3kS/YeoySXpGkMNNgg4xlBz /41Ug7xg==; Received: from hch by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDsGG-0005Rb-LC; Thu, 03 Sep 2020 16:38:56 +0000 Date: Thu, 3 Sep 2020 17:38:56 +0100 From: Christoph Hellwig To: Robin Murphy Cc: joro@8bytes.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Roman Gushchin Subject: Re: [PATCH] iommu/dma: Remove broken huge page handling Message-ID: <20200903163856.GA20737@infradead.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html X-Rspamd-Queue-Id: 379C56C04 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam02 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Sep 03, 2020 at 12:34:04PM +0100, Robin Murphy wrote: > The attempt to handle huge page allocations was originally added since > the comments around stripping __GFP_COMP in other implementations were > nonsensical, and we naively assumed that split_huge_page() could simply > be called equivalently to split_page(). It turns out that this doesn't > actually work correctly, so just get rid of it - there's little point > going to the effort of allocating huge pages if we're only going to > split them anyway. > > Reported-by: Roman Gushchin > Signed-off-by: Robin Murphy This looks sensibe. We really need to clear it in generic code, but last time I checked there were one or two buggy drivers that assumed __GFP_COMP works and actually gives a compound page (iirc legacy drm stuff). All that stuff really needs fixing.. Reviewed-by: Christoph Hellwig