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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 26832C43217 for ; Thu, 12 May 2022 23:39:08 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8A92F6B0073; Thu, 12 May 2022 19:39:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 858286B0075; Thu, 12 May 2022 19:39:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 720506B0078; Thu, 12 May 2022 19:39:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 62D1F6B0073 for ; Thu, 12 May 2022 19:39:07 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 29169804B3 for ; Thu, 12 May 2022 23:39:07 +0000 (UTC) X-FDA: 79458709134.26.5598FBC Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf31.hostedemail.com (Postfix) with ESMTP id 3D38C200A8 for ; Thu, 12 May 2022 23:38:43 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 10319B82BBA; Thu, 12 May 2022 23:39:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 79DAEC34114; Thu, 12 May 2022 23:39:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1652398743; bh=a3XDOUB9VZEdL/qmAz+db5Tw1Rvx5NWZ7c0BuRE+hCg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gg1eeorwkof0x/0Hw7YyFEZpnqETBiwE7FCiOYkigQwowSQ/8oEusNpkCbwG1Vbtk lULYu4bYk6NL70MOvNMOYaKBbsIubBEGlf0JfIjQRJ2jJPVbe4eNRnvbByub5RtgCw dGGMiB5aTE/5ua3LEOdd/I6VgisrGIEA7GamCkk4= Date: Thu, 12 May 2022 16:39:02 -0700 From: Andrew Morton To: Yang Shi Cc: willy@infradead.org, songmuchun@bytedance.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: pvmw: check possible huge PMD map by transhuge_vma_suitable() Message-Id: <20220512163902.5e128f6dd5dd6e44afa53259@linux-foundation.org> In-Reply-To: <20220512174551.81279-2-shy828301@gmail.com> References: <20220512174551.81279-1-shy828301@gmail.com> <20220512174551.81279-2-shy828301@gmail.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 3D38C200A8 Authentication-Results: imf31.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=gg1eeorw; spf=pass (imf31.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Rspam-User: X-Stat-Signature: djehz6yb38hzdeid6tqe9jgjm4shfz6c X-HE-Tag: 1652398723-312579 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: On Thu, 12 May 2022 10:45:51 -0700 Yang Shi wrote: > IIUC PVMW checks if the vma is possibly huge PMD mapped by > transparent_hugepage_active() and "pvmw->nr_pages >= HPAGE_PMD_NR". > > Actually pvmw->nr_pages is returned by compound_nr() or > folio_nr_pages(), so the page should be THP as long as "pvmw->nr_pages > >= HPAGE_PMD_NR". And it is guaranteed THP is allocated for valid VMA > in the first place. But it may be not PMD mapped if the VMA is file > VMA and it is not properly aligned. The transhuge_vma_suitable() > is used to do such check, so replace transparent_hugepage_active() to > it, which is too heavy and overkilling. > > ... > > --- a/mm/page_vma_mapped.c > +++ b/mm/page_vma_mapped.c > @@ -237,13 +237,14 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) > spin_unlock(pvmw->ptl); > pvmw->ptl = NULL; > } else if (!pmd_present(pmde)) { > + unsigned long haddr = pvmw->address & HPAGE_PMD_MASK; This hits #define HPAGE_PMD_MASK ({ BUILD_BUG(); 0; }) when CONFIG_TRANSPARENT_HUGEPAGE=n (x86_64 allnoconfig).