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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95A2BCCA47C for ; Wed, 29 Jun 2022 23:31:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230447AbiF2Xbe (ORCPT ); Wed, 29 Jun 2022 19:31:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229821AbiF2Xbc (ORCPT ); Wed, 29 Jun 2022 19:31:32 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C873625C; Wed, 29 Jun 2022 16:31:31 -0700 (PDT) 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 dfw.source.kernel.org (Postfix) with ESMTPS id 6BD11614D9; Wed, 29 Jun 2022 23:31:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5AD79C34114; Wed, 29 Jun 2022 23:31:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1656545490; bh=EUtoD6mxDI6S48VU4JnwbI++d7sfQ0Ba+nGXTEVn3jI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ko/bDBvXxEcl48eumHeFgpRmNjd7wuaH7G0qP1t6sIobV5qNgwt9GvaQkmQ+8dLZe hKn2EQAupvKSihpNA1xULMkEVgDQpKd2GPIe2XSS8++/sO3ZQjzDOdGljxu/viVmyv Z6MSvOI4xrcShSRXxM7iYVplJ7VEnCGXQnVIYp5g= Date: Wed, 29 Jun 2022 16:31:28 -0700 From: Andrew Morton To: David Hildenbrand Cc: Alex Sierra , jgg@nvidia.com, Felix.Kuehling@amd.com, linux-mm@kvack.org, rcampbell@nvidia.com, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, hch@lst.de, jglisse@redhat.com, apopple@nvidia.com, willy@infradead.org Subject: Re: [PATCH v7 03/14] mm: handling Non-LRU pages returned by vm_normal_pages Message-Id: <20220629163128.7002f81b6346b2ed34d4d02a@linux-foundation.org> In-Reply-To: <269e4c6e-d6ee-bace-9fab-a9dcb4268d5a@redhat.com> References: <20220629035426.20013-1-alex.sierra@amd.com> <20220629035426.20013-4-alex.sierra@amd.com> <269e4c6e-d6ee-bace-9fab-a9dcb4268d5a@redhat.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 Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Wed, 29 Jun 2022 11:59:26 +0200 David Hildenbrand wrote: > On 29.06.22 05:54, Alex Sierra wrote: > > With DEVICE_COHERENT, we'll soon have vm_normal_pages() return > > device-managed anonymous pages that are not LRU pages. Although they > > behave like normal pages for purposes of mapping in CPU page, and for > > COW. They do not support LRU lists, NUMA migration or THP. > > > > Callers to follow_page that expect LRU pages, are also checked for > > device zone pages due to DEVICE_COHERENT type. > > Can we rephrase that to (because zeropage) > > "Callers to follow_page() currently don't expect ZONE_DEVICE pages, > however, with DEVICE_COHERENT we might now return ZONE_DEVICE. Check for > ZONE_DEVICE pages in applicable users of follow_page() as well." I made that change to my copy. > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -624,6 +624,13 @@ struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr, > > if (is_zero_pfn(pfn)) > > return NULL; > > if (pte_devmap(pte)) > > +/* > > + * NOTE: New uers of ZONE_DEVICE will not set pte_devmap() and will have > > s/uers/users/ > > > + * refcounts incremented on their struct pages when they are inserted into > > + * PTEs, thus they are safe to return here. Legacy ZONE_DEVICE pages that set > > + * pte_devmap() do not have refcounts. Example of legacy ZONE_DEVICE is > > + * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers. > > + */ And let's regularize that comment placement? --- a/mm/memory.c~mm-handling-non-lru-pages-returned-by-vm_normal_pages-fix +++ a/mm/memory.c @@ -632,16 +632,16 @@ struct page *vm_normal_page(struct vm_ar return NULL; if (is_zero_pfn(pfn)) return NULL; + /* + * NOTE: New users of ZONE_DEVICE will not set pte_devmap() + * and will have refcounts incremented on their struct pages + * when they are inserted into PTEs, thus they are safe to + * return here. Legacy ZONE_DEVICE pages that set pte_devmap() + * do not have refcounts. Example of legacy ZONE_DEVICE is + * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers. + */ if (pte_devmap(pte)) -/* - * NOTE: New uers of ZONE_DEVICE will not set pte_devmap() and will have - * refcounts incremented on their struct pages when they are inserted into - * PTEs, thus they are safe to return here. Legacy ZONE_DEVICE pages that set - * pte_devmap() do not have refcounts. Example of legacy ZONE_DEVICE is - * MEMORY_DEVICE_FS_DAX type in pmem or virtio_fs drivers. - */ return NULL; - print_bad_pte(vma, addr, pte, NULL); return NULL; } _