From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751831AbcF0FvU (ORCPT ); Mon, 27 Jun 2016 01:51:20 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56823 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751664AbcF0FvT (ORCPT ); Mon, 27 Jun 2016 01:51:19 -0400 X-IBM-Helo: d28dlp02.in.ibm.com X-IBM-MailFrom: khandual@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Mon, 27 Jun 2016 11:21:01 +0530 From: Anshuman Khandual User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Minchan Kim , Anshuman Khandual CC: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Rik van Riel , Vlastimil Babka , Joonsoo Kim , Mel Gorman , Hugh Dickins , Rafael Aquini , virtualization@lists.linux-foundation.org, Jonathan Corbet , John Einar Reitan , dri-devel@lists.freedesktop.org, Sergey Senozhatsky , Gioh Kim Subject: Re: [PATCH v6v3 02/12] mm: migrate: support non-lru movable page migration References: <1463754225-31311-1-git-send-email-minchan@kernel.org> <1463754225-31311-3-git-send-email-minchan@kernel.org> <20160530013926.GB8683@bbox> <20160531000117.GB18314@bbox> <575E7F0B.8010201@linux.vnet.ibm.com> <20160615023249.GG17127@bbox> <5760F970.7060805@linux.vnet.ibm.com> <20160616002617.GM17127@bbox> <5762200F.5040908@linux.vnet.ibm.com> <20160616053754.GQ17127@bbox> In-Reply-To: <20160616053754.GQ17127@bbox> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16062705-4789-0000-0000-000002D9B6CD X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16062705-4790-0000-0000-00001095F1C3 Message-Id: <5770BEC5.3010807@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-27_03:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1606270066 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/16/2016 11:07 AM, Minchan Kim wrote: > On Thu, Jun 16, 2016 at 09:12:07AM +0530, Anshuman Khandual wrote: >> On 06/16/2016 05:56 AM, Minchan Kim wrote: >>> On Wed, Jun 15, 2016 at 12:15:04PM +0530, Anshuman Khandual wrote: >>>> On 06/15/2016 08:02 AM, Minchan Kim wrote: >>>>> Hi, >>>>> >>>>> On Mon, Jun 13, 2016 at 03:08:19PM +0530, Anshuman Khandual wrote: >>>>>>> On 05/31/2016 05:31 AM, Minchan Kim wrote: >>>>>>>>> @@ -791,6 +921,7 @@ static int __unmap_and_move(struct page *page, struct page *newpage, >>>>>>>>> int rc = -EAGAIN; >>>>>>>>> int page_was_mapped = 0; >>>>>>>>> struct anon_vma *anon_vma = NULL; >>>>>>>>> + bool is_lru = !__PageMovable(page); >>>>>>>>> >>>>>>>>> if (!trylock_page(page)) { >>>>>>>>> if (!force || mode == MIGRATE_ASYNC) >>>>>>>>> @@ -871,6 +1002,11 @@ static int __unmap_and_move(struct page *page, struct page *newpage, >>>>>>>>> goto out_unlock_both; >>>>>>>>> } >>>>>>>>> >>>>>>>>> + if (unlikely(!is_lru)) { >>>>>>>>> + rc = move_to_new_page(newpage, page, mode); >>>>>>>>> + goto out_unlock_both; >>>>>>>>> + } >>>>>>>>> + >>>>>>> >>>>>>> Hello Minchan, >>>>>>> >>>>>>> I might be missing something here but does this implementation support the >>>>>>> scenario where these non LRU pages owned by the driver mapped as PTE into >>>>>>> process page table ? Because the "goto out_unlock_both" statement above >>>>>>> skips all the PTE unmap, putting a migration PTE and removing the migration >>>>>>> PTE steps. >>>>> You're right. Unfortunately, it doesn't support right now but surely, >>>>> it's my TODO after landing this work. >>>>> >>>>> Could you share your usecase? >>>> >>>> Sure. >>> >>> Thanks a lot! >>> >>>> >>>> My driver has privately managed non LRU pages which gets mapped into user space >>>> process page table through f_ops->mmap() and vmops->fault() which then updates >>>> the file RMAP (page->mapping->i_mmap) through page_add_file_rmap(page). One thing >>> >>> Hmm, page_add_file_rmap is not exported function. How does your driver can use it? >> >> Its not using the function directly, I just re-iterated the sequence of functions >> above. (do_set_pte -> page_add_file_rmap) gets called after we grab the page from >> driver through (__do_fault->vma->vm_ops->fault()). >> >>> Do you use vm_insert_pfn? >>> What type your vma is? VM_PFNMMAP or VM_MIXEDMAP? >> >> I dont use vm_insert_pfn(). Here is the sequence of events how the user space >> VMA gets the non LRU pages from the driver. >> >> - Driver registers a character device with 'struct file_operations' binding >> - Then the 'fops->mmap()' just binds the incoming 'struct vma' with a 'struct >> vm_operations_struct' which provides the 'vmops->fault()' routine which >> basically traps all page faults on the VMA and provides one page at a time >> through a driver specific allocation routine which hands over non LRU pages >> >> The VMA is not anything special as such. Its what we get when we try to do a >> simple mmap() on a file descriptor pointing to a character device. I can >> figure out all the VM_* flags it holds after creation. >> >>> >>> I want to make dummy driver to simulate your case. >> >> Sure. I hope the above mentioned steps will help you but in case you need more >> information, please do let me know. > > I got understood now. :) > I will test it with dummy driver and will Cc'ed when I send a patch. Hello Minchan, Do you have any updates on this ? The V7 of the series still has this limitation. Did you get a chance to test the driver out ? I am still concerned about how to handle the struct address_space override problem within the struct page. - Anshuman