Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752580AbcKUI0Q (ORCPT ); Mon, 21 Nov 2016 03:26:16 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:57367 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751783AbcKUI0O (ORCPT ); Mon, 21 Nov 2016 03:26:14 -0500 Subject: Re: [HMM v13 04/18] mm/ZONE_DEVICE/free-page: callback when page is freed To: =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <1479493107-982-1-git-send-email-jglisse@redhat.com> <1479493107-982-5-git-send-email-jglisse@redhat.com> Cc: John Hubbard , Dan Williams , Ross Zwisler From: Anshuman Khandual Date: Mon, 21 Nov 2016 13:56:02 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1479493107-982-5-git-send-email-jglisse@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16112108-0032-0000-0000-0000018ACA51 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16112108-0033-0000-0000-000010E31B9F Message-Id: <5832AF9A.8020808@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-11-21_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=2 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1609300000 definitions=main-1611210151 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2690 Lines: 68 On 11/18/2016 11:48 PM, Jérôme Glisse wrote: > When a ZONE_DEVICE page refcount reach 1 it means it is free and nobody > is holding a reference on it (only device to which the memory belong do). > Add a callback and call it when that happen so device driver can implement > their own free page management. > > Signed-off-by: Jérôme Glisse > Cc: Dan Williams > Cc: Ross Zwisler > --- > include/linux/memremap.h | 4 ++++ > kernel/memremap.c | 8 ++++++++ > 2 files changed, 12 insertions(+) > > diff --git a/include/linux/memremap.h b/include/linux/memremap.h > index fe61dca..469c88d 100644 > --- a/include/linux/memremap.h > +++ b/include/linux/memremap.h > @@ -37,17 +37,21 @@ static inline struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start) > > /** > * struct dev_pagemap - metadata for ZONE_DEVICE mappings > + * @free_devpage: free page callback when page refcount reach 1 > * @altmap: pre-allocated/reserved memory for vmemmap allocations > * @res: physical address range covered by @ref > * @ref: reference count that pins the devm_memremap_pages() mapping > * @dev: host device of the mapping for debug > + * @data: privata data pointer for free_devpage > * @flags: memory flags (look for MEMORY_FLAGS_NONE in memory_hotplug.h) > */ > struct dev_pagemap { > + void (*free_devpage)(struct page *page, void *data); > struct vmem_altmap *altmap; > const struct resource *res; > struct percpu_ref *ref; > struct device *dev; > + void *data; > int flags; > }; > > diff --git a/kernel/memremap.c b/kernel/memremap.c > index 438a73aa2..3d28048 100644 > --- a/kernel/memremap.c > +++ b/kernel/memremap.c > @@ -190,6 +190,12 @@ EXPORT_SYMBOL(get_zone_device_page); > > void put_zone_device_page(struct page *page) > { > + /* > + * If refcount is 1 then page is freed and refcount is stable as nobody > + * holds a reference on the page. > + */ > + if (page->pgmap->free_devpage && page_count(page) == 1) > + page->pgmap->free_devpage(page, page->pgmap->data); > put_dev_pagemap(page->pgmap); > } > EXPORT_SYMBOL(put_zone_device_page); > @@ -326,6 +332,8 @@ void *devm_memremap_pages(struct device *dev, struct resource *res, > pgmap->ref = ref; > pgmap->res = &page_map->res; > pgmap->flags = flags | MEMORY_DEVICE; > + pgmap->free_devpage = NULL; > + pgmap->data = NULL; When is the driver expected to load up pgmap->free_devpage ? I thought this function is one of the right places. Though as all the pages in the same hotplug operation point to the same dev_pagemap structure this loading can be done at later point of time as well.