From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754427AbcKUMe6 (ORCPT ); Mon, 21 Nov 2016 07:34:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59502 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754073AbcKUMe5 (ORCPT ); Mon, 21 Nov 2016 07:34:57 -0500 Date: Mon, 21 Nov 2016 07:34:52 -0500 From: Jerome Glisse To: Anshuman Khandual Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, John Hubbard , Dan Williams , Ross Zwisler Subject: Re: [HMM v13 04/18] mm/ZONE_DEVICE/free-page: callback when page is freed Message-ID: <20161121123451.GD2392@redhat.com> References: <1479493107-982-1-git-send-email-jglisse@redhat.com> <1479493107-982-5-git-send-email-jglisse@redhat.com> <5832AF9A.8020808@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5832AF9A.8020808@linux.vnet.ibm.com> User-Agent: Mutt/1.7.1 (2016-10-04) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Mon, 21 Nov 2016 12:34:56 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 21, 2016 at 01:56:02PM +0530, Anshuman Khandual wrote: > 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. > I wanted to avoid adding more argument to devm_memremap_pages() as it already has a long list. Hence why i let the caller set those afterward. Cheers, Jérôme