From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 82DBD6B02F2 for ; Fri, 28 Apr 2017 15:16:14 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id o85so15361650qkh.15 for ; Fri, 28 Apr 2017 12:16:14 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id t40si6974412qtb.245.2017.04.28.12.16.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 28 Apr 2017 12:16:13 -0700 (PDT) Date: Fri, 28 Apr 2017 15:16:11 -0400 (EDT) From: Jerome Glisse Message-ID: <1295710462.4327805.1493406971970.JavaMail.zimbra@redhat.com> In-Reply-To: References: <20170428063913.iz6xjcxblecofjlq@gmail.com> <149339998297.24933.1129582806028305912.stgit@dwillia2-desk3.amr.corp.intel.com> <1743017574.4309811.1493400875692.JavaMail.zimbra@redhat.com> <1579714997.4315035.1493402406629.JavaMail.zimbra@redhat.com> Subject: Re: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Linux MM , Ingo Molnar , Andrew Morton , Logan Gunthorpe , Kirill Shutemov > On Fri, Apr 28, 2017 at 11:00 AM, Jerome Glisse wrot= e: > >> On Fri, Apr 28, 2017 at 10:34 AM, Jerome Glisse > >> wrote: > >> >> Kirill points out that the calls to {get,put}_dev_pagemap() can be > >> >> removed from the mm fast path if we take a single get_dev_pagemap() > >> >> reference to signify that the page is alive and use the final put o= f > >> >> the > >> >> page to drop that reference. > >> >> > >> >> This does require some care to make sure that any waits for the > >> >> percpu_ref to drop to zero occur *after* devm_memremap_page_release= (), > >> >> since it now maintains its own elevated reference. > >> > > >> > This is NAK from HMM point of view as i need those call. So if you > >> > remove > >> > them now i will need to add them back as part of HMM. > >> > >> I thought you only need them at page free time? You can still hook > >> __put_page(). > > > > No, i need a hook when page refcount reach 1, not 0. That being said > > i don't care about put_dev_pagemap(page->pgmap); so that part of the > > patch is fine from HMM point of view but i definitly need to hook my- > > self in the general put_page() function. > > > > So i will have to undo part of this patch for HMM (put_page() will > > need to handle ZONE_DEVICE page differently). >=20 > Ok, I'd rather this go in now since it fixes the existing use case, > and unblocks the get_user_pages_fast() conversion to generic code. > That also gives Kirill and -mm folks a chance to review what HMM wants > to do on top of the page_ref infrastructure. The > {get,put}_zone_device_page interface went in in 4.5 right before > page_ref went in during 4.6, so it was just an oversight that > {get,put}_zone_device_page were not removed earlier. >=20 I don't mind this going in, i am hopping people won't ignore HMM patchset once i repost after 4.12 merge window. Note that there is absolutely no way around me hooking up inside put_page(). The only other way to do it would be to modify virtualy all places that call that function to handle ZONE_DEV= ICE case. J=C3=A9r=C3=B4me -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org