From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-x244.google.com (mail-oi0-x244.google.com [IPv6:2607:f8b0:4003:c06::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 6F0A4224488AE for ; Mon, 12 Mar 2018 11:11:06 -0700 (PDT) Received: by mail-oi0-x244.google.com with SMTP id x12so13111253oie.13 for ; Mon, 12 Mar 2018 11:17:27 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20180312141721.GB4214@redhat.com> References: <152066488891.40260.14605734226832760468.stgit@dwillia2-desk3.amr.corp.intel.com> <152066492680.40260.6843692416565308005.stgit@dwillia2-desk3.amr.corp.intel.com> <20180312141721.GB4214@redhat.com> From: Dan Williams Date: Mon, 12 Mar 2018 11:17:25 -0700 Message-ID: Subject: Re: [PATCH v5 07/11] mm, dev_pagemap: introduce CONFIG_DEV_PAGEMAP_OPS List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: Jerome Glisse Cc: Michal Hocko , Jan Kara , linux-nvdimm , david , Linux Kernel Mailing List , linux-xfs , linux-fsdevel , Christoph Hellwig List-ID: T24gTW9uLCBNYXIgMTIsIDIwMTggYXQgNzoxNyBBTSwgSmVyb21lIEdsaXNzZSA8amdsaXNzZUBy ZWRoYXQuY29tPiB3cm90ZToKPiBPbiBGcmksIE1hciAwOSwgMjAxOCBhdCAxMDo1NToyNlBNIC0w ODAwLCBEYW4gV2lsbGlhbXMgd3JvdGU6Cj4+IFRoZSBITU0gc3ViLXN5c3RlbSBleHRlbmRlZCBk ZXZfcGFnZW1hcCB0byBhcnJhbmdlIGEgY2FsbGJhY2sgd2hlbiBhCj4+IGRldl9wYWdlbWFwIG1h bmFnZWQgcGFnZSBpcyBmcmVlZC4gU2luY2UgYSBkZXZfcGFnZW1hcCBwYWdlIGlzIGZyZWUgLwo+ PiBpZGxlIHdoZW4gaXRzIHJlZmVyZW5jZSBjb3VudCBpcyAxIGl0IHJlcXVpcmVzIGFuIGFkZGl0 aW9uYWwgYnJhbmNoIHRvCj4+IGNoZWNrIHRoZSBwYWdlLXR5cGUgYXQgcHV0X3BhZ2UoKSB0aW1l LiBHaXZlbiBwdXRfcGFnZSgpIGlzIGEgaG90LXBhdGgKPj4gd2UgZG8gbm90IHdhbnQgdG8gaW5j dXIgdGhhdCBjaGVjayBpZiBITU0gaXMgbm90IGluIHVzZSwgc28gYSBzdGF0aWMKPj4gYnJhbmNo IGlzIHVzZWQgdG8gYXZvaWQgdGhhdCBvdmVyaGVhZCB3aGVuIG5vdCBuZWNlc3NhcnkuCj4+Cj4+ IE5vdywgdGhlIEZTX0RBWCBpbXBsZW1lbnRhdGlvbiB3YW50cyB0byByZXVzZSB0aGlzIG1lY2hh bmlzbSBmb3IKPj4gcmVjZWl2aW5nIGRldl9wYWdlbWFwIC0+cGFnZV9mcmVlKCkgY2FsbGJhY2tz LiBSZXdvcmsgdGhlIEhNTS1zcGVjaWZpYwo+PiBzdGF0aWMta2V5IGludG8gYSBnZW5lcmljIG1l Y2hhbmlzbSB0aGF0IGVpdGhlciBITU0gb3IgRlNfREFYIGNvZGUgcGF0aHMKPj4gY2FuIGVuYWJs ZS4KPgo+IFdoeSBFWFBPUlRfU1lNQk9MX0dQTCBhbmQgbm90IEVYUE9SVF9TWU1CT0wgbGlrZSBp dCB3YXMgcHJpb3IgdG8gdGhpcwo+IHBhdGNoID8gTm90IGkgY2FyZSB0aGF0IG11Y2ggYWJvdXQg dGhhdCwganVzdCB3b25kZXJpbmcuIE1heWJlIGtlZXAgaXQKPiBFWFBPUlRfU1lNQk9MKCkgPwoK SE1NIGhhcyBzaWduaWZpY2FudCBpbnRlZ3JhdGlvbnMgYW5kIHVzZWZ1bCBoYWNrcyB3aXRoaW4g dGhlIG1tCnN1Yi1zeXN0ZW0sIEkgdGhpbmsgd2Ugc2hvdWxkIGdvIGZ1cnRoZXIgdGhhbiBqdXN0 IHRoZXNlIHN5bWJvbHMgYW5kCmFsc28gaW5jbHVkZSBkZXZtX21lbXJlbWFwX3BhZ2VzKCkgYXMg RVhQT1JUX1NZTUJPTF9HUEwuIEl0IHdhcyBzaW1wbHkKYW4gb3ZlcnNpZ2h0IHRoYXQgdGhlc2Ug d2VyZSBFWFBPUlRfU1lNQk9MIHByZXZpb3VzbHkuCgo+IEluIGFueSBjYXNlCj4gUmV2aWV3ZWQt Ynk6ICJKw6lyw7RtZSBHbGlzc2UiIDxqZ2xpc3NlQHJlZGhhdC5jb20+CgpUaGFua3MhCl9fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fCkxpbnV4LW52ZGltbSBt YWlsaW5nIGxpc3QKTGludXgtbnZkaW1tQGxpc3RzLjAxLm9yZwpodHRwczovL2xpc3RzLjAxLm9y Zy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LW52ZGltbQo= From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932858AbeCLSRh (ORCPT ); Mon, 12 Mar 2018 14:17:37 -0400 Received: from mail-oi0-f67.google.com ([209.85.218.67]:43182 "EHLO mail-oi0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932829AbeCLSR0 (ORCPT ); Mon, 12 Mar 2018 14:17:26 -0400 X-Google-Smtp-Source: AG47ELsCHn/8PA104eOModbia8XNqvksYjeyswSkTBmFyJrSv73lS9WcoeCqXmpCQ9ACA5F8JS8YSEIfN0X+55wWJbI= MIME-Version: 1.0 In-Reply-To: <20180312141721.GB4214@redhat.com> References: <152066488891.40260.14605734226832760468.stgit@dwillia2-desk3.amr.corp.intel.com> <152066492680.40260.6843692416565308005.stgit@dwillia2-desk3.amr.corp.intel.com> <20180312141721.GB4214@redhat.com> From: Dan Williams Date: Mon, 12 Mar 2018 11:17:25 -0700 Message-ID: Subject: Re: [PATCH v5 07/11] mm, dev_pagemap: introduce CONFIG_DEV_PAGEMAP_OPS To: Jerome Glisse Cc: linux-nvdimm , Michal Hocko , david , Christoph Hellwig , linux-xfs , linux-fsdevel , Jan Kara , Ross Zwisler , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by mail.home.local id w2CIJVDw009903 On Mon, Mar 12, 2018 at 7:17 AM, Jerome Glisse wrote: > On Fri, Mar 09, 2018 at 10:55:26PM -0800, Dan Williams wrote: >> The HMM sub-system extended dev_pagemap to arrange a callback when a >> dev_pagemap managed page is freed. Since a dev_pagemap page is free / >> idle when its reference count is 1 it requires an additional branch to >> check the page-type at put_page() time. Given put_page() is a hot-path >> we do not want to incur that check if HMM is not in use, so a static >> branch is used to avoid that overhead when not necessary. >> >> Now, the FS_DAX implementation wants to reuse this mechanism for >> receiving dev_pagemap ->page_free() callbacks. Rework the HMM-specific >> static-key into a generic mechanism that either HMM or FS_DAX code paths >> can enable. > > Why EXPORT_SYMBOL_GPL and not EXPORT_SYMBOL like it was prior to this > patch ? Not i care that much about that, just wondering. Maybe keep it > EXPORT_SYMBOL() ? HMM has significant integrations and useful hacks within the mm sub-system, I think we should go further than just these symbols and also include devm_memremap_pages() as EXPORT_SYMBOL_GPL. It was simply an oversight that these were EXPORT_SYMBOL previously. > In any case > Reviewed-by: "Jérôme Glisse" Thanks!