From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5B667C43215 for ; Thu, 14 Nov 2019 07:25:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 24B26206E6 for ; Thu, 14 Nov 2019 07:25:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=intel-com.20150623.gappssmtp.com header.i=@intel-com.20150623.gappssmtp.com header.b="ka9TFfKo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 24B26206E6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C53EE6B0006; Thu, 14 Nov 2019 02:25:37 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C2A166B0008; Thu, 14 Nov 2019 02:25:37 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B66946B000A; Thu, 14 Nov 2019 02:25:37 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0121.hostedemail.com [216.40.44.121]) by kanga.kvack.org (Postfix) with ESMTP id 988116B0006 for ; Thu, 14 Nov 2019 02:25:37 -0500 (EST) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 3AADC8249980 for ; Thu, 14 Nov 2019 07:25:37 +0000 (UTC) X-FDA: 76154047914.04.bed78_30d7a166fc026 X-HE-Tag: bed78_30d7a166fc026 X-Filterd-Recvd-Size: 5011 Received: from mail-oi1-f196.google.com (mail-oi1-f196.google.com [209.85.167.196]) by imf36.hostedemail.com (Postfix) with ESMTP for ; Thu, 14 Nov 2019 07:25:35 +0000 (UTC) Received: by mail-oi1-f196.google.com with SMTP id l202so4418607oig.1 for ; Wed, 13 Nov 2019 23:25:35 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=f5d5/bpHoXBtRihRqTs8DB3/xqD8D283lsRAFtLbrfY=; b=ka9TFfKoK65lEg8yCbO74ziezgRtQdVgpXv0yhH69HHcnCDQeoZMEx0zXoBS7PR5CR HUSM9ldvvNqYmMcaebJWojK6kxK8YredJDVlobIurEivs8HOFwov2jkpRQva3FuViGRf ZaqsOLOTzq/jVjwP4ypul0EYWEaO7bvk7hbPzNM96uv6Cgr5HBNYLPmiYoYyOFHvE9hD mXVwpyQKlHtexK/PvqnnO2dznfTmoig1liLGmqjelsl+RrlPIQi/2x1HOJVbWTe4SI/d 3v/ItiNlUzTdLdfu/x+OUPTS84IMvoks4EpIT9ybpTurledVYXiFfLBuX7ocfw5Mez8k y+4Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=f5d5/bpHoXBtRihRqTs8DB3/xqD8D283lsRAFtLbrfY=; b=mpPLD5i4KlUHqpPTe9pCuV3nQS0IbS8fk5pcrndnOYX7QwOL5z8r7SZ5u0jWp4Yi2g /PddGUgQN5nZgVR0FvswDK5D8BCWIAceE7OyvYUycQfXqg0A4U+8EyEfDdbcz0mS8F+y U/iNhYm5rJnHTsLrtWE4sxoOPKirBmP3AOR1NaT3srCQIhW4l6iDdjgb+I4V0GSEOGOm M7LzGyPkL0QXEEdPWmYvx8sGMblV+tmIsj++M7IeL+Wv9K+OOwGUmV+vmj+LnL69+AW4 Fwa1MbNmk64kylivLsRb56wsHWh/ApPf3lFzv/SWDD+O/V+LpLfJVV6jvxReuBxtKbiZ ihAw== X-Gm-Message-State: APjAAAXY9FChBBloCOXOcbQS72JBwAoH7D6UaZLUOPFrkFInp3yLoVrM 8AeghNimXdZSA4I+wza93f5eS77VO7Lnreoi5i6dvA== X-Google-Smtp-Source: APXvYqyw6GUqimMOF1WKHvSfkunTVJ/My/V0dioePYkRQ/odDMDx25P6oQDKSOWhF5aoTpM0cuCpZKOnaci5mnKBdMI= X-Received: by 2002:a05:6808:1da:: with SMTP id x26mr720739oic.149.1573716334479; Wed, 13 Nov 2019 23:25:34 -0800 (PST) MIME-Version: 1.0 References: <157368992671.2974225.13512647385398246617.stgit@dwillia2-desk3.amr.corp.intel.com> <20191114071903.GA26307@lst.de> In-Reply-To: <20191114071903.GA26307@lst.de> From: Dan Williams Date: Wed, 13 Nov 2019 23:25:23 -0800 Message-ID: Subject: Re: [PATCH] mm: Cleanup __put_devmap_managed_page() vs ->page_free() To: Christoph Hellwig Cc: John Hubbard , Jan Kara , Ira Weiny , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , linux-nvdimm , Linux Kernel Mailing List , Linux MM Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Nov 13, 2019 at 11:19 PM Christoph Hellwig wrote: > > On Wed, Nov 13, 2019 at 04:07:22PM -0800, Dan Williams wrote: > > static int devmap_managed_enable_get(struct dev_pagemap *pgmap) > > { > > - if (!pgmap->ops || !pgmap->ops->page_free) { > > + if (!pgmap->ops || (pgmap->type == MEMORY_DEVICE_PRIVATE > > + && !pgmap->ops->page_free)) { > > I don't think this check is correct. You only want the the ops null check > or MEMORY_DEVICE_PRIVATE as well now, i.e.: > > if (pgmap->type == MEMORY_DEVICE_PRIVATE && > (!pgmap->ops || !pgmap->ops->page_free)) { > > > @@ -476,10 +471,17 @@ void __put_devmap_managed_page(struct page *page) > > * handled differently or not done at all, so there is no need > > * to clear page->mapping. > > */ > > - if (is_device_private_page(page)) > > - page->mapping = NULL; > > + if (is_device_private_page(page)) { > > + /* Clear Active bit in case of parallel mark_page_accessed */ > > This adds a > 80 char line. But that whole flow of the function seems > rather odd now. > > Why can't we do: > > if (count == 0) { > __put_page(page); > } else if (is_device_private_page(page)) { > __ClearPageActive(page); > __ClearPageWaiters(page); > > mem_cgroup_uncharge(page); > page->mapping = NULL; > page->pgmap->ops->page_free(page); > } else { > wake_up_var(&page->_refcount); > } > All the above looks good to me will spin a v2. > (except for the fact that I don't get the point of calling __put_page > on a refcount of zero, but that is separate from this patch). That looked odd to me as well until I recalled that we did that to simplify the pgmap reference counting. 71389703839e mm, zone_device: Replace {get, put}_zone_device_page() with a single reference to fix pmem crash I'll add a comment in v2.