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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 62CA7C41604 for ; Wed, 7 Oct 2020 08:25:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9699E212CC for ; Wed, 7 Oct 2020 08:25:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9699E212CC Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 898876B005C; Wed, 7 Oct 2020 04:25:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 849608E0001; Wed, 7 Oct 2020 04:25:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7378A6B0068; Wed, 7 Oct 2020 04:25:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0247.hostedemail.com [216.40.44.247]) by kanga.kvack.org (Postfix) with ESMTP id 44D006B005C for ; Wed, 7 Oct 2020 04:25:24 -0400 (EDT) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C20E48249980 for ; Wed, 7 Oct 2020 08:25:23 +0000 (UTC) X-FDA: 77344444926.15.mass84_060f70a271cd Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin15.hostedemail.com (Postfix) with ESMTP id A16A91814B0C1 for ; Wed, 7 Oct 2020 08:25:23 +0000 (UTC) X-HE-Tag: mass84_060f70a271cd X-Filterd-Recvd-Size: 4805 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf02.hostedemail.com (Postfix) with ESMTP for ; Wed, 7 Oct 2020 08:25:23 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 96FFBABD1; Wed, 7 Oct 2020 08:25:21 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E96721E1305; Wed, 7 Oct 2020 10:25:17 +0200 (CEST) Date: Wed, 7 Oct 2020 10:25:17 +0200 From: Jan Kara To: Ralph Campbell Cc: linux-mm@kvack.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, Dan Williams , Matthew Wilcox , Jan Kara , Alexander Viro , Theodore Ts'o , Christoph Hellwig , Andreas Dilger , "Darrick J. Wong" , Andrew Morton Subject: Re: [PATCH] ext4/xfs: add page refcount helper Message-ID: <20201007082517.GC6984@quack2.suse.cz> References: <20201006230930.3908-1-rcampbell@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201006230930.3908-1-rcampbell@nvidia.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue 06-10-20 16:09:30, Ralph Campbell wrote: > There are several places where ZONE_DEVICE struct pages assume a reference > count == 1 means the page is idle and free. Instead of open coding this, > add a helper function to hide this detail. > > Signed-off-by: Ralph Campbell > Reviewed-by: Christoph Hellwig Looks as sane direction but if we are going to abstract checks when ZONE_DEVICE page is idle, we should also update e.g. mm/swap.c:put_devmap_managed_page() or mm/gup.c:__unpin_devmap_managed_user_page() (there may be more places like this but I found at least these two...). Maybe Dan has more thoughts about this. Honza > diff --git a/fs/dax.c b/fs/dax.c > index 5b47834f2e1b..85c63f735909 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -358,7 +358,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping, > for_each_mapped_pfn(entry, pfn) { > struct page *page = pfn_to_page(pfn); > > - WARN_ON_ONCE(trunc && page_ref_count(page) > 1); > + WARN_ON_ONCE(trunc && !dax_layout_is_idle_page(page)); > WARN_ON_ONCE(page->mapping && page->mapping != mapping); > page->mapping = NULL; > page->index = 0; > @@ -372,7 +372,7 @@ static struct page *dax_busy_page(void *entry) > for_each_mapped_pfn(entry, pfn) { > struct page *page = pfn_to_page(pfn); > > - if (page_ref_count(page) > 1) > + if (!dax_layout_is_idle_page(page)) > return page; > } > return NULL; > diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c > index 771ed8b1fadb..132620cbfa13 100644 > --- a/fs/ext4/inode.c > +++ b/fs/ext4/inode.c > @@ -3937,10 +3937,7 @@ int ext4_break_layouts(struct inode *inode) > if (!page) > return 0; > > - error = ___wait_var_event(&page->_refcount, > - atomic_read(&page->_refcount) == 1, > - TASK_INTERRUPTIBLE, 0, 0, > - ext4_wait_dax_page(ei)); > + error = dax_wait_page(ei, page, ext4_wait_dax_page); > } while (error == 0); > > return error; > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index 3d1b95124744..a5304aaeaa3a 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -749,9 +749,7 @@ xfs_break_dax_layouts( > return 0; > > *retry = true; > - return ___wait_var_event(&page->_refcount, > - atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE, > - 0, 0, xfs_wait_dax_page(inode)); > + return dax_wait_page(inode, page, xfs_wait_dax_page); > } > > int > diff --git a/include/linux/dax.h b/include/linux/dax.h > index b52f084aa643..8909a91cd381 100644 > --- a/include/linux/dax.h > +++ b/include/linux/dax.h > @@ -243,6 +243,16 @@ static inline bool dax_mapping(struct address_space *mapping) > return mapping->host && IS_DAX(mapping->host); > } > > +static inline bool dax_layout_is_idle_page(struct page *page) > +{ > + return page_ref_count(page) == 1; > +} > + > +#define dax_wait_page(_inode, _page, _wait_cb) \ > + ___wait_var_event(&(_page)->_refcount, \ > + dax_layout_is_idle_page(_page), \ > + TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode)) > + > #ifdef CONFIG_DEV_DAX_HMEM_DEVICES > void hmem_register_device(int target_nid, struct resource *r); > #else > -- > 2.20.1 > -- Jan Kara SUSE Labs, CR