From patchwork Sun Oct 7 05:59:56 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10629365 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0B35B14D6 for ; Sun, 7 Oct 2018 06:11:47 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EA220290C6 for ; Sun, 7 Oct 2018 06:11:46 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DC18329129; Sun, 7 Oct 2018 06:11:46 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 83E2D290C6 for ; Sun, 7 Oct 2018 06:11:46 +0000 (UTC) Received: from [127.0.0.1] (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 5AE4221A07A82; Sat, 6 Oct 2018 23:11:46 -0700 (PDT) X-Original-To: linux-nvdimm@lists.01.org Delivered-To: linux-nvdimm@lists.01.org Received-SPF: Pass (sender SPF authorized) identity=mailfrom; client-ip=192.55.52.136; helo=mga12.intel.com; envelope-from=dan.j.williams@intel.com; receiver=linux-nvdimm@lists.01.org Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 2993721131DB1 for ; Sat, 6 Oct 2018 23:11:45 -0700 (PDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Oct 2018 23:11:44 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.54,351,1534834800"; d="scan'208";a="269139142" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.16]) by fmsmga005.fm.intel.com with ESMTP; 06 Oct 2018 23:11:44 -0700 Subject: [PATCH v2] filesystem-dax: Fix dax_layout_busy_page() livelock From: Dan Williams To: linux-fsdevel@vger.kernel.org Date: Sat, 06 Oct 2018 22:59:56 -0700 Message-ID: <153889193718.3143179.3432479794012686784.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.18-2-gc94f MIME-Version: 1.0 X-BeenThere: linux-nvdimm@lists.01.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Linux-nvdimm developer list." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jan Kara , linux-nvdimm@lists.01.org, linux-kernel@vger.kernel.org, Matthew Wilcox , stable@vger.kernel.org, Ross Zwisler Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" X-Virus-Scanned: ClamAV using ClamSMTP In the presence of multi-order entries the typical pagevec_lookup_entries() pattern may loop forever: while (index < end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { ... for (i = 0; i < pagevec_count(&pvec); i++) { index = indices[i]; ... } index++; /* BUG */ } The loop updates 'index' for each index found and then increments to the next possible page to continue the lookup. However, if the last entry in the pagevec is multi-order then the next possible page index is more than 1 page away. Fix this locally for the filesystem-dax case by checking for dax-multi-order entries. Going forward new users of multi-order entries need to be similarly careful, or we need a generic way to report the page increment in the radix iterator. Fixes: 5fac7408d828 ("mm, fs, dax: handle layout changes to pinned dax...") Cc: Cc: Jan Kara Cc: Ross Zwisler Cc: Matthew Wilcox Signed-off-by: Dan Williams Reviewed-by: Jan Kara --- Changes in v2: * Only update nr_pages if the last entry in the pagevec is multi-order. fs/dax.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 4becbf168b7f..0fb270f0a0ef 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -666,6 +666,8 @@ struct page *dax_layout_busy_page(struct address_space *mapping) while (index < end && pagevec_lookup_entries(&pvec, mapping, index, min(end - index, (pgoff_t)PAGEVEC_SIZE), indices)) { + pgoff_t nr_pages = 1; + for (i = 0; i < pagevec_count(&pvec); i++) { struct page *pvec_ent = pvec.pages[i]; void *entry; @@ -680,8 +682,15 @@ struct page *dax_layout_busy_page(struct address_space *mapping) xa_lock_irq(&mapping->i_pages); entry = get_unlocked_mapping_entry(mapping, index, NULL); - if (entry) + if (entry) { page = dax_busy_page(entry); + /* + * Account for multi-order entries at + * the end of the pagevec. + */ + if (i + 1 >= pagevec_count(&pvec)) + nr_pages = 1UL << dax_radix_order(entry); + } put_unlocked_mapping_entry(mapping, index, entry); xa_unlock_irq(&mapping->i_pages); if (page) @@ -696,7 +705,7 @@ struct page *dax_layout_busy_page(struct address_space *mapping) */ pagevec_remove_exceptionals(&pvec); pagevec_release(&pvec); - index++; + index += nr_pages; if (page) break;