From patchwork Fri Dec 21 19:38:04 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dan Williams X-Patchwork-Id: 10741001 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 A98D31399 for ; Fri, 21 Dec 2018 19:50:42 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 86DE8289D6 for ; Fri, 21 Dec 2018 19:50:42 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 788DC289D5; Fri, 21 Dec 2018 19:50:42 +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=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 09C7B289DD for ; Fri, 21 Dec 2018 19:50:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390046AbeLUTuk (ORCPT ); Fri, 21 Dec 2018 14:50:40 -0500 Received: from mga06.intel.com ([134.134.136.31]:64975 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389508AbeLUTuk (ORCPT ); Fri, 21 Dec 2018 14:50:40 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Dec 2018 11:50:40 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,382,1539673200"; d="scan'208";a="102535180" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.16]) by orsmga006.jf.intel.com with ESMTP; 21 Dec 2018 11:50:40 -0800 Subject: [PATCH] dax: Use non-exclusive wait in wait_entry_unlocked() From: Dan Williams To: linux-fsdevel@vger.kernel.org Cc: Jan Kara , Matthew Wilcox , Linus Torvalds , linux-nvdimm@lists.01.org Date: Fri, 21 Dec 2018 11:38:04 -0800 Message-ID: <154542108460.3682905.4453912339454331429.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.18-2-gc94f MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP get_unlocked_entry() uses an exclusive wait because it is guaranteed to eventually obtain the lock and follow on with an unlock+wakeup cycle. The wait_entry_unlocked() path does not have the same guarantee. Rather than open-code an extra wakeup, just switch to a non-exclusive wait. Cc: Jan Kara Cc: Matthew Wilcox Reported-by: Linus Torvalds Signed-off-by: Dan Williams Reviewed-by: Jan Kara --- fs/dax.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 48132eca3761..042d3b31b413 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -246,18 +246,16 @@ static void wait_entry_unlocked(struct xa_state *xas, void *entry) ewait.wait.func = wake_exceptional_entry_func; wq = dax_entry_waitqueue(xas, entry, &ewait.key); - prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); + /* + * Unlike get_unlocked_entry() there is no guarantee that this + * path ever successfully retrieves an unlocked entry before an + * inode dies. Perform a non-exclusive wait in case this path + * never successfully performs its own wake up. + */ + prepare_to_wait(wq, &ewait.wait, TASK_UNINTERRUPTIBLE); xas_unlock_irq(xas); schedule(); finish_wait(wq, &ewait.wait); - - /* - * Entry lock waits are exclusive. Wake up the next waiter since - * we aren't sure we will acquire the entry lock and thus wake - * the next waiter up on unlock. - */ - if (waitqueue_active(wq)) - __wake_up(wq, TASK_NORMAL, 1, &ewait.key); } static void put_unlocked_entry(struct xa_state *xas, void *entry)