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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 5CBDBC6377D for ; Thu, 22 Jul 2021 17:44:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C6AF61285 for ; Thu, 22 Jul 2021 17:44:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229915AbhGVRD6 (ORCPT ); Thu, 22 Jul 2021 13:03:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:56346 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229514AbhGVRDy (ORCPT ); Thu, 22 Jul 2021 13:03:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id AEB5061001; Thu, 22 Jul 2021 17:44:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626975869; bh=+1VtaWnpu+/vg0Zu7lXitOvQJPQ5sE29/Tcbn/mDaJw=; h=Date:From:To:Subject:References:In-Reply-To:From; b=u9loRPsvhcfjzmctIAYBGzicMdiPmZqpfANrWNV1BIb+tJZ1mV4+NfLphNTnNOjFw 0fYVzaBKoTyQQdm1nepJPpgg1xgGlAEim3ygYRtMdpm4LC47XBlBlKHkpWkurwviqD iWfDT6PVBKnQz5kIaf5V0fuLFxoV9JQl15oyGAMA0VtnzCoBsjsZWVFqoS/dYDERT7 cE0XlVtO7R9hpOf7hNdIddYQsD9t1tsA/djWeL7ANoy0SEnSlbyvBpWhuB/AwiRPjW Zfe5RBXrWFHJ0ngUsedMe0z6+sQS7Q5shV+pn1bs2Vwc+s0N37xXeNfg68L3eb6imB eTNrgs0SpkPUw== Date: Thu, 22 Jul 2021 10:44:28 -0700 From: Jaegeuk Kim To: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [PATCH v2] f2fs: don't sleep while grabing nat_tree_lock Message-ID: References: <20210722014149.525166-1-jaegeuk@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210722014149.525166-1-jaegeuk@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This tries to fix priority inversion in the below condition resulting in long checkpoint delay. f2fs_get_node_info() - nat_tree_lock -> sleep to grab journal_rwsem by contention checkpoint - waiting for nat_tree_lock In order to let checkpoint go, let's release nat_tree_lock, if there's a journal_rwsem contention. Signed-off-by: Jaegeuk Kim --- Change log from v1: - drop rwlock but take retry logic to reduce lock-holding time fs/f2fs/node.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c index 0be9e2d7120e..c60ba4179bb2 100644 --- a/fs/f2fs/node.c +++ b/fs/f2fs/node.c @@ -552,7 +552,7 @@ int f2fs_get_node_info(struct f2fs_sb_info *sbi, nid_t nid, int i; ni->nid = nid; - +retry: /* Check nat cache */ down_read(&nm_i->nat_tree_lock); e = __lookup_nat_cache(nm_i, nid); @@ -564,10 +564,16 @@ int f2fs_get_node_info(struct f2fs_sb_info *sbi, nid_t nid, return 0; } - memset(&ne, 0, sizeof(struct f2fs_nat_entry)); + /* + * Check current segment summary by trying to grab journal_rwsem first. + * This sem is on the critical path on the checkpoint requiring the above + * nat_tree_lock. Therefore, we should retry, if we failed to grab here. + */ + if (!down_read_trylock(&curseg->journal_rwsem)) { + up_read(&nm_i->nat_tree_lock); + goto retry; + } - /* Check current segment summary */ - down_read(&curseg->journal_rwsem); i = f2fs_lookup_journal_in_cursum(journal, NAT_JOURNAL, nid, 0); if (i >= 0) { ne = nat_in_journal(journal, i); -- 2.32.0.432.gabb21c7263-goog