From patchwork Thu Jun 2 18:18:11 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Logan Gunthorpe X-Patchwork-Id: 12868057 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D4C4DC43334 for ; Thu, 2 Jun 2022 18:18:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237268AbiFBSSr (ORCPT ); Thu, 2 Jun 2022 14:18:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237945AbiFBSSg (ORCPT ); Thu, 2 Jun 2022 14:18:36 -0400 Received: from ale.deltatee.com (ale.deltatee.com [204.191.154.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA0904E39D; Thu, 2 Jun 2022 11:18:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=deltatee.com; s=20200525; h=Subject:MIME-Version:References:In-Reply-To: Message-Id:Date:Cc:To:From:content-disposition; bh=KPxyHl5McdIBsrZVYzmedsuwOe9Hs+sIzKMYT+CRgdg=; b=LrSxondlmjxzZxumaLp+VeRQmL +w29AInQ3Q5NOcs2iyjAo8P1tOCCAdrn2QglNlg7cBAfz8mUSwyE59rJwCEaj2qqdW/IpSxBdkJ69 qBtVxXDt8alIh8LRXVDde0zJPaoajE5Q6+N2M966Oy7YZQMDJO1vOlbmGusYi7ic1L7hXqJHqh3+V TEcNUmWG3wNoO+32fdszC037WEzcF7Okw5gvPh1W70Z6lzq9ybdMJ/wyQOEcqOYxD5o4rLyLKozSk fLfK5ywNlZP4kFUNTvY8kBU3ckFYJkspm8bZlcLUF+L08srAfP2Nh0I9EmHuSaP3moj7EiUtMCTZw /w7aY6dQ==; Received: from cgy1-donard.priv.deltatee.com ([172.16.1.31]) by ale.deltatee.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1nwpOo-00EPmV-R8; Thu, 02 Jun 2022 12:18:23 -0600 Received: from gunthorp by cgy1-donard.priv.deltatee.com with local (Exim 4.94.2) (envelope-from ) id 1nwpOm-000DDP-52; Thu, 02 Jun 2022 12:18:20 -0600 From: Logan Gunthorpe To: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, Song Liu Cc: Christoph Hellwig , Donald Buczek , Guoqing Jiang , Xiao Ni , Stephen Bates , Martin Oliveira , David Sloan , Logan Gunthorpe Date: Thu, 2 Jun 2022 12:18:11 -0600 Message-Id: <20220602181818.50729-6-logang@deltatee.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220602181818.50729-1-logang@deltatee.com> References: <20220602181818.50729-1-logang@deltatee.com> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 172.16.1.31 X-SA-Exim-Rcpt-To: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, song@kernel.org, hch@infradead.org, buczek@molgen.mpg.de, guoqing.jiang@linux.dev, xni@redhat.com, sbates@raithlin.com, Martin.Oliveira@eideticom.com, David.Sloan@eideticom.com, logang@deltatee.com X-SA-Exim-Mail-From: gunthorp@deltatee.com Subject: [PATCH v3 05/11] md/raid5-cache: Drop RCU usage of conf->log X-SA-Exim-Version: 4.2.1 (built Sat, 13 Feb 2021 17:57:42 +0000) X-SA-Exim-Scanned: Yes (on ale.deltatee.com) Precedence: bulk List-ID: X-Mailing-List: linux-raid@vger.kernel.org The only place that uses RCU to access conf->log is in r5l_log_disk_error(). This function is mostly used in the IO path and once with mddev_lock() held in raid5_change_consistency_policy(). It is known that the IO will be suspended before the log is freed and r5l_log_exit() is called with the mddev_lock() held. This should mean that conf->log can not be freed while the function is being called, so the RCU protection is not necessary. Drop the rcu_read_lock() as well as the synchronize_rcu() and rcu_assign_pointer() usage. Signed-off-by: Logan Gunthorpe Reviewed-by: Christoph Hellwig --- drivers/md/raid5-cache.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-) diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 69b95005abca..48020d36b334 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -1590,18 +1590,13 @@ void r5l_quiesce(struct r5l_log *log, int quiesce) bool r5l_log_disk_error(struct r5conf *conf) { - struct r5l_log *log; - bool ret; - /* don't allow write if journal disk is missing */ - rcu_read_lock(); - log = rcu_dereference(conf->log); + struct r5l_log *log = conf->log; + /* don't allow write if journal disk is missing */ if (!log) - ret = test_bit(MD_HAS_JOURNAL, &conf->mddev->flags); + return test_bit(MD_HAS_JOURNAL, &conf->mddev->flags); else - ret = test_bit(Faulty, &log->rdev->flags); - rcu_read_unlock(); - return ret; + return test_bit(Faulty, &log->rdev->flags); } #define R5L_RECOVERY_PAGE_POOL_SIZE 256 @@ -3148,7 +3143,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev) spin_lock_init(&log->stripe_in_journal_lock); atomic_set(&log->stripe_in_journal_count, 0); - rcu_assign_pointer(conf->log, log); + conf->log = log; set_bit(MD_HAS_JOURNAL, &conf->mddev->flags); return 0; @@ -3173,7 +3168,6 @@ void r5l_exit_log(struct r5conf *conf) lockdep_assert_held(&conf->mddev->reconfig_mutex); conf->log = NULL; - synchronize_rcu(); /* Ensure disable_writeback_work wakes up and exits */ wake_up(&conf->mddev->sb_wait);