From patchwork Sat Aug 20 00:05:49 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Tejun Heo X-Patchwork-Id: 12949398 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 06F3EC3814E for ; Sat, 20 Aug 2022 00:06:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244558AbiHTAGR (ORCPT ); Fri, 19 Aug 2022 20:06:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59136 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244401AbiHTAGN (ORCPT ); Fri, 19 Aug 2022 20:06:13 -0400 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1AE47C59E4; Fri, 19 Aug 2022 17:06:12 -0700 (PDT) Received: by mail-pl1-x62b.google.com with SMTP id 20so5343736plo.10; Fri, 19 Aug 2022 17:06:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:from:to:cc; bh=mALUVzvQkNStgXaHgA3odIsd31YxLLGk1d2u95EoEbw=; b=oVeJjDc3RH46Mfe5B8tkD6PdFxEdVoazg8nbQW8oMsw3JPk3gclva8LRuwooFi+Yhh UfACsm70DPl4YknurmVAfkFyLXAamAb97UiskrCdJtVzSTyr8X2urqsw9ATZ2dvKEKFF 7Fz69+byXmQoQrPx2UWpf3cumRScIwLF5Vtwa9JKlCHlU+JBAO/ZkDjjvNoYGFDiQtEv hxs4xUDLt6wXUlvj/SN2j2NNZwMxBEh15P4WTc5cwcQHkQlX8U+FJC3zUiV1YwZLLQwK aUiTaqwJis86CwvPFaBCY7LfO0Ntl1V1B9r7AJOtEn56f/Wj9Isj3Vp7eOJYUf/BtIJQ KBfw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:sender:x-gm-message-state:from :to:cc; bh=mALUVzvQkNStgXaHgA3odIsd31YxLLGk1d2u95EoEbw=; b=QePyw8PQZ5o159b1GG5rh6yiB6nWkzOmqKHOXE1o9HTjlgq1maO/kC3ba5HNzqmq6k Ii7W3hm12hhEI6v28LqFIyzdXEXJjsnH6dM0+CKfAXmbawvZwEWXH0RJAim66kio26gP kN9m4gEtjfjPQSfB/rI20X2Hw1OrV5g7cFD9xNNX84i9dGwM95lnYyJtDzYFcU/C7Wh4 nmpQt5Ig+s7Y/oOyk8mrxZaks9x2tnLiECY4Y3ZHJtgfFPt2yb1hNs5x1YIVwECGU698 x7AJPYCxeBnUaSq2Ak0+z6XLDuQ/rbE9swF4X2ZILkNJGw61vRF/RWNl06hh296YpExF LUXg== X-Gm-Message-State: ACgBeo08t+ZcFvES3PUjJ3rPuZQDD0KaPOwiKuRs6jSdhQBq9mqsBhRO /LmymIAHjUN7dwsfihva+7MqcqZy4gI= X-Google-Smtp-Source: AA6agR5CM7J59rSZzXsxpmaVSmGNSqOdihNEvMdBamjMVcEi3uhG6gbUPPwADBu38U+aO5iWNfMhdw== X-Received: by 2002:a17:902:c411:b0:170:91ff:884b with SMTP id k17-20020a170902c41100b0017091ff884bmr9656022plk.58.1660953971444; Fri, 19 Aug 2022 17:06:11 -0700 (PDT) Received: from localhost ([2620:10d:c090:400::5:a2f5]) by smtp.gmail.com with ESMTPSA id f7-20020a170902684700b0016d93c84049sm3702023pln.54.2022.08.19.17.06.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Aug 2022 17:06:11 -0700 (PDT) Sender: Tejun Heo From: Tejun Heo To: Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Chengming Zhou , Johannes Weiner , Imran Khan , kernel-team@fb.com, Tejun Heo Subject: [PATCH 5/7] kernfs: Make kernfs_drain() skip draining more aggressively Date: Fri, 19 Aug 2022 14:05:49 -1000 Message-Id: <20220820000550.367085-6-tj@kernel.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220820000550.367085-1-tj@kernel.org> References: <20220820000550.367085-1-tj@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org kernfs_drain() is updated to handle whether draining is necessary or not rather than its caller. __kernfs_remove() now always calls kernfs_drain() instead of filtering based on KERNFS_ACTIVATED. kernfs_drain() now tests kn->active and kernfs_should_drain_open_files() to determine whether draining is necessary at all. If not, it returns %false without doing anything. Otherwise, it unlocks kernfs_rwsem and drains as before and returns %true. The return value isn't used yet. Using the precise conditions allows skipping more aggressively. This isn't a meaningful optimization on its own but will enable future stand-alone kernfs_deactivate() implementation. While at it, make minor comment updates. Signed-off-by: Tejun Heo --- fs/kernfs/dir.c | 34 ++++++++++++++++++++-------------- 1 file changed, 20 insertions(+), 14 deletions(-) diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 8ae44db920d4..f857731598cd 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -460,10 +460,14 @@ void kernfs_put_active(struct kernfs_node *kn) * @kn: kernfs_node to drain * * Drain existing usages and nuke all existing mmaps of @kn. Mutiple - * removers may invoke this function concurrently on @kn and all will + * callers may invoke this function concurrently on @kn and all will * return after draining is complete. + * + * RETURNS: + * %false if nothing needed to be drained; otherwise, %true. On %true return, + * kernfs_rwsem has been released and re-acquired. */ -static void kernfs_drain(struct kernfs_node *kn) +static bool kernfs_drain(struct kernfs_node *kn) __releases(&kernfs_root(kn)->kernfs_rwsem) __acquires(&kernfs_root(kn)->kernfs_rwsem) { @@ -472,6 +476,16 @@ static void kernfs_drain(struct kernfs_node *kn) lockdep_assert_held_write(&root->kernfs_rwsem); WARN_ON_ONCE(kernfs_active(kn)); + /* + * Skip draining if already fully drained. This avoids draining and its + * lockdep annotations for nodes which have never been activated + * allowing embedding kernfs_remove() in create error paths without + * worrying about draining. + */ + if (atomic_read(&kn->active) == KN_DEACTIVATED_BIAS && + kernfs_should_drain_open_files(kn)) + return false; + up_write(&root->kernfs_rwsem); if (kernfs_lockdep(kn)) { @@ -480,7 +494,6 @@ static void kernfs_drain(struct kernfs_node *kn) lock_contended(&kn->dep_map, _RET_IP_); } - /* but everyone should wait for draining */ wait_event(root->deactivate_waitq, atomic_read(&kn->active) == KN_DEACTIVATED_BIAS); @@ -493,6 +506,8 @@ static void kernfs_drain(struct kernfs_node *kn) kernfs_drain_open_files(kn); down_write(&root->kernfs_rwsem); + + return true; } /** @@ -1370,23 +1385,14 @@ static void __kernfs_remove(struct kernfs_node *kn) pos = kernfs_leftmost_descendant(kn); /* - * kernfs_drain() drops kernfs_rwsem temporarily and @pos's + * kernfs_drain() may drop kernfs_rwsem temporarily and @pos's * base ref could have been put by someone else by the time * the function returns. Make sure it doesn't go away * underneath us. */ kernfs_get(pos); - /* - * Drain iff @kn was activated. This avoids draining and - * its lockdep annotations for nodes which have never been - * activated and allows embedding kernfs_remove() in create - * error paths without worrying about draining. - */ - if (kn->flags & KERNFS_ACTIVATED) - kernfs_drain(pos); - else - WARN_ON_ONCE(atomic_read(&kn->active) != KN_DEACTIVATED_BIAS); + kernfs_drain(pos); /* * kernfs_unlink_sibling() succeeds once per node. Use it