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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 73A42C32774 for ; Tue, 23 Aug 2022 05:33:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240014AbiHWFd2 (ORCPT ); Tue, 23 Aug 2022 01:33:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60942 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238558AbiHWFdZ (ORCPT ); Tue, 23 Aug 2022 01:33:25 -0400 Received: from mail-pf1-x42c.google.com (mail-pf1-x42c.google.com [IPv6:2607:f8b0:4864:20::42c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52DC162CA for ; Mon, 22 Aug 2022 22:33:23 -0700 (PDT) Received: by mail-pf1-x42c.google.com with SMTP id y15so8468380pfr.9 for ; Mon, 22 Aug 2022 22:33:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc; bh=/GFR/eBHEhPX0G8BdA3Wshib8j1DCBk1nG3MDC50vbc=; b=tr24EbXeGwR5nsUyjC8VSTM6dVj8ql9kNWygHPAhDW+87f7YPTy35rl+Pafvt/b7Jv iZlXinH+lwkstOIUzdXEogEElQ8byslQuAbap6AXFiAVBx7t2XnzaILgs91HZ8TwZO0e f78++2T0IAQ1MnIjV9OT9Tack8qFfLwbmDiU+aqWljTNqLo3iCtLmrq2HvkyDYera8qx JIizu5ifVqWezQFiDdmHil0GI595Gv72ss6H2InWKa9wa9oCweU6/wSGSYPfX8u6F0Uq 62HjHHNrkqMN4g72vEXYImkxddyZIGBAGy70yV8qpCYsh/me4b8BSkpts9xj+9t4xZhp 9NMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc; bh=/GFR/eBHEhPX0G8BdA3Wshib8j1DCBk1nG3MDC50vbc=; b=W1/B8hpANttSQEoGRppV0Jo1APVtyZuH9VF/yQ1g8c8tSrKH3zKR5sXjVRLaoeChuY /8h7oq/g23oZZuwsw6z9R5Dshm37mtnbIoTpFCMCf+cnxAjYpwMuhKmxvamrq5P1RkSb 9q3+aAE1rTHCLMoK8pDMdyZbD/rl1d4btHxJeGlu136WrL7nyT+zRMaPwA1GVONEs5Mo rrBb+dUuRhZvKATxZPiA4FVHeRWNkmuZfofZWemQLcWTvZBfp370wEL8fwzlJjzbb6aJ ke9A+z2t2DAYZ1Pt5DoaVrvWGksm3VHCdGR/w5TIiZGXUs4hwVL2qR6ZTZLEQO7bF2Lw dDxA== X-Gm-Message-State: ACgBeo101ybH1BmJXFuR60yRDjjfzh4mZKiHZ1blwP29f0BgMuXffqD3 unp0qCVhQlt8Gx1bUR/VZm4H/Q== X-Google-Smtp-Source: AA6agR5ZDfL1Q7pmClsrDWZa1njQsLMpZdLUz7tKlcKdif0pifg20UDYa37a3lusGrLtIt0JUm8DDA== X-Received: by 2002:a63:8b44:0:b0:41c:df4c:7275 with SMTP id j65-20020a638b44000000b0041cdf4c7275mr19999090pge.434.1661232802793; Mon, 22 Aug 2022 22:33:22 -0700 (PDT) Received: from [10.4.208.12] ([139.177.225.228]) by smtp.gmail.com with ESMTPSA id n4-20020a170903110400b001714e7608fdsm9430886plh.256.2022.08.22.22.33.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 Aug 2022 22:33:21 -0700 (PDT) Message-ID: <04b8cfda-4017-a7dd-65e3-b6746d1898e6@bytedance.com> Date: Tue, 23 Aug 2022 13:33:14 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.1.2 Subject: Re: [PATCH 5/7] kernfs: Make kernfs_drain() skip draining more aggressively Content-Language: en-US To: Tejun Heo , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Johannes Weiner , Imran Khan , kernel-team@fb.com References: <20220820000550.367085-1-tj@kernel.org> <20220820000550.367085-6-tj@kernel.org> From: Chengming Zhou In-Reply-To: <20220820000550.367085-6-tj@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/8/20 08:05, Tejun Heo wrote: > 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)) Should be !kernfs_should_drain_open_files(kn)? I see that diff is put in patch 6/7. Thanks. > + 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