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=-9.0 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 98D57C64E7C for ; Wed, 2 Dec 2020 18:38:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 301852173E for ; Wed, 2 Dec 2020 18:38:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730820AbgLBSiP (ORCPT ); Wed, 2 Dec 2020 13:38:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730501AbgLBSiO (ORCPT ); Wed, 2 Dec 2020 13:38:14 -0500 Received: from mail-qv1-xf43.google.com (mail-qv1-xf43.google.com [IPv6:2607:f8b0:4864:20::f43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 69A4FC0613D4 for ; Wed, 2 Dec 2020 10:37:34 -0800 (PST) Received: by mail-qv1-xf43.google.com with SMTP id ek7so1183718qvb.6 for ; Wed, 02 Dec 2020 10:37:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=jCAyA0jCI6f+1wOWuEY4R7HOx3MXmMVjxHY13v0w5DM=; b=cMxqrxGFgOQmnSCaGG7z1BQfaULQzrkMeykxLSnjQugPEWAScf1OgO0ifduABVlr8F 4skrLojzBNF/FQl/4CTpC1F7lGDYF09zuMQsj0BOWrAKniXNVOVcTk+7GIsFbXS47ftg UDze6J/lH+cjOiEDbx30XjfzeHCkXNaG8HKzTppUOOwzKLbYultZPtGZpU9ZM1HHhfcw JBafZOfKMlzz5dXGyQ0wdXn6ZWvjDS4nEL5JcgPUyCPM3aFm0dpmo7nte+x6zpWEW5xU Hy/vP+sPYpxwi38SG5VhMcc+trnnzVBGMlujDd5J0ILWGK4XgKkhjRBrHNNBXuzqSWyX PR/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=jCAyA0jCI6f+1wOWuEY4R7HOx3MXmMVjxHY13v0w5DM=; b=cdCPUCcWxD0uoHhPgOhi+ajY1B5Fquvfr4ADGNnDHpNBX2wqDbQYFY2AH5DOakuqVT xIxSpe4JRiZnlaF5OeK0v5JwfzcNcvL0txMzXpb+rRaKtDBMy8fX4e5mZy/LRdBf+q+F 2XZj1BVWYP/aDEWmef9sKeaq332Vy0Ir4D6Hg5qEJRGZiVRtpKJE5FIX5tkJc/a7EsoC 9Isy9VtZnqs554VASb3upmACL7DIcIs5QKWJbhy74luJ85TQ3hojXO1qxPGNUXRf0LlL uxU8+RPFbcbI41T4o2mA17t3unJ17vCv324g7l5zhIEf31e7iAVrYSEw6SCH2ZaSwHTF D0+A== X-Gm-Message-State: AOAM530+aJ7IUleS1m/hC8J+GAmF98Tf1yKgINkV44FeCHhX0hgsk1Wd qe+E8vKtM4e4L+ICnxIkw+Q= X-Google-Smtp-Source: ABdhPJydMMzDeiYQkc6sbPiXWtNCfX19PTyKXvkVC6Yv8iyVk/TJxaqbAxNE2BbW/skjH0qYP0+Bdg== X-Received: by 2002:a0c:9121:: with SMTP id q30mr3909008qvq.17.1606934253629; Wed, 02 Dec 2020 10:37:33 -0800 (PST) Received: from localhost ([2620:10d:c091:480::1:8dbd]) by smtp.gmail.com with ESMTPSA id y44sm2888335qtb.50.2020.12.02.10.37.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Dec 2020 10:37:32 -0800 (PST) Sender: Tejun Heo Date: Wed, 2 Dec 2020 13:37:05 -0500 From: Tejun Heo To: Fox Chen Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] kernfs: replace the mutex in kernfs_iop_permission with a rwlock Message-ID: References: <20201202145837.48040-1-foxhlchen@gmail.com> <20201202145837.48040-2-foxhlchen@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201202145837.48040-2-foxhlchen@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Dec 02, 2020 at 10:58:36PM +0800, Fox Chen wrote: > diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h > index 89f6a4214a70..545cdb39b34b 100644 > --- a/include/linux/kernfs.h > +++ b/include/linux/kernfs.h > @@ -156,6 +156,7 @@ struct kernfs_node { > unsigned short flags; > umode_t mode; > struct kernfs_iattrs *iattr; > + rwlock_t iattr_rwlock; > }; Also, while this might not look like much, kernfs_node is very size sensitive. There are systems with huge number of these nodes, so I don't think putting a per-node lock like this is a good idea. Either we can use a shared iattr protecting lock or play some cmpxchg games when allocating and setting ->iattr and put the lock there. Thanks. -- tejun