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=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 AF91CC48BD1 for ; Fri, 11 Jun 2021 13:14:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8BBCB613E3 for ; Fri, 11 Jun 2021 13:14:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231599AbhFKNQs (ORCPT ); Fri, 11 Jun 2021 09:16:48 -0400 Received: from mail-ua1-f42.google.com ([209.85.222.42]:34635 "EHLO mail-ua1-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229633AbhFKNQp (ORCPT ); Fri, 11 Jun 2021 09:16:45 -0400 Received: by mail-ua1-f42.google.com with SMTP id c17so2558923uao.1 for ; Fri, 11 Jun 2021 06:14:48 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=EaDxm7CAMccH6BxkH3jMQSzq1sz+JsTOHJ81BcDQxlc=; b=Ex2De4dHAN5GsZSCNxo84B8s/T/KbAuuiZl/QmTRrOZ5HiOuqZh7rYh4QgJVvpYv8B fxNg5SPcXBuIk3m7aqDwhkoHklDHFoT7qrk2VlpMKDu05oeWd3ppy767v/LYMxqFwqjE aLOK5ZY2PyQCHetjeEqvNAnQU60n064ubIDjI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=EaDxm7CAMccH6BxkH3jMQSzq1sz+JsTOHJ81BcDQxlc=; b=Tpb6CtBZUGpwhHhWam1gxH6kbLOLCoKuLQVTn00q6dcRnuvHDL/6mEtvQDozRXwyCq 1+RK008MKdUc8XyLQWSUcijUOI/KLnrFsUzSC5yNIWnjr86iCr7GWrfTBoXN4fpzmQUv lrVQnXUNHQLJFxADzZA6u5TfnvynnujY5/BfqO+E9b7ea3KkqGe4ZQ6pIngiQRolWKF/ WL7T79KCQrhvLtdXmbiOPnDeXYndcV1RoGiZiVPj8+VO+GFwVAtgHHyMJ2qfGz6zKa/r alGm+4bvbJZuOHXXFFL4ApDrrorSSp+YsBVGermp/TnUbZMyiTIKZt4onZa4xUY1upX3 ZA3w== X-Gm-Message-State: AOAM530TfkvosMB1115J+SbEFGDwb5bghkdBChTBIOKB+fkiWupaYFey TQB0+RYerY/xacRoihOplEGXNkaTkUZx/QdMYdub+Q== X-Google-Smtp-Source: ABdhPJx44Ziz7vPRZ46bsBmuGBMqTKcmVOpww5OiQk+u1PD4sFDnONguBzgZ3BY8hkisnZD5KFTvHUQILKdDYVrB5YM= X-Received: by 2002:ab0:2690:: with SMTP id t16mr2923322uao.9.1623417227768; Fri, 11 Jun 2021 06:13:47 -0700 (PDT) MIME-Version: 1.0 References: <162322846765.361452.17051755721944717990.stgit@web.messagingengine.com> <162322872534.361452.17619177755627322271.stgit@web.messagingengine.com> In-Reply-To: <162322872534.361452.17619177755627322271.stgit@web.messagingengine.com> From: Miklos Szeredi Date: Fri, 11 Jun 2021 15:13:37 +0200 Message-ID: Subject: Re: [PATCH v6 6/7] kernfs: add kernfs_need_inode_refresh() To: Ian Kent Cc: Greg Kroah-Hartman , Tejun Heo , Eric Sandeen , Fox Chen , Brice Goglin , Al Viro , Rick Lindsley , David Howells , Marcelo Tosatti , "Eric W. Biederman" , Carlos Maiolino , linux-fsdevel , Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, 9 Jun 2021 at 10:52, Ian Kent wrote: > > Now the kernfs_rwsem read lock is held for kernfs_refresh_inode() and > the i_lock taken to protect inode updates there can be some contention > introduced when .permission() is called with concurrent path walks in > progress. > > Since .permission() is called frequently during path walks it's worth > checking if the update is actually needed before taking the lock and > performing the update. > > Signed-off-by: Ian Kent Reviewed-by: Miklos Szeredi