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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 F1A71C4361B for ; Tue, 15 Dec 2020 16:42:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8983223D6 for ; Tue, 15 Dec 2020 16:42:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728676AbgLOQmO (ORCPT ); Tue, 15 Dec 2020 11:42:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34644 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726278AbgLOQmO (ORCPT ); Tue, 15 Dec 2020 11:42:14 -0500 Received: from mail-lf1-x141.google.com (mail-lf1-x141.google.com [IPv6:2a00:1450:4864:20::141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F012BC06179C; Tue, 15 Dec 2020 08:41:33 -0800 (PST) Received: by mail-lf1-x141.google.com with SMTP id s26so6351201lfc.8; Tue, 15 Dec 2020 08:41:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=piepAd/SOcQL/7YpFzndO+yj9/9SRxKOm/1zBPtAyNU=; b=aImOHYRHjfSVgHyEY//nzY7lyNIQkOAv8bAEcxHrSdPEtCcF7+vaQC364QhiUEGbRY 0S/VZql7ZIT7rDmHja6BSR2kCu3y6ccJPJgqR3iQs8BdkmY/1qJgyXD7WsGWfLOXJtI8 62R21MwPBq2noPNeQJQGjRWic+Khvo31146Qrm88a61KOK6a7+qfzugkn55zHK371wbv BVoDRan+xXt5yfQirWKzm4JrdR//lZgK52zrwO+amZqhx7L1ZtxNjBSPBlcgD+Yz4uVA i6IzZ/8Mr2b+B2qlGv4jhQ6sXH09LCQDxCYwY0XTQSKR1MG7+2rUQRWV/rwRVBMBTI4h /VCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=piepAd/SOcQL/7YpFzndO+yj9/9SRxKOm/1zBPtAyNU=; b=k6GzeUXMhRc4KS/iHm0Pboz0n3zj+2BVKwbZ6fBj7vhx7HELDs4Z8+Kjwx0WqpZV/h xDyflD2WHhULoz3eqVJX4bKG4sj9YwQgh4+btw7yOWRYmGhSQ+T4Gh1lLosypD8JFEQs bm/4nRHJNai078HHN8yii4WVFFEsIC9sZmGwqCIQC/ltl/B+7hK8OujpiR4rexQlBGsL REftmx1iYrtlfHaGoCgXfAecOuzzfRvUJZkwGbQtnqoatModsPha4ecmbGe/cG72lCFQ PUngiM/7Q/dpPje8tJoHNjTkBPAdV74p1OqA9sd9vhl3IJ0ZdYVrq+xIl3dOnsW4qgow uJGQ== X-Gm-Message-State: AOAM533SrZAKPDrl6gKXXIiwsyslYFphomqExAFRo76Rwx1K2sVwswnv p15rthBuGYGgO4F950g8FZWPWaPhesKFhgcG X-Google-Smtp-Source: ABdhPJz6Sv4h9V/euaaE4EbAIs9KqichrRM8CcR6WfGkY7yI9Q5IRIxqZblSNAHYlHDIjtkRPg58HA== X-Received: by 2002:a2e:9812:: with SMTP id a18mr12401139ljj.73.1608050492403; Tue, 15 Dec 2020 08:41:32 -0800 (PST) Received: from localhost.localdomain (109-252-202-142.dynamic.spd-mgts.ru. [109.252.202.142]) by smtp.gmail.com with ESMTPSA id y3sm263287lfy.73.2020.12.15.08.41.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Dec 2020 08:41:31 -0800 (PST) From: Sergey Temerkhanov To: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Sergey Temerkhanov Subject: [PATCH] fget: Do not loop with rcu lock held Date: Tue, 15 Dec 2020 19:41:23 +0300 Message-Id: <20201215164123.609980-1-s.temerkhanov@gmail.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Unlock RCU before running another loop iteration Signed-off-by: Sergey Temerkhanov --- fs/file.c | 34 ++++++++++++++++++++-------------- 1 file changed, 20 insertions(+), 14 deletions(-) diff --git a/fs/file.c b/fs/file.c index 4559b5fec3bd..49d57752e7a6 100644 --- a/fs/file.c +++ b/fs/file.c @@ -823,21 +823,27 @@ static struct file *__fget_files(struct files_struct *files, unsigned int fd, fmode_t mask, unsigned int refs) { struct file *file; + bool again = false; - rcu_read_lock(); -loop: - file = fcheck_files(files, fd); - if (file) { - /* File object ref couldn't be taken. - * dup2() atomicity guarantee is the reason - * we loop to catch the new file (or NULL pointer) - */ - if (file->f_mode & mask) - file = NULL; - else if (!get_file_rcu_many(file, refs)) - goto loop; - } - rcu_read_unlock(); + do { + rcu_read_lock(); + + file = fcheck_files(files, fd); + if (file) { + /* File object ref couldn't be taken. + * dup2() atomicity guarantee is the reason + * we loop to catch the new file (or NULL pointer) + */ + if (file->f_mode & mask) + file = NULL; + else if (!get_file_rcu_many(file, refs)) + again = true; + } + rcu_read_unlock(); + + if (unlikely(again)) + schedule(); + } while (again); return file; } -- 2.25.1