From patchwork Wed Feb 1 10:44:48 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9549299 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id F362160425 for ; Wed, 1 Feb 2017 10:45:36 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0221D27D85 for ; Wed, 1 Feb 2017 10:45:37 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EB3AC281E1; Wed, 1 Feb 2017 10:45:36 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id A36C027D85 for ; Wed, 1 Feb 2017 10:45:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751703AbdBAKpe (ORCPT ); Wed, 1 Feb 2017 05:45:34 -0500 Received: from mx2.suse.de ([195.135.220.15]:46392 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751548AbdBAKpS (ORCPT ); Wed, 1 Feb 2017 05:45:18 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id CE5CAAAA3; Wed, 1 Feb 2017 10:45:15 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id AFD461E3428; Wed, 1 Feb 2017 11:45:11 +0100 (CET) From: Jan Kara To: Cc: Amir Goldstein , Paul Moore , Miklos Szeredi , Jan Kara Subject: [PATCH 16/25] fanotify: Release SRCU lock when waiting for userspace response Date: Wed, 1 Feb 2017 11:44:48 +0100 Message-Id: <20170201104457.23194-17-jack@suse.cz> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20170201104457.23194-1-jack@suse.cz> References: <20170201104457.23194-1-jack@suse.cz> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When userspace task processing fanotify permission events screws up and does not respond, fsnotify_mark_srcu SRCU is held indefinitely which causes further hangs in the whole notification subsystem. Although we cannot easily solve the problem of operations blocked waiting for response from userspace, we can at least somewhat localize the damage by dropping SRCU lock before waiting for userspace response and reacquiring it when userspace responds. Reviewed-by: Amir Goldstein Signed-off-by: Jan Kara --- fs/notify/fanotify/fanotify.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c index cc2763300914..210b7df2586b 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -61,14 +61,26 @@ static int fanotify_merge(struct list_head *list, struct fsnotify_event *event) #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS static int fanotify_get_response(struct fsnotify_group *group, - struct fanotify_perm_event_info *event) + struct fanotify_perm_event_info *event, + struct fsnotify_iter_info *iter_info) { int ret; pr_debug("%s: group=%p event=%p\n", __func__, group, event); + /* + * fsnotify_prepare_user_wait() fails if we race with mark deletion. + * Just let the operation pass in that case. + */ + if (!fsnotify_prepare_user_wait(iter_info)) { + event->response = FAN_ALLOW; + goto out; + } + wait_event(group->fanotify_data.access_waitq, event->response); + fsnotify_finish_user_wait(iter_info); +out: /* userspace responded, convert to something usable */ switch (event->response) { case FAN_ALLOW: @@ -220,7 +232,8 @@ static int fanotify_handle_event(struct fsnotify_group *group, #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS if (mask & FAN_ALL_PERM_EVENTS) { - ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event)); + ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event), + iter_info); fsnotify_destroy_event(group, fsn_event); } #endif