From patchwork Wed Mar 15 10:46:23 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 9625273 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 C2C9160424 for ; Wed, 15 Mar 2017 10:47:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C1C4828173 for ; Wed, 15 Mar 2017 10:47:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id B6A95282E8; Wed, 15 Mar 2017 10:47:15 +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 6A1FA28173 for ; Wed, 15 Mar 2017 10:47:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753367AbdCOKrN (ORCPT ); Wed, 15 Mar 2017 06:47:13 -0400 Received: from mx2.suse.de ([195.135.220.15]:36554 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753233AbdCOKqr (ORCPT ); Wed, 15 Mar 2017 06:46:47 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 3B193AE13; Wed, 15 Mar 2017 10:46:43 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id E67F61E1259; Wed, 15 Mar 2017 11:46:39 +0100 (CET) From: Jan Kara To: Cc: Miklos Szeredi , Amir Goldstein , Paul Moore , Jan Kara Subject: [PATCH 24/33] fanotify: Release SRCU lock when waiting for userspace response Date: Wed, 15 Mar 2017 11:46:23 +0100 Message-Id: <20170315104632.7037-25-jack@suse.cz> X-Mailer: git-send-email 2.10.2 In-Reply-To: <20170315104632.7037-1-jack@suse.cz> References: <20170315104632.7037-1-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 ec80a51cbb3d..461c21ebebeb 100644 --- a/fs/notify/fanotify/fanotify.c +++ b/fs/notify/fanotify/fanotify.c @@ -57,14 +57,26 @@ 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: @@ -216,7 +228,8 @@ 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