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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 993D7C433B4 for ; Mon, 19 Apr 2021 10:22:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66F0861165 for ; Mon, 19 Apr 2021 10:22:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238511AbhDSKXI (ORCPT ); Mon, 19 Apr 2021 06:23:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:60582 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238537AbhDSKW7 (ORCPT ); Mon, 19 Apr 2021 06:22:59 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3D2B7B2E6; Mon, 19 Apr 2021 10:21:39 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 0B61F1F2C6A; Mon, 19 Apr 2021 12:21:39 +0200 (CEST) Date: Mon, 19 Apr 2021 12:21:39 +0200 From: Jan Kara To: Matthew Bobrowski Cc: jack@suse.cz, amir73il@gmail.com, christian.brauner@ubuntu.com, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 2/2] fanotify: Add pidfd support to the fanotify API Message-ID: <20210419102139.GD8706@quack2.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri 16-04-21 09:22:25, Matthew Bobrowski wrote: > Introduce a new flag FAN_REPORT_PIDFD for fanotify_init(2) which > allows userspace applications to control whether a pidfd is to be > returned instead of a pid for `struct fanotify_event_metadata.pid`. > > FAN_REPORT_PIDFD is mutually exclusive with FAN_REPORT_TID as the > pidfd API is currently restricted to only support pidfd generation for > thread-group leaders. Attempting to set them both when calling > fanotify_init(2) will result in -EINVAL being returned to the > caller. As the pidfd API evolves and support is added for tids, this > is something that could be relaxed in the future. > > If pidfd creation fails, the pid in struct fanotify_event_metadata is > set to FAN_NOPIDFD(-1). Falling back and providing a pid instead of a > pidfd on pidfd creation failures was considered, although this could > possibly lead to confusion and unpredictability within userspace > applications as distinguishing between whether an actual pidfd or pid > was returned could be difficult, so it's best to be explicit. > > Signed-off-by: Matthew Bobrowski Overall this looks OK to me. Just one style nit & one question below in addition to what Amir wrote. > --- > fs/notify/fanotify/fanotify_user.c | 33 +++++++++++++++++++++++++++--- > include/linux/fanotify.h | 2 +- > include/uapi/linux/fanotify.h | 2 ++ > 3 files changed, 33 insertions(+), 4 deletions(-) > > diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c > index 9e0c1afac8bd..fd8ae88796a8 100644 > --- a/fs/notify/fanotify/fanotify_user.c > +++ b/fs/notify/fanotify/fanotify_user.c > @@ -329,7 +329,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, > struct fanotify_info *info = fanotify_event_info(event); > unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS); > struct file *f = NULL; > - int ret, fd = FAN_NOFD; > + int ret, pidfd, fd = FAN_NOFD; > int info_type = 0; > > pr_debug("%s: group=%p event=%p\n", __func__, group, event); > @@ -340,7 +340,25 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, > metadata.vers = FANOTIFY_METADATA_VERSION; > metadata.reserved = 0; > metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS; > - metadata.pid = pid_vnr(event->pid); > + > + if (FAN_GROUP_FLAG(group, FAN_REPORT_PIDFD) && > + pid_has_task(event->pid, PIDTYPE_TGID)) { Please align the rest of the condition to the opening brace. I.e., like: if (FAN_GROUP_FLAG(group, FAN_REPORT_PIDFD) && pid_has_task(event->pid, PIDTYPE_TGID)) { BTW, why is the pid_has_task() check here? And why is it OK to fall back to returning pid if pid_has_task() is false? Honza -- Jan Kara SUSE Labs, CR