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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 37B9BC2D0C0 for ; Mon, 23 Dec 2019 21:26:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11260206D3 for ; Mon, 23 Dec 2019 21:26:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726893AbfLWV0v (ORCPT ); Mon, 23 Dec 2019 16:26:51 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:40144 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726817AbfLWV0v (ORCPT ); Mon, 23 Dec 2019 16:26:51 -0500 Received: from p5b2a6d78.dip0.t-ipconnect.de ([91.42.109.120] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1ijVDz-0003a4-Q4; Mon, 23 Dec 2019 21:26:47 +0000 Date: Mon, 23 Dec 2019 22:26:46 +0100 From: Christian Brauner To: Sargun Dhillon Cc: linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, tycho@tycho.ws, jannh@google.com, cyphar@cyphar.com, oleg@redhat.com, luto@amacapital.net, viro@zeniv.linux.org.uk, gpascutto@mozilla.com, ealvarez@mozilla.com, fweimer@redhat.com, jld@mozilla.com, arnd@arndb.de Subject: Re: [PATCH v6 1/3] vfs, fdtable: Add get_task_file helper Message-ID: <20191223212645.3qw7my4u4rjihxjf@wittgenstein> References: <20191223210852.GA25101@ircssh-2.c.rugged-nimbus-611.internal> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20191223210852.GA25101@ircssh-2.c.rugged-nimbus-611.internal> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 23, 2019 at 09:08:55PM +0000, Sargun Dhillon wrote: > This introduces a function which can be used to fetch a file, given an > arbitrary task. As long as the user holds a reference (refcnt) to the > task_struct it is safe to call, and will either return NULL on failure, > or a pointer to the file, with a refcnt. > > Signed-off-by: Sargun Dhillon > --- > fs/file.c | 22 ++++++++++++++++++++-- > include/linux/file.h | 2 ++ > 2 files changed, 22 insertions(+), 2 deletions(-) > > diff --git a/fs/file.c b/fs/file.c > index 2f4fcf985079..0ceeb046f4f3 100644 > --- a/fs/file.c > +++ b/fs/file.c > @@ -706,9 +706,9 @@ void do_close_on_exec(struct files_struct *files) > spin_unlock(&files->file_lock); > } > > -static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs) > +static struct file *__fget_files(struct files_struct *files, unsigned int fd, > + fmode_t mask, unsigned int refs) > { > - struct files_struct *files = current->files; > struct file *file; > > rcu_read_lock(); > @@ -729,6 +729,11 @@ static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs) > return file; > } > > +static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs) > +{ > + return __fget_files(current->files, fd, mask, refs); > +} > + > struct file *fget_many(unsigned int fd, unsigned int refs) > { > return __fget(fd, FMODE_PATH, refs); > @@ -746,6 +751,19 @@ struct file *fget_raw(unsigned int fd) > } > EXPORT_SYMBOL(fget_raw); > > +struct file *fget_task(struct task_struct *task, unsigned int fd) > +{ > + struct file *file = NULL; > + > + task_lock(task); > + if (task->files) > + file = __fget_files(task->files, fd, 0, 1); > + > + task_unlock(task); Nit: remove the \n: task_lock(task); if (task->files) file = __fget_files(task->files, fd, 0, 1); task_unlock(task); Christian