From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752202Ab3FZQSi (ORCPT ); Wed, 26 Jun 2013 12:18:38 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55016 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751285Ab3FZQSh (ORCPT ); Wed, 26 Jun 2013 12:18:37 -0400 Date: Wed, 26 Jun 2013 11:18:20 -0500 From: Serge Hallyn To: linux-kernel@vger.kernel.org Cc: Eric Biederman , "Daniel P. Berrange" , containers@lists.linux-foundation.org, Colin Ian King , =?iso-8859-1?Q?St=E9phane?= Graber Subject: [PATCH RFC] procfs: add pidnr file Message-ID: <20130626161820.GA32142@tp> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a file called pidnr under /proc/task/. Reading this file gives the pid of /proc/task in the reading task's namespace (or 0 if there is no valid pid). This fills a need currently not solvable at all. The particular need I have for it is so that a task inside a container can pass requests to a task outside the container (using an open fd for /proc/task) to have the target task moved to a new cgroup. Others have asked for this ability for other reasons. Signed-off-by: Serge Hallyn Cc: Eric Biederman Cc: "Daniel P. Berrange" Cc: containers@lists.linux-foundation.org Cc: Colin Ian King Cc: Stéphane Graber --- fs/proc/base.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index c3834da..b7499eb 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -899,6 +899,28 @@ static const struct file_operations proc_environ_operations = { .release = mem_release, }; +#define TMPBUFLEN 21 +static ssize_t pidnr_read(struct file * file, char __user * buf, + size_t count, loff_t *ppos) +{ + struct inode * inode = file_inode(file); + struct task_struct *task = get_proc_task(inode); + ssize_t length; + char tmpbuf[TMPBUFLEN]; + + if (!task) + return -ESRCH; + length = scnprintf(tmpbuf, TMPBUFLEN, "%u\n", + task_pid_vnr(task)); + put_task_struct(task); + return simple_read_from_buffer(buf, count, ppos, tmpbuf, length); +} + +static const struct file_operations pidnr_operations = { + .read = pidnr_read, + .llseek = generic_file_llseek, +}; + static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -1096,7 +1118,6 @@ static const struct file_operations proc_oom_score_adj_operations = { }; #ifdef CONFIG_AUDITSYSCALL -#define TMPBUFLEN 21 static ssize_t proc_loginuid_read(struct file * file, char __user * buf, size_t count, loff_t *ppos) { @@ -2642,6 +2663,7 @@ static const struct pid_entry tgid_base_stuff[] = { DIR("net", S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations), #endif REG("environ", S_IRUSR, proc_environ_operations), + REG("pidnr", S_IRUGO, pidnr_operations), INF("auxv", S_IRUSR, proc_pid_auxv), ONE("status", S_IRUGO, proc_pid_status), ONE("personality", S_IRUGO, proc_pid_personality), @@ -2999,6 +3021,7 @@ static const struct pid_entry tid_base_stuff[] = { DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations), REG("environ", S_IRUSR, proc_environ_operations), + REG("pidnr", S_IRUGO, pidnr_operations), INF("auxv", S_IRUSR, proc_pid_auxv), ONE("status", S_IRUGO, proc_pid_status), ONE("personality", S_IRUGO, proc_pid_personality), -- 1.7.9.5