From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754151AbaCaSCl (ORCPT ); Mon, 31 Mar 2014 14:02:41 -0400 Received: from mail-la0-f52.google.com ([209.85.215.52]:58168 "EHLO mail-la0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753563AbaCaSCj (ORCPT ); Mon, 31 Mar 2014 14:02:39 -0400 Date: Mon, 31 Mar 2014 22:02:37 +0400 From: Cyrill Gorcunov To: linux-kernel@vger.kernel.org Cc: shawn@churchofgit.com, tglx@linutronix.de, akpm@linux-foundation.org, avagin@openvz.org, xemul@parallels.com Subject: [rfc ] timerfd: Implement write method Message-ID: <20140331180237.GL4872@moon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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 The read() of timerfd files allows to fetch the number of timer ticks while there is no way to set it back from userspace. To restore the timer state as it was at checkpoint moment we need a way to setup ticks back. So as a counterpart of read() the write() takes ticks number from the userspace and updates internal timer ticks accordingly. CC: Shawn Landden CC: Thomas Gleixner CC: Andrew Morton CC: Andrey Vagin CC: Pavel Emelyanov Signed-off-by: Cyrill Gorcunov --- This is a third patch in the series, I've screwed quilt mail command. fs/timerfd.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) Index: linux-2.6.git/fs/timerfd.c =================================================================== --- linux-2.6.git.orig/fs/timerfd.c +++ linux-2.6.git/fs/timerfd.c @@ -292,10 +292,31 @@ static int timerfd_show(struct seq_file ctx->clockid, (unsigned long long)ctx->ticks); } + +static ssize_t timerfd_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct timerfd_ctx *ctx = file->private_data; + u64 ticks = 0; + + if (count < sizeof(ticks)) + return -EINVAL; + + if (get_user(ticks, (u64 __user *) buf)) + return -EFAULT; + + spin_lock_irq(&ctx->wqh.lock); + ctx->ticks = ticks; + spin_unlock_irq(&ctx->wqh.lock); + + return sizeof(ticks); +} + static const struct file_operations timerfd_fops = { .release = timerfd_release, .poll = timerfd_poll, .read = timerfd_read, + .write = timerfd_write, .llseek = noop_llseek, .show_fdinfo = timerfd_show, };