From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [RFC][PATCH 7/8]: Auto-create ptmx node when mounting devpts Date: Thu, 21 Aug 2008 09:09:19 -0700 Message-ID: <48AD932F.8090908@zytor.com> References: <20080821022126.GA29449@us.ibm.com> <20080821022908.GG29658@us.ibm.com> <20080821102139.43c44f67@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20080821102139.43c44f67-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Alan Cox Cc: kyle-hoO6YkzgTuCM0SS3m2neIg@public.gmane.org, bastian-yyjItF7Rl6lg9hUCZPvPmw@public.gmane.org, containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org, ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org List-Id: containers.vger.kernel.org Alan Cox wrote: >> This patch has the kernel internally create the [ptmx, c, 5:2] device >> when mounting devpts filesystem. The permissions for the device node >> can be specified by the '-o ptmx_mode=0666' option. The default mode >> is 0666. > > NAK > >> Hopefully, presence of the 'ptmx' node in /dev/pts does not surprise >> user space. > > If you are going to make major changes requiring user space changes to > use them then you can change the user space rather than playing "gee > where did that come from" with the existing system. > This particular one I think is the right thing, despite everything. In particular, it makes a *hell* of a lot more sense to have this auto-created, than supporting mknod(2) inside the devpts filesystem. It's not a matter of "changing the user space"; it's a matter of what makes most sense inside the kernel. His new implementation doesn't require user space changes unless you want to take advantages of the multi-instance features. It thus allows for a soft transition. However, soft or hard transition is irrelevant -- creating ptmx inside devpts is necessary, and it doesn't make sense to require userspace to mknod it, since the kernel code ends up being more complex. -hpa