Linus Torvalds <torva...@linux-foundation.org> writes: > On Fri, Apr 15, 2016 at 8:35 AM, Eric W. Biederman > <ebied...@xmission.com> wrote: >> The devpts filesystem has a notion of a system or primary instance of >> devpts. To retain the notion of a primary system instance of devpts >> the code needs a way to allow userspace to mount the internally >> mounted instance of devpts when it is not currently mounted by >> userspace. The new helper mount_super_once allows that. > > This is where I stopped reading this patch series. > > No. > > We want to get *rid* of the idiotic "primary instance" crap.
That is actually pretty much the opposite of what you said last time, but having looked at the cost to maintian a "primary instance" notion and what will break if we don't I am happy to remove such a notion from devpts. > The whole and only point of doing the "which pts filesystem am I > associated with" for ptmx is to stop the idiotic "one devpts is > pecial". > > I don't want to see 16 random patches. > > I want to see *one* patch that makes /dev/ptmx look up the pts > filesystem, and be done with it. Now that I know where most of the landmines are in userspace I performed some limited testing to see to see what the implications are: Causing every userspace mount of devpts to use mount_nodev means the following: - Support for reserving ptys for the system devpts instance using /proc/sys/kernel/pty/reserve needs to be removed. - On CentOS6 devpts will wind up mounted twice /dev/pts. - Open of /dev/ptmx can use devpts_mnt to find the devpts filesystem. In my cursory testing userspace still boots and works desipite those changes so I am quite happy to go down this path. Eric