Re: [PATCH 11/11][v3]: Enable multiple instances of devpts

[sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org]

H. Peter Anvin [hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org] wrote:
> sukadev-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org wrote:
>> Agree in general. Not sure if you are implying remount is necessary just
>> to change permissions of pts/ptmx. Why not "chmod 0666 /dev/pts/ptmx" ?
>> The remount changes the 'ptmxmode' setting, but since the node exists,
>> the 'ptmxmode' setting is never used again and we need to chmod.
>
> A chmod requires bigger changes to existing scripts than an option which 
> can be set in /etc/fstab.

Ok. From implementation pov, we can cache the ptmx dentry in s_fs_info
and use it during remount to change the permissions. We could lookup
ptmx during remount, but caching is simpler ?

>
>> ptmx node in multi-instance mounts continue to get PTMX_DEFAULT_MODE
>> permissions (not 000) right ? (unless -o ptmxmode is specified)
>
> It's probably easier to always default it to zero and expect that the mode 
> is set explicitly.

Ok.

BTW, I have added CONFIG_DEVPTS_MULTIPLE_INSTANCES and moved the usage
info from 11/11 to Documentation/fs/devpts.txt.

Will make above ptmx changes, port to recent ttydev tree and send updated
patchset in a couple of days.

Thanks,

suka