Re: [9fans] v9fs question

[Eric Van Hensbergen <ericvh@gmail.com>]

On Jul 14, 2009, at 6:08 AM, roger peppe <rogpeppe@gmail.com> wrote:

> this is at a bit of a tangent from the previous discussion,
> but something i've always wondered:
>
> why does the linux 9p mount syscall bother
> with IP addresses at all? isn't it sufficient
> just to provide a facility for mounting a file descriptor
> (like the plan 9 syscall) and have an auxiliary
> command do the actual dial, authentication, etc?
>

This has always been an option.  The tcp transport is there (and is
default) because it is closest to the expected behavior for the naive
Linux user.  It is also there because at one time we used 9p as root
(ala nfsroot direct option in the kernel).

It's worth noting there are performance/efficency implications for
using the fd transport (particularly for the non-socket fd case like
sshsrv) as well as the unix named pipes transport -- but I don't have
quantitative analysis of the differences as it's hard to get an apples
to apples comparison.   Anthony ligouri has shown some really
promising numbers for a hybrid transport based on the Linux splice
command.

> wouldn't that be simpler

The code in question is mostly common, maybe 20 lines of code for each
tcp and unix, so I think it's worth having them as options so that
user space mount tools arent required.