proposed relayfs changes and systemtap

[Tom Zanussi <zanussi at us dot ibm dot com>]

Hi,

Someone over the weekend posted a patch to remove the filesystem part
of relayfs and instead have applications' relayfs files live in other
filesytems instead:

http://marc.theaimsgroup.com/?l=linux-kernel&m=114036950922176&w=2

It looks like there's support for making this change (this idea has
come up multiple times before and I thought it made sense then too,
but it's never really gotten legs until now).

Anyway, in case anyone was worrying about how it would affect
systemtap, not much.  The poster of the patches has concentrated on
using sysfs to house relay files, but since systemtap already uses
/proc, it would seem to make sense for systemtap to move its relay
files there instead.

So, assuming we want move things over to procfs, the changes that
would need to be made for systemtap would be:

1) runtime/transport/relayfs.c - add file creation/removal relayfs
   callback handlers.  These will create/remove the proc files to
   represent the relayfs buffers.

2) runtime/transport/relayfs.c - change the relayfs_create_dir() and
   relayfs_remove_dir() calls to their procfs counterparts.

3) runtime/stpd/stpd.c - change "/mnt/relay" to "/proc" in main()

So that's it - the changes would be pretty minimal, and of course I'll
be happy to make them.

Tom