Re: [9fans] Two ramfs?

["Lluís Batlle" <viriketo@gmail.com>]

Hello Russ,

before trying to code something from scrach using createfile & co., I
wanted to get ramfs working (that of lib9p/, the only example of
Tree/File I found in plan9port). After your fix related to a proper
unmount/remount, now I see that the 9pserve process exits hardly if I
try to create a file in the ramfs filesystem. It doesn't die because
of a signal. I tried gdb on it, breakpointing at exits/threadexits,
but I don't understand the makecontext() game of libthread. I put a
stderr trace in the fscreate() function of ramfs.c, and it doesn't
even appear. I guess fscreate() is not called.

Maybe that part of the lib9p api is generally broken/not-tested?

Thank you,
Lluís.

2008/2/4, Russ Cox <rsc@swtch.com>:
> > I saw the src/cmd/ramfs.c, and I think I should be able to write mine
> > simpler... For example, I'd like to take advantage of the File/Tree
> > interface (createfile(), ...), having all the files of the fs in
> > memory.
> >
> > I found also src/lib9p/ramfs.c, which looks pretty much as what I
> > want, but this doesn't tollerate remounting well at all (I guess).
> >
> > I tried it with some modifications (to get it compiled) in plan9port
> > over linux (./ramfs -D -s test)  and two "9p ls test" in a row makes
> > the server die.
> >
> > Where can I see an example of a working fileserver which uses File,
> > Tree, and the related functions?
>
> It's been a long time since I looked at that code, but it appears
> that the problem is that Tattach doesn't increment the reference
> count on its directory.  Reattaching isn't very common in Plan 9
> (but is on p9p) so it's easy to believe this bug went unnoticed.
>
> Here is the fix, now in p9p:
>
> diff -r bcad073690c5 src/lib9p/srv.c
> --- a/src/lib9p/srv.c   Fri Feb 01 07:54:19 2008 -0500
> +++ b/src/lib9p/srv.c   Mon Feb 04 15:32:28 2008 -0500
> @@ -227,7 +227,7 @@ sattach(Srv *srv, Req *r)
>         r->fid->uid = estrdup9p(r->ifcall.uname);
>         if(srv->tree){
>                 r->fid->file = srv->tree->root;
> -               /* BUG? incref(r->fid->file) ??? */
> +               incref(&r->fid->file->ref);
>                 r->ofcall.qid = r->fid->file->dir.qid;
>                 r->fid->qid = r->ofcall.qid;
>         }
>
> Russ
>
>