From mboxrd@z Thu Jan  1 00:00:00 1970
To: 9fans@cse.psu.edu
Subject: Re: [9fans] Two ramfs?
From: "Russ Cox" <rsc@swtch.com>
Date: Mon,  4 Feb 2008 15:34:52 -0500
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> 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