lib9p: added functions for devshr

1 files changed, 50 insertions, 0 deletions

diff --git a/sys/src/lib9p/post.c b/sys/src/lib9p/post.c
index b42c7b32c..37dcfd5dc 100644
--- a/sys/src/lib9p/post.c
+++ b/sys/src/lib9p/post.c
@@ -56,6 +56,56 @@ _postmountsrv(Srv *s, char *name, char *mtpt, int flag)
 		close(s->srvfd);
 }
 
+void
+_postsharesrv(Srv *s, char *name, char *mtpt, char *desc, char *flag)
+{
+	int fd[2];
+
+	if(!s->nopipe){
+		if(pipe(fd) < 0)
+			sysfatal("pipe: %r");
+		s->infd = s->outfd = fd[1];
+		s->srvfd = fd[0];
+	}
+	if(name)
+		if(postfd(name, s->srvfd) < 0)
+			sysfatal("postfd %s: %r", name);
+
+	if(_forker == nil)
+		sysfatal("no forker");
+	_forker(postproc, s, RFNAMEG);
+
+	/*
+	 * Normally the server is posting as the last thing it does
+	 * before exiting, so the correct thing to do is drop into
+	 * a different fd space and close the 9P server half of the
+	 * pipe before trying to mount the kernel half.  This way,
+	 * if the file server dies, we don't have a ref to the 9P server
+	 * half of the pipe.  Then killing the other procs will drop
+	 * all the refs on the 9P server half, and the mount will fail.
+	 * Otherwise the mount hangs forever.
+	 *
+	 * Libthread in general and acme win in particular make
+	 * it hard to make this fd bookkeeping work out properly,
+	 * so leaveinfdopen is a flag that win sets to opt out of this
+	 * safety net.
+	 */
+	if(!s->leavefdsopen){
+		rfork(RFFDG);
+		rendezvous(0, 0);
+		close(s->infd);
+		if(s->infd != s->outfd)
+			close(s->outfd);
+	}
+
+	if(mtpt){
+		if(sharefd(mtpt, desc, flag, s->srvfd) < 0)
+			sysfatal("sharefd %s: %r", mtpt);
+	}else
+		close(s->srvfd);
+}
+
+
 static void
 postproc(void *v)
 {