interpret some ctl messages to make managmenet easier;
exit on kill or exit message.

Reference: /n/atom/patch/applied2013/snapfsctl
Date: Wed Jun 19 01:18:46 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/snap/snapfs.c	Wed Jun 19 01:18:43 2013
+++ /sys/src/cmd/snap/snapfs.c	Wed Jun 19 01:18:43 2013
@@ -7,12 +7,23 @@
 #include <9p.h>
 #include "snap.h"
 
+static char *textfile;
+static void *rend;
+
+enum{
+	Xproc,
+	Xdata,
+	Xfd,
+	Xctl,
+};
+
 typedef struct PD PD;
 struct PD {
-	int isproc;
+	uchar type;
 	union {
-		Proc *p;
-		Data *d;
+		Proc	*p;
+		Data	*d;
+		int	fd;
 	};
 };
 
@@ -21,8 +32,8 @@
 {
 	PD *pd;
 
-	pd = emalloc(sizeof(*pd));
-	pd->isproc = 1;
+	pd = emalloc(sizeof *pd);
+	pd->type = Xproc;
 	pd->p = p;
 	return pd;
 }
@@ -32,16 +43,37 @@
 {
 	PD *pd;
 
-	pd = emalloc(sizeof(*pd));
-	pd->isproc = 0;
+	pd = emalloc(sizeof *pd);
+	pd->type = Xdata;
 	pd->d = d;
 	return pd;
 }
 
+PD*
+PDFd(int fd)
+{
+	PD *pd;
+
+	pd = emalloc(sizeof *pd);
+	pd->type = Xfd;
+	pd->fd = fd;
+	return pd;
+};
+
+PD*
+PDctl(void)
+{
+	PD *pd;
+
+	pd = emalloc(sizeof *pd);
+	pd->type = Xctl;
+	return pd;
+};
+
 void
 usage(void)
 {
-	fprint(2, "usage: snapfs [-a] [-m mtpt] file\n");
+	fprint(2, "usage: snapfs [-a] [-t dbg text] [-m mtpt] file\n");
 	exits("usage");
 }
 
@@ -57,7 +89,6 @@
 
 	if(*count > Pagesize-po)
 		*count = Pagesize-po;
-
 	memmove(buf, pg->data+po, *count);
 	return nil;
 }
@@ -82,7 +113,7 @@
 void
 fsread(Req *r)
 {
-	char *e;
+	char *e, buf[ERRMAX];
 	PD *pd;
 	Fid *fid;
 	void *data;
@@ -95,18 +126,60 @@
 	count = r->ifcall.count;
 	pd = fid->file->aux;
 
-	if(pd->isproc)
+	e = nil;
+	switch(pd->type){
+	case Xproc:
 		e = memread(pd->p, fid->file, data, &count, offset);
-	else
+		break;
+	case Xdata:
 		e = dataread(pd->d, data, &count, offset);
-
+		break;
+	case Xfd:
+		count = pread(pd->fd, data, count, offset);
+		if(count == -1){
+			errstr(buf, sizeof buf);
+			e = buf;
+		}else
+			e = nil;
+		break;
+	case Xctl:
+		e = "not implemented";
+		break;
+	}
 	if(e == nil)
 		r->ofcall.count = count;
 	respond(r, e);
 }
 
+void
+fswrite(Req *r)
+{
+	char *e;
+	PD *pd;
+
+	e = "permission denied";
+	pd = r->fid->file->aux;
+	switch(pd->type){
+	default:
+		break;
+	case Xctl:
+		if(!strncmp(r->ifcall.data, "debug", 5)){
+			e = nil;
+			debug ^= 1;
+		}else if(strncmp(r->ifcall.data, "kill", 4) == 0
+		|| strncmp(r->ifcall.data, "exit", 4) == 0){
+			respond(r, nil);
+			rendezvous(&rend, 0);
+			return;
+		}
+		break;
+	}
+	respond(r, e);
+}
+		
 Srv fs = {
 	.read = fsread,
+	.write = fswrite,
 };
 
 File*
@@ -121,7 +194,15 @@
 }
 
 void
-main(int argc, char **argv)
+cleanup(void*)
+{
+	rendezvous(&rend, 0);
+	bind("#p", "/proc", MREPL);
+	threadexitsall("");
+}
+
+void
+threadmain(int argc, char **argv)
 {
 	Biobuf *b;
 	Data *d;
@@ -129,7 +210,7 @@
 	Proc *p, *plist;
 	Tree *tree;
 	char *mtpt, buf[32];
-	int i, mflag;
+	int i, mflag, fd;
 
 	mtpt = "/proc";
 	mflag = MBEFORE;
@@ -145,7 +226,10 @@
 		mflag = MAFTER;
 		break;
 	case 'm':
-		mtpt = ARGF();
+		mtpt = EARGF(usage());
+		break;
+	case 't':
+		textfile = EARGF(usage());
 		break;
 	default:
 		usage();
@@ -173,11 +257,16 @@
 
 		snprint(buf, sizeof buf, "%ld", p->pid);
 		fdir = ecreatefile(tree->root, buf, nil, DMDIR|0555, nil);
-		ecreatefile(fdir, "ctl", nil, 0777, nil);
-		if(p->text)
-			ecreatefile(fdir, "text", nil, 0777, PDProc(p));
-
+		ecreatefile(fdir, "ctl", nil, 0666, PDctl());
 		ecreatefile(fdir, "mem", nil, 0666, PDProc(p));
+		if(textfile){
+			fd = open(textfile, OREAD);
+			if(fd == -1)
+				sysfatal("open: %r");
+			f = ecreatefile(fdir, "text", nil, 0444, PDFd(fd));
+			f->length = seek(fd, 0, 2);
+		}else if(p->text)
+			ecreatefile(fdir, "text", nil, 0777, PDProc(p));
 		for(i=0; i<Npfile; i++) {
 			if(d = p->d[i]) {
 				f = ecreatefile(fdir, pfile[i], nil, 0666, PDData(d));
@@ -186,6 +275,7 @@
 		}
 	}
 
-	postmountsrv(&fs, nil, mtpt, mflag);
-	exits(0);
+	proccreate(cleanup, nil, 8192);
+	threadpostmountsrv(&fs, nil, mtpt, mflag);
+	exits("");
 }