From 8c137149bd54a9bba8026ddf4bc4f49f7ccbb404 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 20 Jan 1999 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1999-01-20

---
 port/error.h   |  1 +
 port/fault.c   | 21 ++++++++++++++-------
 port/portfns.h |  1 +
 port/segment.c | 23 +++++++++++++++++++++++
 port/swap.c    | 15 +++++++++++++--
 5 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/port/error.h b/port/error.h
index 6f123a2ea6f36214654a0c496b5a01753272e3b3..6cc752c0d9e1e7e0525c754cc252081b324000fb 100644
--- a/port/error.h
+++ b/port/error.h
@@ -46,6 +46,7 @@ extern char Enetunreach[];	/* network unreachable */
 extern char Eintr[];		/* interrupted */
 extern char Eneedservice[];	/* service required for tcp/udp/il calls */
 extern char Enomem[];		/* kernel allocate failed */
+extern char Enoswap[];		/* swap space full */
 extern char Esfnotcached[];	/* subfont not cached */
 extern char Esoverlap[];	/* segments overlap */
 extern char Emouseset[];	/* mouse type already set */
diff --git a/port/fault.c b/port/fault.c
index 9b8b342ff29e3b43d70b3753bae2b52f4864b86e..131b65f462b0b3a12fbae4ec92cb03eeb938b42d 100644
--- a/port/fault.c
+++ b/port/fault.c
@@ -38,13 +38,13 @@ fault(ulong addr, int read)
 }
 
 static void
-faulterror(char *s)
+faulterror(char *s, int freemem)
 {
 	if(up->nerrlab) {
 		postnote(up, 1, s, NDebug);
 		error(s);
 	}
-	pexit(s, 0);
+	pexit(s, freemem);
 }
 
 int
@@ -125,6 +125,13 @@ fixfault(Segment *s, ulong addr, int read, int doputmmu)
 			ref = lkp->ref;
 		if(ref > 1) {
 			unlock(lkp);
+
+			if(swapfull()){
+				qunlock(&s->lk);
+				pprint("swap space full\n");
+				faulterror(Enoswap, 1);
+			}
+
 			new = newpage(0, &s, addr);
 			if(s == 0)
 				return -1;
@@ -134,7 +141,7 @@ fixfault(Segment *s, ulong addr, int read, int doputmmu)
 		}
 		else {
 			/* save a copy of the original for the image cache */
-			if(lkp->image)
+			if(lkp->image && !swapfull())
 				duppage(lkp);
 
 			unlock(lkp);
@@ -214,7 +221,7 @@ retry:
 				continue;
 			kunmap(k);
 			putpage(new);
-			faulterror("sys: demand load I/O error");
+			faulterror("sys: demand load I/O error", 0);
 		}
 
 		ask = s->flen-soff;
@@ -223,7 +230,7 @@ retry:
 
 		n = devtab[c->type]->read(c, kaddr, ask, daddr);
 		if(n != ask)
-			faulterror(Eioload);
+			faulterror(Eioload, 0);
 		if(ask < BY2PG)
 			memset(kaddr+ask, 0, BY2PG-ask);
 
@@ -250,12 +257,12 @@ retry:
 			putpage(new);
 			qlock(&s->lk);
 			qunlock(&s->lk);
-			faulterror("sys: page in I/O error");
+			faulterror("sys: page in I/O error", 0);
 		}
 
 		n = devtab[c->type]->read(c, kaddr, BY2PG, daddr);
 		if(n != BY2PG)
-			faulterror(Eioload);
+			faulterror(Eioload, 0);
 
 		poperror();
 		kunmap(k);
diff --git a/port/portfns.h b/port/portfns.h
index 8de2eeb0bf5560b13530e7881425f03debf1ff55..b700fe2098f7369c8c027e1a8ae91947054ec4ef 100644
--- a/port/portfns.h
+++ b/port/portfns.h
@@ -295,6 +295,7 @@ void		splx(int);
 void		splxpc(int);
 void		srvrecover(Chan*, Chan*);
 int		swapcount(ulong);
+int		swapfull(void);
 void		swapinit(void);
 Block*		trimblock(Block*, int, int);
 void		tsleep(Rendez*, int (*)(void*), void*, int);
diff --git a/port/segment.c b/port/segment.c
index a6a65178290177b0eddce50019d5b7f67c48c168..66ef6bce2870c9ebc604c2bebe30281723990355 100644
--- a/port/segment.c
+++ b/port/segment.c
@@ -53,6 +53,9 @@ newseg(int type, ulong base, ulong size)
 	if(size > (SEGMAPSIZE*PTEPERTAB))
 		error(Enovmem);
 
+	if(swapfull())
+		error(Enoswap);
+
 	s = smalloc(sizeof(Segment));
 	s->ref = 1;
 	s->type = type;
@@ -157,7 +160,12 @@ dupseg(Segment **seg, int segno, int share)
 
 	case SG_STACK:
 		qlock(&s->lk);
+		if(waserror()){
+			qunlock(&s->lk);
+			nexterror();
+		}
 		n = newseg(s->type, s->base, s->size);
+		poperror();
 		break;
 
 	case SG_BSS:		/* Just copy on write */
@@ -169,7 +177,12 @@ dupseg(Segment **seg, int segno, int share)
 			qunlock(&s->lk);
 			return s;
 		}
+		if(waserror()){
+			qunlock(&s->lk);
+			nexterror();
+		}
 		n = newseg(s->type, s->base, s->size);
+		poperror();
 		break;
 
 	case SG_DATA:		/* Copy on write plus demand load info */
@@ -183,7 +196,12 @@ dupseg(Segment **seg, int segno, int share)
 			qunlock(&s->lk);
 			return s;
 		}
+		if(waserror()){
+			qunlock(&s->lk);
+			nexterror();
+		}
 		n = newseg(s->type, s->base, s->size);
+		poperror();
 
 		incref(s->image);
 		n->image = s->image;
@@ -438,6 +456,11 @@ ibrk(ulong addr, int seg)
 		return 0;
 	}
 
+	if(swapfull()){
+		qunlock(&s->lk);
+		error(Enoswap);
+	}
+
 	for(i = 0; i < NSEG; i++) {
 		ns = up->seg[i];
 		if(ns == 0 || ns == s)
diff --git a/port/swap.c b/port/swap.c
index 6ee65b0d1e0db595002d60eee5bcb64e82445e15..81f5a13f36b539c7e681f6b62f388ce50a9800b7 100644
--- a/port/swap.c
+++ b/port/swap.c
@@ -38,8 +38,11 @@ newswap(void)
 	uchar *look;
 
 	lock(&swapalloc);
-	if(swapalloc.free == 0)
-		panic("out of swap space");
+
+	if(swapalloc.free == 0){
+		unlock(&swapalloc);
+		return ~0;
+	}
 
 	look = memchr(swapalloc.last, 0, swapalloc.top-swapalloc.last);
 	if(look == 0)
@@ -285,6 +288,8 @@ pagepte(int type, Page **pg)
 		 *  referring to it from the cache
 		 */
 		daddr = newswap();
+		if(daddr == ~0)
+			break;
 		cachedel(&swapimage, daddr);
 
 		lock(outp);
@@ -396,3 +401,9 @@ setswapchan(Chan *c)
 
 	swapimage.c = c;
 }
+
+int
+swapfull(void)
+{
+	return swapalloc.free < conf.nswap/10;
+}