Try to read the silo signature to find the correct address to map

the silo into VM.  If this fails or we get garbage, the silo will
be cleared.

Fixes	#962

bin/varnishd/storage_persistent_mgt.c

@@ -120,6 +120,8 @@ void
 smp_mgt_init(struct stevedore *parent, int ac, char * const *av)
 {
 	struct smp_sc		*sc;
+	struct smp_sign		sgn;
+	void *target;
 	int i;
 
 	ASSERT_MGT();
@@ -158,7 +160,15 @@ smp_mgt_init(struct stevedore *parent, int ac, char * const *av)
 
 	AZ(ftruncate(sc->fd, sc->mediasize));
 
-	sc->base = mmap(NULL, sc->mediasize, PROT_READ|PROT_WRITE,
+	/* Try to determine correct mmap address */
+	i = read(sc->fd, &sgn, sizeof sgn);
+	assert(i == sizeof sgn);
+	if (!strcmp(sgn.ident, "SILO"))
+		target = (void*)sgn.mapped;
+	else
+		target = NULL;
+
+	sc->base = mmap(target, sc->mediasize, PROT_READ|PROT_WRITE,
 	    MAP_NOCORE | MAP_NOSYNC | MAP_SHARED, sc->fd, 0);
 
 	if (sc->base == MAP_FAILED)
@@ -169,8 +179,11 @@ smp_mgt_init(struct stevedore *parent, int ac, char * const *av)
 	sc->ident = SIGN_DATA(&sc->idn);
 
 	i = smp_valid_silo(sc);
-	if (i)
+	if (i) {
+		printf("Warning SILO (%s) not reloaded (reason=%d)\n",
+		    sc->filename, i);
 		smp_newsilo(sc);
+	}
 	AZ(smp_valid_silo(sc));
 
 	smp_metrics(sc);

bin/varnishd/storage_persistent_subr.c

@@ -238,26 +238,27 @@ smp_valid_silo(struct smp_sc *sc)
 
 	assert(strlen(SMP_IDENT_STRING) < sizeof si->ident);
 
-	if (smp_chk_sign(&sc->idn))
-		return (1);
+	i = smp_chk_sign(&sc->idn);
+	if (i)
+		return (i);
 
 	si = sc->ident;
 	if (strcmp(si->ident, SMP_IDENT_STRING))
-		return (2);
+		return (12);
 	if (si->byte_order != 0x12345678)
-		return (3);
+		return (13);
 	if (si->size != sizeof *si)
-		return (4);
+		return (14);
 	if (si->major_version != 2)
-		return (5);
+		return (15);
 	if (si->mediasize != sc->mediasize)
-		return (7);
+		return (17);
 	if (si->granularity != sc->granularity)
-		return (8);
+		return (18);
 	if (si->align < sizeof(void*))
-		return (9);
+		return (19);
 	if (!PWR2(si->align))
-		return (10);
+		return (20);
 	sc->align = si->align;
 	sc->unique = si->unique;
 

bin/varnishtest/tests/r00962.vtc

+varnishtest "Test address remapping"
+
+server s1 {
+	rxreq 
+	txresp 
+} -start
+
+shell "rm -f ${tmpdir}/_.per?"
+
+varnish v1 \
+	-arg "-pdiag_bitmap=0x20000" \
+	-storage "-spersistent,${tmpdir}/_.per1,10m -spersistent,${tmpdir}/_.per2,10m" \
+	-vcl+backend { 
+	sub vcl_fetch {
+		set beresp.storage = "s0";
+	}
+} -start 
+
+varnish v1 -stop
+
+varnish v1 -start
+
+client c1 {
+	txreq -url "/"
+	rxresp
+	expect resp.status == 200
+	expect resp.http.X-Varnish == "1001"
+} -run
+
+varnish v1 -cliok "storage.list"
+varnish v1 -cliok "debug.persistent s0 dump"
+varnish v1 -cliok "debug.persistent s0 sync"
+varnish v1 -stop
+
+varnish v2 \
+	-arg "-pdiag_bitmap=0x20000" \
+	-storage "-spersistent,${tmpdir}/_.per2,10m -spersistent,${tmpdir}/_.per1,10m" \
+	-vcl+backend { } -start 
+
+client c1 -connect ${v2_sock} {
+	txreq -url "/"
+	rxresp
+	expect resp.status == 200
+	expect resp.http.X-Varnish == "1001"
+} -run
+
+# shell "rm -f /tmp/__v1/_.per"