[3.0] 5626096 The law of unconsidered consequences strikes again:

[Tollef Fog Heen]

commit 5626096010669ede48b9dd4241651e0655c8e797
Author: Poul-Henning Kamp <phk at FreeBSD.org>
Date:   Mon Aug 22 08:21:51 2011 +0000

    The law of unconsidered consequences strikes again:
    
    When we pushed the object allocation into the stevedores for
    -spersistent, we did not add LRU eviction to that allocation
    path.
    
    Then we added the Transient storage as a fallback for objects
    we could not allocate, and they all went there.
    
    Change the way object allocation works as follows:
    
            If VCL set a stevedore hint and it is valid, we stick
            with it, and LRU that stevedore attempting to make space.
    
            If no valid hint is given, try all stevedores in turn,
            then LRU one of them to make space.
    
    Fixes	#953

diff --git a/bin/varnishd/stevedore.c b/bin/varnishd/stevedore.c
index 1dad892..624d2b1 100644
--- a/bin/varnishd/stevedore.c
+++ b/bin/varnishd/stevedore.c
@@ -123,17 +123,22 @@ LRU_Free(struct lru *lru)
  */
 
 static struct stevedore *
-stv_pick_stevedore(const char *hint)
+stv_pick_stevedore(const struct sess *sp, const char **hint)
 {
 	struct stevedore *stv;
 
-	if (hint != NULL && *hint != '\0') {
+	AN(hint);
+	if (*hint != NULL && **hint != '\0') {
 		VTAILQ_FOREACH(stv, &stevedores, list) {
-			if (!strcmp(stv->ident, hint))
+			if (!strcmp(stv->ident, *hint))
 				return (stv);
 		}
-		if (!strcmp(TRANSIENT_STORAGE, hint))
+		if (!strcmp(TRANSIENT_STORAGE, *hint))
 			return (stv_transient);
+
+		/* Hint was not valid, nuke it */
+		WSP(sp, SLT_Debug, "Storage hint not usable");
+		*hint = NULL;
 	}
 	/* pick a stevedore and bump the head along */
 	stv = VTAILQ_NEXT(stv_next, list);
@@ -182,7 +187,7 @@ stv_alloc(const struct sess *sp, size_t size)
 			break;
 
 		/* Enough is enough: try another if we have one */
-		if (++fail == 50)	/* XXX Param */
+		if (++fail >= params->nuke_limit)
 			break;
 	}
 	if (st != NULL)
@@ -297,9 +302,10 @@ STV_NewObject(struct sess *sp, const char *hint, unsigned wsl, struct exp *ep,
     uint16_t nhttp)
 {
 	struct object *o;
-	struct stevedore *stv;
+	struct stevedore *stv, *stv0;
 	unsigned lhttp, ltot;
 	struct stv_objsecrets soc;
+	int i;
 
 	assert(wsl > 0);
 	wsl = PRNDUP(wsl);
@@ -316,9 +322,25 @@ STV_NewObject(struct sess *sp, const char *hint, unsigned wsl, struct exp *ep,
 
 	ltot = sizeof *o + wsl + lhttp;
 
-	stv = stv_pick_stevedore(hint);
+	stv = stv0 = stv_pick_stevedore(sp, &hint);
 	AN(stv->allocobj);
 	o = stv->allocobj(stv, sp, ltot, &soc);
+	if (o == NULL && hint == NULL) {
+		do {
+			stv = stv_pick_stevedore(sp, &hint);
+			AN(stv->allocobj);
+			o = stv->allocobj(stv, sp, ltot, &soc);
+		} while (o == NULL && stv != stv0);
+	}
+	if (o == NULL) {
+		/* no luck; try to free some space and keep trying */
+		for (i = 0; o == NULL && i < params->nuke_limit; i++) {
+			if (EXP_NukeOne(sp, stv->lru) == -1)
+				break;
+			o = stv->allocobj(stv, sp, ltot, &soc);
+		}
+	}
+
 	if (o == NULL)
 		return (NULL);
 	CHECK_OBJ_NOTNULL(o, OBJECT_MAGIC);