[master] 1970515d8 cache_fetch: make max_retries consistent during the busyobj lifetime

[Nils Goroll]

commit 1970515d8a4ae770cb610c98a155d456fe4e42e9
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Sun Feb 9 19:35:09 2025 +0100

    cache_fetch: make max_retries consistent during the busyobj lifetime
    
    There is no assertion to be hit like in the previous commit, but we might still
    want to avoid running in a situation where the number of retries "suddenly"
    changes. For example, we could fail for "too many retries", end up in v_b_e {}
    and be able to retry from there, if the cache parameter was changed at just the
    right time.

diff --git a/bin/varnishd/cache/cache.h b/bin/varnishd/cache/cache.h
index 1be031eb8..ffa3d8577 100644
--- a/bin/varnishd/cache/cache.h
+++ b/bin/varnishd/cache/cache.h
@@ -383,6 +383,7 @@ struct busyobj {
 
 	char			*end;
 
+	unsigned		max_retries;
 	unsigned		retries;
 	struct req		*req;
 	struct sess		*sp;
diff --git a/bin/varnishd/cache/cache_busyobj.c b/bin/varnishd/cache/cache_busyobj.c
index 5293186fe..42332ecd7 100644
--- a/bin/varnishd/cache/cache_busyobj.c
+++ b/bin/varnishd/cache/cache_busyobj.c
@@ -72,6 +72,7 @@ VBO_GetBusyObj(const struct worker *wrk, const struct req *req)
 	XXXAN(bo);
 	bo->magic = BUSYOBJ_MAGIC;
 	bo->end = (char *)bo + sz;
+	bo->max_retries = cache_param->max_retries;
 
 	p = (void*)(bo + 1);
 	p = (void*)PRNDUP(p);
diff --git a/bin/varnishd/cache/cache_fetch.c b/bin/varnishd/cache/cache_fetch.c
index dc842208b..196817512 100644
--- a/bin/varnishd/cache/cache_fetch.c
+++ b/bin/varnishd/cache/cache_fetch.c
@@ -530,7 +530,7 @@ vbf_stp_startfetch(struct worker *wrk, struct busyobj *bo)
 			bo->htc->doclose = SC_RESP_CLOSE;
 		vbf_cleanup(bo);
 
-		if (bo->retries++ < cache_param->max_retries)
+		if (bo->retries++ < bo->max_retries)
 			return (F_STP_RETRY);
 
 		VSLb(bo->vsl, SLT_VCL_Error,
@@ -995,7 +995,7 @@ vbf_stp_error(struct worker *wrk, struct busyobj *bo)
 
 	if (wrk->vpi->handling == VCL_RET_RETRY) {
 		VSB_destroy(&synth_body);
-		if (bo->retries++ < cache_param->max_retries)
+		if (bo->retries++ < bo->max_retries)
 			return (F_STP_RETRY);
 		VSLb(bo->vsl, SLT_VCL_Error, "Too many retries, failing");
 		return (F_STP_FAIL);