[master] c096659dd Fix surplus vcldir cleanup

[Nils Goroll]

commit c096659dd7b7932ead816d0389c9b24911e25dae
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Wed Jan 31 09:28:13 2024 +0100

    Fix surplus vcldir cleanup
    
    in VRT_AddDirector, we create the new vcldir with an initial
    reference, which we need to drop if we can not add it.
    
    Compare:
    
            VRT_AddDirector()
                    ...
                    vdir->refcnt++;
    
            vcldir_free()
                    ...
                    AZ(vdir->refcnt);
    
    Noticed when testing other experimental changes while working on
    https://github.com/nigoroll/libvmod-dynamic/issues/110
    
     #5  0x000055820c8cb845 in VAS_Fail (func=0x55820c904559 "vcldir_free", file=0x55820c903a47 "cache/cache_vrt_vcl.c",
         line=150, cond=0x55820c90459a "(vdir->refcnt) == 0", kind=VAS_ASSERT) at vas.c:67
     #6  0x000055820c83a442 in vcldir_free (vdir=0x7f662aa53140) at cache/cache_vrt_vcl.c:150
     #7  0x000055820c839fe1 in VRT_AddDirector (ctx=0x7f662befe250, m=0x55820c965260 <vbe_methods_noprobe>,
         priv=0x7f662aa20780, fmt=0x55820c900f7f "%s") at cache/cache_vrt_vcl.c:219
     #8  0x000055820c7c7c4d in VRT_new_backend_clustered (ctx=0x7f662befe250, vc=0x0, vrt=0x7f662befdd10, via=0x0)
        at cache/cache_backend.c:737
     #9  0x000055820c7c8632 in VRT_new_backend (ctx=0x7f662befe250, vrt=0x7f662befdd10, via=0x0)
         at cache/cache_backend.c:755

diff --git a/bin/varnishd/cache/cache_vrt_vcl.c b/bin/varnishd/cache/cache_vrt_vcl.c
index 85b594b7d..fb7043963 100644
--- a/bin/varnishd/cache/cache_vrt_vcl.c
+++ b/bin/varnishd/cache/cache_vrt_vcl.c
@@ -218,6 +218,8 @@ VRT_AddDirector(VRT_CTX, const struct vdi_methods *m, void *priv,
 	Lck_Unlock(&vcl_mtx);
 
 	if (temp == VCL_TEMP_COOLING) {
+		assert(vdir->refcnt == 1);
+		vdir->refcnt = 0;
 		vcldir_free(vdir);
 		return (NULL);
 	}