smgr: Make SMgrRelation initialization safer against errors

In case the smgr_open callback failed, the ->pincount field would not be
initialized and the relation would not be put onto the unpinned_relns list.

This buglet was introduced in 21d9c3ee4ef7, in 17.

Discussion: https://postgr.es/m/3vae7l5ozvqtxmd7rr7zaeq3qkuipz365u3rtim5t5wdkr6f4g@vkgf2fogjirl
Backpatch-through: 17

diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c
index ebe35c04de59c4507a34c51656b0459377be72be..e6cbb9b4ca22fc1cac3cc870a7d4017e84b92ea4 100644 (file)
--- a/src/backend/storage/smgr/smgr.c
+++ b/src/backend/storage/smgr/smgr.c
@@ -234,12 +234,12 @@ smgropen(RelFileLocator rlocator, ProcNumber backend)
            reln->smgr_cached_nblocks[i] = InvalidBlockNumber;
        reln->smgr_which = 0;   /* we only have md.c at present */
 
-       /* implementation-specific initialization */
-       smgrsw[reln->smgr_which].smgr_open(reln);
-
        /* it is not pinned yet */
        reln->pincount = 0;
        dlist_push_tail(&unpinned_relns, &reln->node);
+
+       /* implementation-specific initialization */
+       smgrsw[reln->smgr_which].smgr_open(reln);
    }
 
    return reln;