From e6f28e202e45225d081242a833d2b3949b7e3b12 Mon Sep 17 00:00:00 2001
From: Christopher Haster <geky@geky.net>
Date: Tue, 29 Apr 2025 00:01:32 -0500
Subject: [PATCH] Recycle mdir rbyd in mtree lookups

A bit of a hack, but this saves some stack:

           code          stack          ctx
  before: 35764           2392          640
  after:  35768 (+0.0%)   2368 (-1.0%)  640 (+0.0%)

It's not like the rbyd is doing anything else until we fetch the mdir.
---
 lfs.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/lfs.c b/lfs.c
index 51fdc8a8..857bd147 100644
--- a/lfs.c
+++ b/lfs.c
@@ -7678,13 +7678,12 @@ static int lfsr_mtree_lookup(lfs_t *lfs, lfsr_smid_t mid,
     // look up mdir in actual mtree
     } else {
         lfsr_bid_t bid;
-        lfsr_rbyd_t rbyd;
         lfsr_srid_t rid;
         lfsr_tag_t tag;
         lfsr_bid_t weight;
         lfsr_data_t data;
         int err = lfsr_btree_lookupleaf(lfs, &lfs->mtree, mid,
-                &bid, &rbyd, &rid, &tag, &weight, &data);
+                &bid, &mdir->rbyd, &rid, &tag, &weight, &data);
         if (err) {
             LFS_ASSERT(err != LFS_ERR_NOENT);
             return err;
@@ -7696,7 +7695,7 @@ static int lfsr_mtree_lookup(lfs_t *lfs, lfsr_smid_t mid,
 
         // if we found an mname, lookup the mdir
         if (tag == LFSR_TAG_MNAME) {
-            err = lfsr_rbyd_lookup(lfs, &rbyd, rid, LFSR_TAG_MDIR,
+            err = lfsr_rbyd_lookup(lfs, &mdir->rbyd, rid, LFSR_TAG_MDIR,
                     NULL, &data);
             if (err) {
                 LFS_ASSERT(err != LFS_ERR_NOENT);
@@ -9172,14 +9171,13 @@ static int lfsr_mtree_namelookup(lfs_t *lfs,
     // lookup name in actual mtree
     } else {
         lfsr_bid_t bid;
-        lfsr_rbyd_t rbyd;
         lfsr_srid_t rid;
         lfsr_tag_t tag;
         lfsr_bid_t weight;
         lfsr_data_t data;
         lfs_scmp_t cmp = lfsr_btree_namelookupleaf(lfs, &lfs->mtree,
                 did, name, name_len,
-                &bid, &rbyd, &rid, &tag, &weight, &data);
+                &bid, &mdir->rbyd, &rid, &tag, &weight, &data);
         if (cmp < 0) {
             LFS_ASSERT(cmp != LFS_ERR_NOENT);
             return cmp;
@@ -9190,7 +9188,7 @@ static int lfsr_mtree_namelookup(lfs_t *lfs,
 
         // if we found an mname, lookup the mdir
         if (tag == LFSR_TAG_MNAME) {
-            int err = lfsr_rbyd_lookup(lfs, &rbyd, rid, LFSR_TAG_MDIR,
+            int err = lfsr_rbyd_lookup(lfs, &mdir->rbyd, rid, LFSR_TAG_MDIR,
                     NULL, &data);
             if (err) {
                 LFS_ASSERT(err != LFS_ERR_NOENT);