From f7165f3176aecd1b789e6464abd0607edaabc38e Mon Sep 17 00:00:00 2001
From: Christopher Haster <geky@geky.net>
Date: Fri, 7 Jun 2024 00:44:32 -0500
Subject: [PATCH] Tweaked SHRUBCOMMIT to infer alloc from block address

Turns out we don't need SHRUBALLOC, as we can infer if we need to reset
the shrub based on if it already exists in our mdir. Not in mdir =>
needs to alloc/reset.

This saves an internal tag and a bit of code:

           code          stack
  before: 33770           2600 (+0.0%)
  after:  33746 (-0.1%)   2600 (+0.0%)
---
 lfs.c | 36 +++++++++++++++---------------------
 1 file changed, 15 insertions(+), 21 deletions(-)

diff --git a/lfs.c b/lfs.c
index 4de2a901..a1310032 100644
--- a/lfs.c
+++ b/lfs.c
@@ -836,9 +836,8 @@ enum lfsr_tag {
     // in-device only tags, these should never get written to disk
     LFSR_TAG_INTERNAL       = 0x0800,
     LFSR_TAG_MOVE           = 0x0800,
-    LFSR_TAG_SHRUBALLOC     = 0x0801,
-    LFSR_TAG_SHRUBCOMMIT    = 0x0802,
-    LFSR_TAG_SHRUBTRUNK     = 0x0803,
+    LFSR_TAG_SHRUBCOMMIT    = 0x0801,
+    LFSR_TAG_SHRUBTRUNK     = 0x0802,
 
     // some in-device only tag modifiers
     LFSR_TAG_RM             = 0x8000,
@@ -6146,7 +6145,7 @@ static int lfsr_mdir_commit__(lfs_t *lfs, lfsr_mdir_t *mdir,
                             return err;
                         }
 
-                        // compact our bshrub
+                        // compact our shrub
                         err = lfsr_shrub_compact(lfs, &rbyd_, &shrub,
                                 &shrub);
                         if (err) {
@@ -6224,24 +6223,21 @@ static int lfsr_mdir_commit__(lfs_t *lfs, lfsr_mdir_t *mdir,
 
             // shrub tags append a set of attributes to an unrelated trunk
             // in our rbyd
-            } else if (attrs[i].tag == LFSR_TAG_SHRUBALLOC
-                    || attrs[i].tag == LFSR_TAG_SHRUBCOMMIT) {
-                const lfsr_shrubcommit_t *bshrubcommit = attrs[i].cat;
+            } else if (attrs[i].tag == LFSR_TAG_SHRUBCOMMIT) {
+                const lfsr_shrubcommit_t *shrubcommit = attrs[i].cat;
 
-                // SHRUBALLOC is roughly the same as SHRUBCOMMIT but also
-                // resets the shrub, we need to do this here so bshrub root
-                // extensions are atomic
-                if (attrs[i].tag == LFSR_TAG_SHRUBALLOC) {
-                    bshrubcommit->shrub->blocks[0] = rbyd_.blocks[0];
-                    bshrubcommit->shrub->trunk = LFSR_RBYD_ISSHRUB | 0;
-                    bshrubcommit->shrub->weight = 0;
+                // reset shrub if it doesn't live in our block, this happens
+                // when converting from a btree
+                if (shrubcommit->shrub->blocks[0] != rbyd_.blocks[0]) {
+                    shrubcommit->shrub->blocks[0] = rbyd_.blocks[0];
+                    shrubcommit->shrub->trunk = LFSR_RBYD_ISSHRUB | 0;
+                    shrubcommit->shrub->weight = 0;
                 }
 
+                // commit to shrub
                 int err = lfsr_shrub_commit(lfs, &rbyd_,
-                        bshrubcommit->shrub,
-                        bshrubcommit->rid,
-                        bshrubcommit->attrs,
-                        bshrubcommit->attr_count);
+                        shrubcommit->shrub, shrubcommit->rid,
+                        shrubcommit->attrs, shrubcommit->attr_count);
                 if (err) {
                     return err;
                 }
@@ -10559,9 +10555,7 @@ static int lfsr_bshrub_commit(lfs_t *lfs, lfsr_file_t *file,
         // commit to shrub
         int err = lfsr_mdir_commit(lfs, &file->o.mdir, LFSR_ATTRS(
                 LFSR_ATTR_SHRUBCOMMIT(
-                    (alloc)
-                        ? LFSR_TAG_SHRUBALLOC
-                        : LFSR_TAG_SHRUBCOMMIT, 0,
+                    LFSR_TAG_SHRUBCOMMIT, 0,
                     &file->bshrub_.u.bshrub, bid,
                     attrs, attr_count)));
         if (err) {