From 9ceaca372af345801844ec92194894d4478ea0f3 Mon Sep 17 00:00:00 2001
From: Christopher Haster <geky@geky.net>
Date: Tue, 21 Mar 2023 14:01:33 -0500
Subject: [PATCH] In B-tree commit, moved pending attrs before merge attempts

I'm still not sure this is the right place for this, but it does
simplify pending attr calculations during merge and deduplicates
two instances of writing pending attrs, at the cost of needing to
track an additional rbyd weight during merge.

Going to roll with this for now, the B-tree merge code needs to be
cleaned up anyways, maybe it's possible to simplify the state we need to
track.

Another side-effect is this makes our B-trees slightly less aggressive
at merging. I have no idea if this is a good or bad thing.
---
 lfs.c | 36 +++++++++++++++++-------------------
 1 file changed, 17 insertions(+), 19 deletions(-)

diff --git a/lfs.c b/lfs.c
index 0b371fad..57ff12ea 100644
--- a/lfs.c
+++ b/lfs.c
@@ -3081,6 +3081,16 @@ static int lfsr_btree_commit(lfs_t *lfs,
             }
         }
 
+        // append any pending attrs, it's up to upper
+        // layers to make sure these always fit
+        for (const struct lfsr_attr *attr = attrs; attr; attr = attr->next) {
+            err = lfsr_rbyd_append(lfs, &rbyd_,
+                    attr->tag, attr->id, attr->data);
+            if (err) {
+                return err;
+            }
+        }
+
         // is our compacted size too small? try to merge with one of
         // our siblings
         if (rbyd_.off < lfs->cfg->block_size/4
@@ -3092,9 +3102,8 @@ static int lfsr_btree_commit(lfs_t *lfs,
         merge_abort:;
         }
 
-        // finalize commit with new attrs, it's up to upper
-        // layers to make sure these always fit
-        err = lfsr_rbyd_commit(lfs, &rbyd_, attrs);
+        // finalize commit
+        err = lfsr_rbyd_commit(lfs, &rbyd_, NULL);
         if (err) {
             return err;
         }
@@ -3383,7 +3392,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
         // not last child? try the right sibling
         } else {
             sid = rid+1;
-            sdelta = rweight;
+            sdelta = rbyd_.weight;
         }
 
         // try looking up the sibling
@@ -3434,6 +3443,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
         }
 
         // try to add our sibling's tags to our rbyd
+        lfs_size_t rweight_ = rbyd_.weight;
         tag = 0;
         id = 0;
         while (true) {
@@ -3474,7 +3484,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
                         LFSR_TAG_SHRINK,
                         sdelta,
                         // TODO also this is a weird way to use lfsr_data_t
-                        LFSR_DATA_BUF(NULL, rbyd_.weight - rweight));
+                        LFSR_DATA_BUF(NULL, rbyd_.weight - rweight_));
                 if (err) {
                     return err;
                 }
@@ -3484,7 +3494,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
         }
 
         // bring in name that previously split the siblings
-        lfsr_tag_t  split_tag;
+        lfsr_tag_t split_tag;
         lfs_off_t split_off;
         lfs_size_t split_size;
         err = lfsr_rbyd_lookup(lfs, &parent,
@@ -3499,7 +3509,7 @@ static int lfsr_btree_commit(lfs_t *lfs,
             // lookup the id of the previously-split entry
             lfs_ssize_t split_id;
             err = lfsr_rbyd_lookup(lfs, &rbyd_,
-                    LFSR_TAG_MK, (sdelta == 0 ? sweight : rweight),
+                    LFSR_TAG_MK, (sdelta == 0 ? sweight : rweight_),
                     NULL, &split_id, NULL, NULL, NULL);
             if (err) {
                 return err;
@@ -3513,18 +3523,6 @@ static int lfsr_btree_commit(lfs_t *lfs,
             }
         }
 
-        // finalize commit with new attrs, it's up to upper
-        // layers to make sure these always fit
-        for (const struct lfsr_attr *attr = attrs; attr; attr = attr->next) {
-            err = lfsr_rbyd_append(lfs, &rbyd_,
-                    // TODO can this be expressed better?
-                    attr->tag, attr->id + (sdelta == 0 ? sweight : 0),
-                    attr->data);
-            if (err) {
-                return err;
-            }
-        }
-
         err = lfsr_rbyd_commit(lfs, &rbyd_, NULL);
         if (err) {
             return err;