Limited graft traversal scope to lfs3_alloc

This drops the LFS3_TSTATE_GRAFT state for just explicitly iterating
over graft state in lfs3_alloc. This is cheaper as long as lfs3_alloc is
the only traversal we trigger while grafting.

We already rely on the lfs3_alloc-specific behavior of never touching
cksize/cksum fields anyways.

Note both lfs3_alloc_markinuse and lfs3_alloc_markinuse_ already have
multiple call sites and can't be inlined due to lookahead population in
lfs3_mtree_gc. We also don't need to worry about graft state there as
incremental traversals only make progress when bshrubs are at rest.

Saves a bit of code:

                 code          stack          ctx
  before:       38092           2456          656
  after:        38060 (-0.1%)   2456 (+0.0%)  656 (+0.0%)

  before graft: 37936           2456          636
  after graft:  38060 (+0.3%)   2456 (+0.0%)  656 (+3.1%)

Actually, surprisingly little code, but anything that simplifies
lfs3_mtree_traverse_ is welcome.

lfs3.c

@@ -9722,9 +9722,8 @@ enum {
     LFS3_TSTATE_BTREE       = 5,
     LFS3_TSTATE_OMDIRS      = 6,
     LFS3_TSTATE_OBTREE      = 7,
-    LFS3_TSTATE_GRAFT       = 8,
     #endif
-    LFS3_TSTATE_DONE        = 9,
+    LFS3_TSTATE_DONE        = 8,
 };
 
 static void lfs3_traversal_init(lfs3_traversal_t *t, uint32_t flags) {
@@ -9744,9 +9743,6 @@ static void lfs3_traversal_init(lfs3_traversal_t *t, uint32_t flags) {
     t->gcksum = 0;
 }
 
-// needed in lfs3_mtree_traverse_
-static inline lfs3_size_t lfs3_graft_count(lfs3_size_t graft_count);
-
 // low-level traversal _only_ finds blocks
 static int lfs3_mtree_traverse_(lfs3_t *lfs3, lfs3_traversal_t *t,
         lfs3_tag_t *tag_, lfs3_bptr_t *bptr) {
@@ -9861,10 +9857,9 @@ static int lfs3_mtree_traverse_(lfs3_t *lfs3, lfs3_traversal_t *t,
             err = lfs3_mtree_lookup(lfs3, t->b.o.mdir.mid,
                     &t->b.o.mdir);
             if (err) {
-                // end of mtree? all that's left is any graft state
+                // end of mtree? guess we're done
                 if (err == LFS3_ERR_NOENT) {
-                    t->u.gt = 0;
+                    lfs3_t_settstate(&t->b.o.flags, LFS3_TSTATE_DONE);
-                    lfs3_t_settstate(&t->b.o.flags, LFS3_TSTATE_GRAFT);
                     continue;
                 }
                 return err;
@@ -10030,21 +10025,6 @@ static int lfs3_mtree_traverse_(lfs3_t *lfs3, lfs3_traversal_t *t,
             continue;
         #endif
 
-        // traverse through in-flight grafts
-        case LFS3_TSTATE_GRAFT:;
-            // done?
-            if (t->u.gt >= lfs3_graft_count(lfs3->graft_count)) {
-                lfs3_t_settstate(&t->b.o.flags, LFS3_TSTATE_DONE);
-                continue;
-            }
-
-            if (tag_) {
-                *tag_ = LFS3_TAG_DATA;
-            }
-            bptr->data = lfs3->graft[t->u.gt];
-            t->u.gt += 1;
-            return 0;
-
         case LFS3_TSTATE_DONE:;
             return LFS3_ERR_NOENT;
 
@@ -10382,8 +10362,7 @@ static void lfs3_alloc_markinuse(lfs3_t *lfs3,
         lfs3_rbyd_t *rbyd = (lfs3_rbyd_t*)bptr->data.u.buffer;
         lfs3_alloc_markinuse_(lfs3, rbyd->blocks[0]);
 
-    } else if (tag == LFS3_TAG_BLOCK
+    } else if (tag == LFS3_TAG_BLOCK) {
-            || tag == LFS3_TAG_DATA) {
         lfs3_alloc_markinuse_(lfs3, lfs3_bptr_block(bptr));
 
     } else {
@@ -10458,6 +10437,9 @@ static lfs3_sblock_t lfs3_alloc_findfree(lfs3_t *lfs3) {
 }
 #endif
 
+// needed in lfs3_mtree_traverse_
+static inline lfs3_size_t lfs3_graft_count(lfs3_size_t graft_count);
+
 #if !defined(LFS3_RDONLY) && !defined(LFS3_2BONLY)
 static lfs3_sblock_t lfs3_alloc(lfs3_t *lfs3, bool erase) {
     while (true) {
@@ -10539,6 +10521,13 @@ static lfs3_sblock_t lfs3_alloc(lfs3_t *lfs3, bool erase) {
             lfs3_alloc_markinuse(lfs3, tag, &bptr);
         }
 
+        // mask out any in-flight graft state
+        for (lfs3_size_t i = 0;
+                i < lfs3_graft_count(lfs3->graft_count);
+                i++) {
+            lfs3_alloc_markinuse_(lfs3, lfs3->graft[i].u.disk.block);
+        }
+
         // mark anything not seen as free
         lfs3_alloc_markfree(lfs3);
     }