t: Filled out rest of test_traversal

There can always be more tests, but I think these give a nice set of
coverage over corner-cases in our traversal clobbering scheme.

These did find a couple bugs:

- If we clobber an inlined mroot, we need to adjust the mid by two
  mdirs, but only if there is no mtree/mdirs.

  To avoid this and other mid-related headaches, we just provide the new
  mid in lfsr_mdir_commit, since we always know it here.

- lfsr_mdir_commit compares mdirs by mptr, which means we need to
  clobber traversal's mdir's mptrs or else lfsr_mdir_commit will clobber
  already-clobbered traversals.

  There may be a better way to solve this, but it will probably get into
  the weeds with how lfsr_mdir_commit relies on mids vs mptrs...

Code changes:

           code          stack
  before: 34570           2624
  after:  34566 (-0.0%)   2624 (+0.0%)

Now that the dust has settled and we sort of know what the traversal
implementation will look like, we can look at the before and after to
get a rough idea of how much the traversal API actually costs:

                          code          stack
  no-traversal (before): 33886           2560
  yes-traversal (after): 34566 (+2.0%)   2624 (+2.5%)

Note this still includes the annoying lfsr_btree_traverse inlining stack
cost, which isn't really the traversal API's fault and may be avoidable
in the future.

lfs.c

@@ -5216,7 +5216,8 @@ static bool lfsr_mid_isopen(lfs_t *lfs, lfsr_smid_t mid) {
 }
 
 // needed in lfsr_opened_clobber
-static void lfsr_traversal_clobberopen(lfs_t *lfs, lfsr_traversal_t *t);
+static void lfsr_traversal_clobber(lfs_t *lfs, lfsr_traversal_t *t,
+        lfsr_smid_t mid);
 
 // traversal invalidation things
 static void lfsr_opened_clobber(lfs_t *lfs, lfsr_omdir_t *o, bool dirty) {
@@ -5229,7 +5230,7 @@ static void lfsr_opened_clobber(lfs_t *lfs, lfsr_omdir_t *o, bool dirty) {
             // clobber any traversals referencing our mdir
             lfsr_traversal_t *t = (lfsr_traversal_t*)o_;
             if (t->mt.ot == o) {
-                lfsr_traversal_clobberopen(lfs, t);
+                lfsr_traversal_clobber(lfs, t, -1);
             }
         }
     }
@@ -6866,9 +6867,6 @@ static int lfsr_mroot_parent(lfs_t *lfs, const lfsr_mptr_t *mptr,
     }
 }
 
-// needed in lfsr_mdir_commit
-static void lfsr_traversal_clobbermdir(lfs_t *lfs, lfsr_traversal_t *t);
-
 // high-level mdir commit
 //
 // this is atomic and updates any opened mdirs, lfs_t, etc
@@ -7436,25 +7434,24 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
         }
     }
 
+    // clobber any related traversals
     for (lfsr_omdir_t *o = lfs->opened; o; o = o->next) {
         if (o->type == LFS_TYPE_TRAVERSAL) {
             // mark all traversals as dirty
             o->flags |= LFS_F_DIRTY;
 
-            // clobber any related traversals
+            // clobber any mdir related traversals
             if (lfsr_mdir_cmp(&o->mdir, mdir) == 0) {
-                lfsr_traversal_clobbermdir(lfs, (lfsr_traversal_t*)o);
-            }
-        }
+                lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o,
+                        lfsr_mid_bid(lfs, mdir->mid) + 1);
             }
 
-    // if mroot/mtree changed, clobber any related traversals
-    if (lfsr_mdir_cmp(&mroot_, &lfs->mroot) != 0
-            || lfsr_mtree_cmp(&mtree_, &lfs->mtree) != 0) {
-        for (lfsr_omdir_t *o = lfs->opened; o; o = o->next) {
-            if (o->type == LFS_TYPE_TRAVERSAL
+            // if mroot/mtree changed, clobber any mroot/mtree traversals
+            if ((lfsr_mdir_cmp(&mroot_, &lfs->mroot) != 0
+                        || lfsr_mtree_cmp(&mtree_, &lfs->mtree) != 0)
                     && o->mdir.mid == -1) {
-                lfsr_traversal_clobbermdir(lfs, (lfsr_traversal_t*)o);
+                lfsr_traversal_clobber(lfs, (lfsr_traversal_t*)o,
+                        0);
             }
         }
     }
@@ -7837,6 +7834,7 @@ enum {
         .o.state=LFSR_TSTATE_MROOTANCHOR, \
         .o.flags=_flags, \
         .o.mdir.mid=-1, \
+        .o.mdir.rbyd.blocks={0,0}, \
         .ot=NULL, \
         .u.mtortoise.mptr={{0, 0}}, \
         .u.mtortoise.step=0, \
@@ -7885,6 +7883,8 @@ static void lfsr_fs_traverserewind(lfs_t *lfs, lfsr_mtraversal_t *mt) {
     mt->o.flags &= ~LFS_F_DIRTY;
     mt->o.state = LFSR_TSTATE_MROOTANCHOR;
     mt->o.mdir.mid = -1;
+    mt->o.mdir.rbyd.blocks[0] = 0;
+    mt->o.mdir.rbyd.blocks[1] = 0;
     mt->ot = NULL;
     mt->u.mtortoise.mptr.blocks[0] = 0;
     mt->u.mtortoise.mptr.blocks[1] = 0;
@@ -7892,22 +7892,23 @@ static void lfsr_fs_traverserewind(lfs_t *lfs, lfsr_mtraversal_t *mt) {
     mt->u.mtortoise.power = 0;
 }
 
-static void lfsr_fs_traverseclobbermdir(lfs_t *lfs, lfsr_mtraversal_t *mt) {
+static void lfsr_fs_traverseclobber(lfs_t *lfs, lfsr_mtraversal_t *mt,
+        lfsr_smid_t mid) {
     (void)lfs;
+    if (mid != -1) {
         // increment the mid (to make progress) and reset to mdir iteration
         mt->o.state = LFSR_TSTATE_MDIRS;
-    mt->o.mdir.mid = lfsr_mid_bid(lfs, mt->o.mdir.mid)
-            + (1 << lfs->mdir_bits);
+        mt->o.mdir.mid = mid;
+        mt->o.mdir.rbyd.blocks[0] = 0;
+        mt->o.mdir.rbyd.blocks[1] = 0;
         mt->ot = NULL;
-}
-
-static void lfsr_fs_traverseclobberopen(lfs_t *lfs, lfsr_mtraversal_t *mt) {
-    (void)lfs;
+    } else {
         // move to next omdir
         LFS_ASSERT(mt->o.state == LFSR_TSTATE_OMDIRS
                 || mt->o.state == LFSR_TSTATE_OBTREE);
         mt->o.state = LFSR_TSTATE_OMDIRS;
         mt->ot = mt->ot->next;
+    }
 }
 
 
@@ -9420,18 +9421,10 @@ failed:;
 
 /// High-level filesystem traversal ///
 
-static void lfsr_traversal_clobbermdir(lfs_t *lfs, lfsr_traversal_t *t) {
+static void lfsr_traversal_clobber(lfs_t *lfs, lfsr_traversal_t *t,
+        lfsr_smid_t mid) {
     // clobber low-level traversal
-    lfsr_fs_traverseclobbermdir(lfs, &t->mt);
-
-    // and clear any pending blocks
-    t->blocks[0] = -1;
-    t->blocks[1] = -1;
-}
-
-static void lfsr_traversal_clobberopen(lfs_t *lfs, lfsr_traversal_t *t) {
-    // clobber low-level traversal
-    lfsr_fs_traverseclobberopen(lfs, &t->mt);
+    lfsr_fs_traverseclobber(lfs, &t->mt, mid);
 
     // and clear any pending blocks
     t->blocks[0] = -1;

tests/test_badblocks.toml

@@ -3,7 +3,8 @@ after = [
     'test_dirs',
     'test_files',
     'test_fwrite',
-    'test_forphans'
+    'test_forphans',
+    'test_traversal',
 ]
 
 

tests/test_powerloss.toml

@@ -8,6 +8,7 @@ after = [
     'test_dirs',
     'test_files',
     'test_forphans',
+    'test_traversal',
 ]