Have descend return the radix level we stopped at

Rather awkward API, but it's enough to implement skipping of empty nodes.

Have descend return the radix level we stopped at
2ca11e63 · David Benjamin · e10e8bda · 2ca11e63
--- a/kernel/radix.cc
+++ b/kernel/radix.cc
@@ -5,8 +5,9 @@
 #include "cpputil.hh"
 #include "radix.hh"

+// Returns the level we stopped at.
 template<class CB>
-void
+u32
 descend(u64 key, markptr<void> *n, u32 level, CB cb, bool create)
 {
  static_assert(key_bits == bits_per_level * radix_levels,
@@ -14,26 +15,29 @@ descend(u64 key, markptr<void> *n, u32 level, CB cb, bool create)
  assert(n);

  void *v = n->ptr();
-  if (v == 0) {
-    // Node isn't there. Just return.
-    if (!create)
-      return;
+  if (v == 0 && create) {
    radix_node *new_rn = new radix_node();
    if (n->ptr().cmpxch_update(&v, (void*) new_rn))
      v = new_rn;
    else
      delete new_rn;
  }
+  // Node isn't there. Just return.
+  if (v == 0) {
+    return level+1;
+  }

  radix_node *rn = (radix_node*) v;

  u64 idx = key >> (bits_per_level * level);
  idx &= (1<<bits_per_level)-1;
  markptr<void> *vptr = &rn->ptr[idx];
-  if (level == 0)
+  if (level == 0) {
    cb(vptr);
-  else
-    descend(key, vptr, level-1, cb, create);
+    return level;
+  } else {
+    return descend(key, vptr, level-1, cb, create);
+  }
 }

 radix_elem*
@@ -55,11 +59,14 @@ radix::search_lock(u64 start, u64 size)
 radix_range::radix_range(radix *r, u64 start, u64 size)
  : r_(r), start_(start), size_(size)
 {
-  for (u64 k = start_; k != start_ + size_; k++)
-    descend(k, &r_->root_, radix_levels-1, [](markptr<void> *v) {
-        while (!v->mark().xchg(true))
-          ; // spin
-      }, true);
+  for (u64 k = start_; k != start_ + size_; k++) {
+    if (descend(k, &r_->root_, radix_levels-1, [](markptr<void> *v) {
+          while (!v->mark().xchg(true))
+            ; // spin
+        }, true) != 0) {
+      panic("radix_range");
+    }
+  }
 }

 radix_range::~radix_range()
@@ -67,10 +74,13 @@ radix_range::~radix_range()
  if (!r_)
    return;

-  for (u64 k = start_; k != start_ + size_; k++)
-    descend(k, &r_->root_, radix_levels-1, [](markptr<void> *v) {
-        v->mark() = false;
-      }, true);
+  for (u64 k = start_; k != start_ + size_; k++) {
+    if (descend(k, &r_->root_, radix_levels-1, [](markptr<void> *v) {
+          v->mark() = false;
+        }, true) != 0) {
+      panic("~radix_range");
+    }
+  }
 }

 void
@@ -82,15 +92,18 @@ radix_range::replace(u64 start, u64 size, radix_elem *val)
  assert(start >= start_);
  assert(start + size <= start_ + size_);

-  for (u64 k = start; k != start + size; k++)
-    descend(k, &r_->root_, radix_levels-1, [val](markptr<void> *v) {
-        void* cur = v->ptr().load();
-        while (!v->ptr().cmpxch_update(&cur, val))
-          ; // spin
-        val->incref();
-        if (cur)
-          ((radix_elem*) cur)->decref();
-      }, true);
+  for (u64 k = start; k != start + size; k++) {
+    if (descend(k, &r_->root_, radix_levels-1, [val](markptr<void> *v) {
+          void* cur = v->ptr().load();
+          while (!v->ptr().cmpxch_update(&cur, val))
+            ; // spin
+          val->incref();
+          if (cur)
+            ((radix_elem*) cur)->decref();
+        }, true)) {
+      panic("radix_range::replace");
+    }
+  }
 }

 radix_elem*