{t:4160] merging to mainline

git-svn-id: file:///svn/toku/tokudb@37230 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/brt.c

@@ -249,7 +249,7 @@ static void brtnode_put_cmd (
 
 
 static void
-flush_this_child (struct brt_header* h, BRTNODE node, BRTNODE child, int childnum);
+flush_this_child (struct brt_header* h, BRTNODE node, BRTNODE child, int childnum, bool started_at_root);
 
 static void brt_verify_flags(BRT brt, BRTNODE node) {
     assert(brt->flags == node->flags);
@@ -873,7 +873,33 @@ exit:
 }
 
 
-static void flush_some_child(struct brt_header* h, BRTNODE node, int *n_dirtied, int cascades, bool suppress_leaf_merge);
+// The parameter "started_at_root" is needed to resolve #4147 and #4160,
+// which are subtle interactions of background flushing (cleaner and
+// flusher threads) and MSN logic.
+//
+// When we rebalance basement nodes to write out a leaf, we can't have two
+// basement nodes with different max_msn_applieds.  When we flush to a
+// basement node, it may have stale ancestors' messages applied already.
+//
+// If we've flushed everything down from the root recursively, then there
+// is no problem.  Anything that was applied to the leaf node by a query
+// already must be in the batch of stuff we're flushing, so it's okay to
+// do whatever we want, the MSNs will be consistent.
+//
+// But if we started somewhere in the middle (as a cleaner thread does),
+// then we might not have all the messages that were applied to the leaf,
+// and some basement nodes may be in a different state than others.  So
+// before we flush to it, we have to destroy and re-read (off disk) the
+// basement nodes which have messages applied.  Similarly, if a flush
+// started in the middle wants to merge two leaf nodes, we can't do that
+// because we might create a leaf node in a bad state.
+//
+// We use "started_at_root" to decide what to do about this problem in
+// code further down.  For now, anything started by the cleaner thread
+// will have started_at_root==false and anything started by the flusher
+// thread will have started_at_root==true, but future mechanisms need to
+// be mindful of this issue.
+static void flush_some_child(struct brt_header* h, BRTNODE node, int *n_dirtied, int cascades, bool started_at_root);
 static void bring_node_fully_into_memory(BRTNODE node, struct brt_header *h);
 
 // TODO 3988 Leif set cleaner_nodes_dirtied
@@ -928,7 +954,7 @@ toku_brtnode_cleaner_callback(void *brtnode_pv, BLOCKNUM blocknum, u_int32_t ful
     // Either flush_some_child will unlock the node, or we do it here.
     if (toku_bnc_nbytesinbuf(BNC(node, childnum)) > 0) {
         int n_dirtied = 0;
-        flush_some_child(h, node, &n_dirtied, 0, true);
+        flush_some_child(h, node, &n_dirtied, 0, false);
         brt_status.cleaner_nodes_dirtied += n_dirtied;
     } else {
         toku_unpin_brtnode_off_client_thread(h, node);
@@ -1978,7 +2004,7 @@ static void call_flusher_thread_callback(int ft_state) {
 //  - possibly flush either new children created from split, otherwise unlock children
 //
 static void
-brt_split_child (struct brt_header* h, BRTNODE node, int childnum, BRTNODE child, bool suppress_leaf_merge)
+brt_split_child (struct brt_header* h, BRTNODE node, int childnum, BRTNODE child, bool started_at_root)
 {
     assert(node->height>0);
     assert(toku_bnc_nbytesinbuf(BNC(node, childnum))==0); // require that the buffer for this child is empty
@@ -2011,11 +2037,11 @@ brt_split_child (struct brt_header* h, BRTNODE node, int childnum, BRTNODE child
     toku_unpin_brtnode_off_client_thread(h, node);
     if (nodea->height > 0 && nonleaf_node_is_gorged(nodea)) {
         toku_unpin_brtnode_off_client_thread(h, nodeb);
-        flush_some_child(h, nodea, NULL, 0, suppress_leaf_merge);
+        flush_some_child(h, nodea, NULL, 0, started_at_root);
     }
     else if (nodeb->height > 0 && nonleaf_node_is_gorged(nodeb)) {
         toku_unpin_brtnode_off_client_thread(h, nodea);
-        flush_some_child(h, nodeb, NULL, 0, suppress_leaf_merge);
+        flush_some_child(h, nodeb, NULL, 0, started_at_root);
     }
     else {
         toku_unpin_brtnode_off_client_thread(h, nodea);
@@ -2899,7 +2925,7 @@ maybe_merge_pinned_nodes (BRTNODE parent, struct kv_pair *parent_splitk,
 // As output, two of node's children are merged or rebalanced, and node is unlocked
 //
 static void
-brt_merge_child (struct brt_header* h, BRTNODE node, int childnum_to_merge, BOOL *did_react, bool suppress_leaf_merge)
+brt_merge_child (struct brt_header* h, BRTNODE node, int childnum_to_merge, BOOL *did_react, bool started_at_root)
 {
     if (node->n_children < 2) {
         toku_unpin_brtnode_off_client_thread(h, node);
@@ -2944,10 +2970,10 @@ brt_merge_child (struct brt_header* h, BRTNODE node, int childnum_to_merge, BOOL
     }
 
     if (toku_bnc_n_entries(BNC(node,childnuma))>0) {
-        flush_this_child(h, node, childa, childnuma);
+        flush_this_child(h, node, childa, childnuma, started_at_root);
     }
     if (toku_bnc_n_entries(BNC(node,childnumb))>0) {
-        flush_this_child(h, node, childb, childnumb);
+        flush_this_child(h, node, childb, childnumb, started_at_root);
     }
 
 
@@ -3030,7 +3056,7 @@ brt_merge_child (struct brt_header* h, BRTNODE node, int childnum_to_merge, BOOL
         toku_unpin_brtnode_off_client_thread(h, childb);
     }
     if (childa->height > 0 && nonleaf_node_is_gorged(childa)) {
-        flush_some_child(h, childa, NULL, 0, suppress_leaf_merge);
+        flush_some_child(h, childa, NULL, 0, started_at_root);
     }
     else {
         toku_unpin_brtnode_off_client_thread(h, childa);
@@ -3228,7 +3254,7 @@ update_flush_status(BRTNODE UU(parent), BRTNODE child, int cascades)
 }
 
 static void
-flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int cascades, bool suppress_leaf_merge)
+flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int cascades, bool started_at_root)
 // Effect: This function does the following:
 //   - Pick a child of parent (the heaviest child), 
 //   - flush from parent to child, 
@@ -3273,7 +3299,9 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
     // for test
     call_flusher_thread_callback(ft_flush_after_child_pin);
 
-    maybe_destroy_child_blbs(parent, child);
+    if (!started_at_root) {
+        maybe_destroy_child_blbs(parent, child);
+    }
 
     //Note that at this point, we don't have the entire child in.
     // Let's do a quick check to see if the child may be reactive
@@ -3337,7 +3365,7 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
     // it is possible that the flush got rid of some values
     // and now the parent is no longer reactive
     child_re = get_node_reactivity(child);
-    if (suppress_leaf_merge && child->height == 0 && child_re == RE_FUSIBLE) {
+    if (!started_at_root && child->height == 0 && child_re == RE_FUSIBLE) {
         // prevent merging leaf nodes, sometimes (when the cleaner thread
         // called us)
         child_re = RE_STABLE;
@@ -3354,7 +3382,7 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
         // it is the responsibility of flush_some_child to unpin parent
         //
         if (child->height > 0 && nonleaf_node_is_gorged(child)) {
-            flush_some_child(h, child, n_dirtied, cascades+1, suppress_leaf_merge);
+            flush_some_child(h, child, n_dirtied, cascades+1, started_at_root);
         }
         else {
             toku_unpin_brtnode_off_client_thread(h, child);
@@ -3365,7 +3393,7 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
         // it is responsibility of brt_split_child to unlock nodes
         // of parent and child as it sees fit
         //
-        brt_split_child(h, parent, childnum, child, suppress_leaf_merge);
+        brt_split_child(h, parent, childnum, child, started_at_root);
     }
     else if (child_re == RE_FUSIBLE) {
         BOOL did_react;
@@ -3380,7 +3408,7 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
         //
         // it is responsibility of brt_merge_child to unlock parent
         //
-        brt_merge_child(h, parent, childnum, &did_react, suppress_leaf_merge);
+        brt_merge_child(h, parent, childnum, &did_react, started_at_root);
     }
     else {
         assert(FALSE);
@@ -3388,13 +3416,15 @@ flush_some_child (struct brt_header* h, BRTNODE parent, int *n_dirtied, int casc
 }
 
 static void
-flush_this_child (struct brt_header* h, BRTNODE node, BRTNODE child, int childnum)
+flush_this_child (struct brt_header* h, BRTNODE node, BRTNODE child, int childnum, bool started_at_root)
 // Effect: Push everything in the CHILDNUMth buffer of node down into the child.
 {
     update_flush_status(node, child, 0);
     int r;
     toku_assert_entire_node_in_memory(node);
-    maybe_destroy_child_blbs(node, child);
+    if (!started_at_root) {
+        maybe_destroy_child_blbs(node, child);
+    }
     bring_node_fully_into_memory(child, h);
     toku_assert_entire_node_in_memory(child);
     assert(node->height>0);
@@ -3673,7 +3703,7 @@ static void flush_node_fun(void *fe_v)
         // of flush_some_child to unlock the node
         // otherwise, we unlock the node here.
         if (fe->node->height > 0 && nonleaf_node_is_gorged(fe->node)) {
-            flush_some_child(fe->h, fe->node, NULL, 0, false);
+            flush_some_child(fe->h, fe->node, NULL, 0, true);
         }
         else {
             toku_unpin_brtnode_off_client_thread(fe->h,fe->node);
@@ -3684,7 +3714,7 @@ static void flush_node_fun(void *fe_v)
         // bnc, which means we are tasked with flushing some
         // buffer in the node.
         // It is the responsibility of flush_some_child to unlock the node
-        flush_some_child(fe->h, fe->node, NULL, 0, false);
+        flush_some_child(fe->h, fe->node, NULL, 0, true);
     }
     remove_background_job(fe->h->cf, false);
     toku_free(fe);