From 128ecc27f242f8a37f717f1249985a8d9742e964 Mon Sep 17 00:00:00 2001
From: Joe Thornber <ejt@redhat.com>
Date: Thu, 28 May 2020 07:38:58 +0100
Subject: [PATCH] [space-maps] remove count_possibly_greater_than_one

This is only ever called with a recursive space map wrapper,
and that causes too many false positives.  False positives trigger
a copy of a metadata page, so this is a false economy.
---
 persistent-data/space-maps/careful_alloc.cc |  4 ----
 persistent-data/space-maps/core.cc          |  6 ------
 persistent-data/space-maps/disk.cc          |  4 ----
 persistent-data/space-maps/noop.h           |  5 -----
 persistent-data/space-maps/recursive.cc     | 10 ----------
 persistent-data/space_map.h                 |  2 --
 persistent-data/transaction_manager.cc      |  2 +-
 7 files changed, 1 insertion(+), 32 deletions(-)

diff --git a/persistent-data/space-maps/careful_alloc.cc b/persistent-data/space-maps/careful_alloc.cc
index 4609883..9e64cb1 100644
--- a/persistent-data/space-maps/careful_alloc.cc
+++ b/persistent-data/space-maps/careful_alloc.cc
@@ -77,10 +77,6 @@ namespace {
 			return sm_->find_free(filtered_it);
 		}
 
-		virtual bool count_possibly_greater_than_one(block_address b) const {
-			return sm_->count_possibly_greater_than_one(b);
-		}
-
 		virtual void extend(block_address extra_blocks) {
 			return sm_->extend(extra_blocks);
 		}
diff --git a/persistent-data/space-maps/core.cc b/persistent-data/space-maps/core.cc
index 6e1418c..463d212 100644
--- a/persistent-data/space-maps/core.cc
+++ b/persistent-data/space-maps/core.cc
@@ -43,7 +43,6 @@ namespace {
 		void inc(block_address b, ref_t count) override;
 		void dec(block_address b, ref_t count) override;
 		maybe_block find_free(span_iterator &it) override;
-		bool count_possibly_greater_than_one(block_address b) const override;
 		void extend(block_address extra_blocks) override;
 		void count_metadata(block_counter &bc) const override;
 
@@ -131,11 +130,6 @@ namespace {
 		return maybe_block();
 	}
 
-	bool
-	core_map::count_possibly_greater_than_one(block_address b) const {
-		return get_count(b) > 1;
-	}
-
 	void
 	core_map::extend(block_address extra_blocks) {
 		throw std::runtime_error("'extend' not implemented");
diff --git a/persistent-data/space-maps/disk.cc b/persistent-data/space-maps/disk.cc
index 51a4b78..28e13d3 100644
--- a/persistent-data/space-maps/disk.cc
+++ b/persistent-data/space-maps/disk.cc
@@ -429,10 +429,6 @@ namespace {
 			return maybe_block();
 		}
 
-		bool count_possibly_greater_than_one(block_address b) const {
-			return get_count(b) > 1;
-		}
-
 		virtual void extend(block_address extra_blocks) {
 			block_address nr_blocks = nr_blocks_ + extra_blocks;
 
diff --git a/persistent-data/space-maps/noop.h b/persistent-data/space-maps/noop.h
index 925936c..8f3660c 100644
--- a/persistent-data/space-maps/noop.h
+++ b/persistent-data/space-maps/noop.h
@@ -64,11 +64,6 @@ namespace persistent_data {
 			return boost::optional<block_address>(0);
 		}
 
-		bool count_possibly_greater_than_one(block_address b) const {
-			fail();
-			return false;
-		}
-
 		void extend(block_address extra_blocks) {
 			fail();
 		}
diff --git a/persistent-data/space-maps/recursive.cc b/persistent-data/space-maps/recursive.cc
index 46d6ed5..dadbe88 100644
--- a/persistent-data/space-maps/recursive.cc
+++ b/persistent-data/space-maps/recursive.cc
@@ -132,16 +132,6 @@ namespace {
 			return sm_->find_free(filtered_it);
 		}
 
-		virtual bool count_possibly_greater_than_one(block_address b) const {
-			recursing_const_lock lock(*this);
-
-			bool gto = sm_->count_possibly_greater_than_one(b);
-			if (gto)
-				return true;
-
-			return modify_count(b, 1) > 1;
-		}
-
 		virtual void extend(block_address extra_blocks) {
 			cant_recurse("extend");
 			recursing_lock lock(*this);
diff --git a/persistent-data/space_map.h b/persistent-data/space_map.h
index 930626a..15b6076 100644
--- a/persistent-data/space_map.h
+++ b/persistent-data/space_map.h
@@ -88,8 +88,6 @@ namespace persistent_data {
 
 		virtual maybe_block find_free(span_iterator &it) = 0;
 
-		virtual bool count_possibly_greater_than_one(block_address b) const = 0;
-
 		virtual void extend(block_address extra_blocks) = 0;
 
 		struct iterator {
diff --git a/persistent-data/transaction_manager.cc b/persistent-data/transaction_manager.cc
index 2bcdda7..a8b6c7b 100644
--- a/persistent-data/transaction_manager.cc
+++ b/persistent-data/transaction_manager.cc
@@ -62,7 +62,7 @@ transaction_manager::new_block(validator v)
 pair<transaction_manager::write_ref, bool>
 transaction_manager::shadow(block_address orig, validator v)
 {
-	bool need_inc = sm_->count_possibly_greater_than_one(orig);
+	bool need_inc = sm_->get_count(orig) > 1;
 	if (is_shadow(orig) && !need_inc)
 		return make_pair(bm_->write_lock(orig, v), need_inc);