From 2da0c7b97c1234a82eeb4c9c22e3806ab1ad44e3 Mon Sep 17 00:00:00 2001
From: Xuehan Xu <xxhdx1985126@gmail.com>
Date: Tue, 22 Feb 2022 17:43:25 +0800
Subject: [PATCH] crimson/os/seastore/backref: prevent backref extents from
 causing transaction conflicts

Signed-off-by: Xuehan Xu <xxhdx1985126@gmail.com>
---
 src/crimson/os/seastore/backref/backref_tree_node.h | 8 ++++++++
 src/crimson/os/seastore/cache.cc                    | 5 +++++
 src/crimson/os/seastore/cached_extent.h             | 4 ++++
 3 files changed, 17 insertions(+)

diff --git a/src/crimson/os/seastore/backref/backref_tree_node.h b/src/crimson/os/seastore/backref/backref_tree_node.h
index 81977462da110..316787830a1c4 100644
--- a/src/crimson/os/seastore/backref/backref_tree_node.h
+++ b/src/crimson/os/seastore/backref/backref_tree_node.h
@@ -65,6 +65,10 @@ public:
   extent_types_t get_type() const final {
     return TYPE;
   }
+
+  bool may_conflict() const final {
+    return false;
+  }
 };
 using BackrefInternalNodeRef = BackrefInternalNode::Ref;
 
@@ -86,6 +90,10 @@ public:
     return TYPE;
   }
 
+  bool may_conflict() const final {
+    return false;
+  }
+
   const_iterator insert(
     const_iterator iter,
     paddr_t key,
diff --git a/src/crimson/os/seastore/cache.cc b/src/crimson/os/seastore/cache.cc
index c037c062526ad..5b031457f2cb6 100644
--- a/src/crimson/os/seastore/cache.cc
+++ b/src/crimson/os/seastore/cache.cc
@@ -718,6 +718,11 @@ void Cache::invalidate_extent(
     Transaction& t,
     CachedExtent& extent)
 {
+  if (!extent.may_conflict()) {
+    assert(extent.transactions.empty());
+    return;
+  }
+
   LOG_PREFIX(Cache::invalidate_extent);
   bool do_conflict_log = true;
   for (auto &&i: extent.transactions) {
diff --git a/src/crimson/os/seastore/cached_extent.h b/src/crimson/os/seastore/cached_extent.h
index 1ec2b2fd8cd50..f0b88133d3e77 100644
--- a/src/crimson/os/seastore/cached_extent.h
+++ b/src/crimson/os/seastore/cached_extent.h
@@ -192,6 +192,10 @@ public:
     return false;
   }
 
+  virtual bool may_conflict() const {
+    return true;
+  }
+
   friend std::ostream &operator<<(std::ostream &, extent_state_t);
   virtual std::ostream &print_detail(std::ostream &out) const { return out; }
   std::ostream &print(std::ostream &out) const {
-- 
2.39.5