From: Samuel Just <sjust@redhat.com>
Date: Wed, 26 Aug 2020 21:49:34 +0000 (-0700)
Subject: crimson/.../lba_manager/btree: hold a reference to parent until added to cache
X-Git-Tag: v16.1.0~807^2~28
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=c82610c070d35bbec099edcab35632ddaa2c5cc0;p=ceph.git

crimson/.../lba_manager/btree: hold a reference to parent until added to cache

Currently, we need to rely on the Transaction::read_set to ensure cache
residence of a leaf node until TransactionManager adds the logical
extent to the cache.  The next patch, however, will introduce a lazy
flag for Transaction's to enable doing snapshot inconsistent scans
without populating the read_set, so we'll want this to work without
it.

Signed-off-by: Samuel Just <sjust@redhat.com>
---

diff --git a/src/crimson/os/seastore/lba_manager/btree/btree_lba_manager.h b/src/crimson/os/seastore/lba_manager/btree/btree_lba_manager.h
index 8287cfac2797e..7de463026bcb3 100644
--- a/src/crimson/os/seastore/lba_manager/btree/btree_lba_manager.h
+++ b/src/crimson/os/seastore/lba_manager/btree/btree_lba_manager.h
@@ -102,7 +102,9 @@ public:
     CachedExtentRef extent);
 
   void add_pin(LBAPin &pin) final {
-    pin_set.add_pin(reinterpret_cast<BtreeLBAPin*>(&pin)->pin);
+    auto *bpin = reinterpret_cast<BtreeLBAPin*>(&pin);
+    pin_set.add_pin(bpin->pin);
+    bpin->parent = nullptr;
   }
 
 private:
diff --git a/src/crimson/os/seastore/lba_manager/btree/btree_range_pin.h b/src/crimson/os/seastore/lba_manager/btree/btree_range_pin.h
index 3f6b5f12f62da..3fa218fc8cdc7 100644
--- a/src/crimson/os/seastore/lba_manager/btree/btree_range_pin.h
+++ b/src/crimson/os/seastore/lba_manager/btree/btree_range_pin.h
@@ -219,6 +219,15 @@ public:
 
 class BtreeLBAPin : public LBAPin {
   friend class BtreeLBAManager;
+
+  /**
+   * parent
+   *
+   * populated until link_extent is called to ensure cache residence
+   * until add_pin is called.
+   */
+  CachedExtentRef parent;
+
   paddr_t paddr;
   btree_range_pin_t pin;
 
@@ -226,9 +235,10 @@ public:
   BtreeLBAPin() = default;
 
   BtreeLBAPin(
+    CachedExtentRef parent,
     paddr_t paddr,
     lba_node_meta_t &&meta)
-    : paddr(paddr) {
+    : parent(parent), paddr(paddr) {
     pin.set_range(std::move(meta));
   }
 
diff --git a/src/crimson/os/seastore/lba_manager/btree/lba_btree_node_impl.cc b/src/crimson/os/seastore/lba_manager/btree/lba_btree_node_impl.cc
index 4738ae6849ab3..1676a82be077f 100644
--- a/src/crimson/os/seastore/lba_manager/btree/lba_btree_node_impl.cc
+++ b/src/crimson/os/seastore/lba_manager/btree/lba_btree_node_impl.cc
@@ -435,6 +435,7 @@ LBALeafNode::lookup_range_ret LBALeafNode::lookup_range(
     auto begin = i->get_key();
     ret.emplace_back(
       std::make_unique<BtreeLBAPin>(
+	this,
 	val.paddr,
 	lba_node_meta_t{ begin, begin + val.len, 0}));
   }
@@ -473,6 +474,7 @@ LBALeafNode::insert_ret LBALeafNode::insert(
   return insert_ret(
     insert_ertr::ready_future_marker{},
     std::make_unique<BtreeLBAPin>(
+      this,
       val.paddr,
       lba_node_meta_t{ begin, begin + val.len, 0}));
 }