From 87f05bbd3119cae44b3ef05e25495b4e2d771702 Mon Sep 17 00:00:00 2001
From: Matan Breizman <mbreizma@redhat.com>
Date: Sun, 19 Feb 2023 10:49:47 +0000
Subject: [PATCH] crimson/osd: Remove head memeber from ObjectContext

Before this patch, ObjectContext had a head member which was used
to get the head obc of a clone object.
This member caused the head object to being referenced while
attempting to 'clear_replica_obc' (Since we only evict un-referenced
obc from the obc_registery).
This mechanism, of obtaining the head, is no longer needed since
'with_clone_obc' loads the head object context first (using
oid.get_head).

In this commit, head is removed from ObjectContext class and users
are removed as well.

Signed-off-by: Matan Breizman <mbreizma@redhat.com>
(cherry picked from commit e702dc39606bfcc3899307453a6b54af11b8b803)
---
 src/crimson/osd/object_context.h         | 14 +++-----------
 src/crimson/osd/object_context_loader.cc |  1 -
 src/crimson/osd/ops_executer.cc          |  1 -
 3 files changed, 3 insertions(+), 13 deletions(-)

diff --git a/src/crimson/osd/object_context.h b/src/crimson/osd/object_context.h
index 48b28ae665f3f..10cfc667abaca 100644
--- a/src/crimson/osd/object_context.h
+++ b/src/crimson/osd/object_context.h
@@ -62,7 +62,6 @@ class ObjectContext : public ceph::common::intrusive_lru_base<
     hobject_t, ObjectContext, obc_to_hoid<ObjectContext>>>
 {
 public:
-  Ref head; // Ref defined as part of ceph::common::intrusive_lru_base
   ObjectState obs;
   SnapSetContextRef ssc;
   // the watch / notify machinery rather stays away from the hot and
@@ -81,21 +80,14 @@ public:
     return get_oid().is_head();
   }
 
-  Ref get_head_obc() const {
-    return head;
-  }
-
   hobject_t get_head_oid() const {
     return get_oid().get_head();
   }
 
   const SnapSet &get_ro_ss() const {
-    if (is_head()) {
-      ceph_assert(ssc);
-      return ssc->snapset;
-    } else {
-      return head->get_ro_ss();
-    }
+    ceph_assert(is_head());
+    ceph_assert(ssc);
+    return ssc->snapset;
   }
 
   void set_head_state(ObjectState &&_obs, SnapSetContextRef &&_ssc) {
diff --git a/src/crimson/osd/object_context_loader.cc b/src/crimson/osd/object_context_loader.cc
index 23aa00a335312..72612b9ccd959 100644
--- a/src/crimson/osd/object_context_loader.cc
+++ b/src/crimson/osd/object_context_loader.cc
@@ -73,7 +73,6 @@ using crimson::common::local_conf;
        func=std::move(func), head=std::move(head), this]()
       -> load_obc_iertr::future<> {
       auto loaded = get_or_load_obc<State>(clone, existed);
-      clone->head = std::move(head);
       return loaded.safe_then_interruptible(
         [func = std::move(func)](auto clone) {
         return std::move(func)(std::move(clone));
diff --git a/src/crimson/osd/ops_executer.cc b/src/crimson/osd/ops_executer.cc
index 6306a0ac1d73a..5e0c442fe7ff5 100644
--- a/src/crimson/osd/ops_executer.cc
+++ b/src/crimson/osd/ops_executer.cc
@@ -1036,7 +1036,6 @@ std::pair<object_info_t, ObjectContextRef> OpsExecuter::prepare_clone(
     c_obc->obs.oi = static_snap_oi;
     c_obc->obs.exists = true;
     c_obc->ssc = obc->ssc;
-    c_obc->head = obc->head;
     logger().debug("clone_obc: {}", c_obc->obs.oi);
     clone_obc = std::move(c_obc);
   }
-- 
2.39.5