From a2121ebbc8ab7b41f0ffcd724b46ab778aa54efa Mon Sep 17 00:00:00 2001
From: Matan Breizman <mbreizma@redhat.com>
Date: Mon, 12 May 2025 11:14:47 +0000
Subject: [PATCH] crimson/osd/pg: set log_entry_update_waiting_on prior to
 sending requests

Before this patch, we would first send the MOSDPGUpdateLogMissing to
all peers and only then insert this rep_tid to log_entry_update_waiting_on.

This could have resulted in race where we receive the reply prior to
actually inserting the rep_tid.
The reply would have been discarded with "reply on unknown tid" (which
is now aborting).
The unhandled reply would have not let submit_error to return and would
keep holding the lock on this obc.

Fixes: https://tracker.ceph.com/issues/71204

Signed-off-by: Matan Breizman <mbreizma@redhat.com>
---
 src/crimson/osd/pg.cc | 32 +++++++++++++++++++++++---------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/src/crimson/osd/pg.cc b/src/crimson/osd/pg.cc
index 961f92a133050..f85ee660abbcd 100644
--- a/src/crimson/osd/pg.cc
+++ b/src/crimson/osd/pg.cc
@@ -1093,8 +1093,26 @@ PG::interruptible_future<eversion_t> PG::submit_error_log(
     log_entries, t, peering_state.get_pg_trim_to(),
     peering_state.get_pg_committed_to());
 
-
   set<pg_shard_t> waiting_on;
+
+  waiting_on.insert(pg_whoami);
+
+  // preapre log_entry_update_waiting_on prior to sending requests
+  for (const auto &peer: get_acting_recovery_backfill()) {
+    if (peer == pg_whoami) {
+      continue;
+    }
+    ceph_assert(peering_state.get_peer_missing().count(peer));
+    ceph_assert(peering_state.has_peer_info(peer));
+    waiting_on.insert(peer);
+  }
+
+  DEBUGDPP("inserting rep_tid {} waiting on {}", *this, rep_tid, waiting_on);
+  log_entry_update_waiting_on.insert(
+    std::make_pair(rep_tid,
+                   log_update_t{std::move(waiting_on)}));
+
+  // Send missing_requests to peers
   for (const auto &peer: get_acting_recovery_backfill()) {
     if (peer == pg_whoami) {
       continue;
@@ -1110,7 +1128,6 @@ PG::interruptible_future<eversion_t> PG::submit_error_log(
       rep_tid,
       peering_state.get_pg_trim_to(),
       peering_state.get_pg_committed_to());
-    waiting_on.insert(peer);
 
     DEBUGDPP("sending log missing_request (rep_tid: {} entries: {}) to osd {}",
 	     *this, rep_tid, log_entries, peer.osd);
@@ -1120,11 +1137,7 @@ PG::interruptible_future<eversion_t> PG::submit_error_log(
 	std::move(log_m),
 	get_osdmap_epoch()));
   }
-  waiting_on.insert(pg_whoami);
-  DEBUGDPP("inserting rep_tid {}", *this, rep_tid);
-  log_entry_update_waiting_on.insert(
-    std::make_pair(rep_tid,
-		   log_update_t{std::move(waiting_on)}));
+
   co_await interruptor::make_interruptible(
     shard_services.get_store().do_transaction(
       get_collection_ref(), std::move(t)
@@ -1471,8 +1484,9 @@ PG::interruptible_future<> PG::do_update_log_missing_reply(
       log_entry_update_waiting_on.erase(it);
     }
   } else {
-    logger().error("{} : {} got reply {} on unknown tid {}",
-      __func__, peering_state.get_info().pgid, *m, m->get_tid());
+   ceph_abort_msg(fmt::format(
+     "{} : {} got reply {} on unknown tid {}",
+     __func__, peering_state.get_info().pgid, *m, m->get_tid()));
   }
   return seastar::now();
 }
-- 
2.39.5