From da8f89b914d636b910bcc432abf899d738752f73 Mon Sep 17 00:00:00 2001
From: Samuel Just <sjust@redhat.com>
Date: Wed, 3 Jul 2024 21:26:23 -0700
Subject: [PATCH] crimson/.../pg_interval_interrupt_condition: clarify member,
 add comments

Signed-off-by: Samuel Just <sjust@redhat.com>
(cherry picked from commit b49f82a18b21732dfb18b0714bbfbd94c4b97ba3)
---
 .../osd/pg_interval_interrupt_condition.cc    |  8 ++---
 .../osd/pg_interval_interrupt_condition.h     | 30 +++++++++++++++++--
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/src/crimson/osd/pg_interval_interrupt_condition.cc b/src/crimson/osd/pg_interval_interrupt_condition.cc
index bc54b091494..7a8cceb7f62 100644
--- a/src/crimson/osd/pg_interval_interrupt_condition.cc
+++ b/src/crimson/osd/pg_interval_interrupt_condition.cc
@@ -15,8 +15,8 @@ interrupt_cond<crimson::osd::IOInterruptCondition>;
 
 namespace crimson::osd {
 
-IOInterruptCondition::IOInterruptCondition(Ref<PG>& pg, epoch_t e)
-  : pg(pg), e(e) {}
+IOInterruptCondition::IOInterruptCondition(Ref<PG>& pg, epoch_t epoch_started)
+  : pg(pg), epoch_started(epoch_started) {}
 
 IOInterruptCondition::~IOInterruptCondition() {
   // for the sake of forward declaring PG (which is a detivate of
@@ -26,9 +26,9 @@ IOInterruptCondition::~IOInterruptCondition() {
 bool IOInterruptCondition::new_interval_created() {
   LOG_PREFIX(IOInterruptCondition::new_interval_created);
   const epoch_t interval_start = pg->get_interval_start_epoch();
-  bool ret = e < interval_start;
+  bool ret = epoch_started < interval_start;
   if (ret) {
-    DEBUGDPP("stored interval e{} < interval_start e{}", *pg, e, interval_start);
+    DEBUGDPP("stored epoch_started e{} < interval_start e{}", *pg, epoch_started, interval_start);
   }
   return ret;
 }
diff --git a/src/crimson/osd/pg_interval_interrupt_condition.h b/src/crimson/osd/pg_interval_interrupt_condition.h
index 95b3595cdd0..46323bb52cc 100644
--- a/src/crimson/osd/pg_interval_interrupt_condition.h
+++ b/src/crimson/osd/pg_interval_interrupt_condition.h
@@ -12,15 +12,41 @@ namespace crimson::osd {
 
 class PG;
 
+/**
+ * IOInterruptCondition
+ *
+ * Encapsulates logic for determining whether a continuation chain
+ * started at <epoch_started> should be halted for once of two reasons:
+ * 1. PG instance is stopping (includes if OSD is shutting down)
+ * 2. A map advance has caused an interval change since <epoch_started>
+ *
+ * <epoch_started> should be the epoch at which the operation was logically
+ * started, which may or may not pg->get_osdmap_epoch() at the time at which
+ * with_interruption is actually invoked.
+ */
 class IOInterruptCondition {
 public:
-  IOInterruptCondition(Ref<PG>& pg, epoch_t e);
+  IOInterruptCondition(Ref<PG>& pg, epoch_t epoch_started);
   ~IOInterruptCondition();
 
+  /**
+   * new_interval_created()
+   *
+   * Returns true iff the pg has entered a new interval since <epoch_started>
+   * (<epoch_started> < pg->get_interval_start_epoch())
+   */
   bool new_interval_created();
 
+  /// true iff pg->stopping
   bool is_stopping();
 
+  /**
+   * is_primary
+   *
+   * True iff the pg is still primary.  Used to populate
+   * ::crimson::common::actingset_changed upon interval change
+   * to indicate whether client IOs should be requeued.
+   */
   bool is_primary();
 
   template <typename Fut>
@@ -50,7 +76,7 @@ public:
 
 private:
   Ref<PG> pg;
-  epoch_t e;
+  epoch_t epoch_started;
 };
 
 } // namespace crimson::osd
-- 
2.47.3