From 9016932fef255207c61e48621629b7d275970ec5 Mon Sep 17 00:00:00 2001
From: Samuel Just <sjust@redhat.com>
Date: Thu, 20 Aug 2020 12:38:20 -0700
Subject: [PATCH] crimson/os/seastore/transaction_manager: only add pin if not
 already pending

If it's already pending, cache.duplicate_for_write is a noop and the extent
will already have a pin.  Also, add some debugging.

Signed-off-by: Samuel Just <sjust@redhat.com>
---
 src/crimson/os/seastore/transaction_manager.h | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/crimson/os/seastore/transaction_manager.h b/src/crimson/os/seastore/transaction_manager.h
index c9c2eb0f594..5b6f03f1151 100644
--- a/src/crimson/os/seastore/transaction_manager.h
+++ b/src/crimson/os/seastore/transaction_manager.h
@@ -136,10 +136,25 @@ public:
 
   /// Obtain mutable copy of extent
   LogicalCachedExtentRef get_mutable_extent(Transaction &t, LogicalCachedExtentRef ref) {
+    auto &logger = crimson::get_logger(ceph_subsys_filestore);
     auto ret = cache.duplicate_for_write(
       t,
       ref)->cast<LogicalCachedExtent>();
-    ret->set_pin(ref->get_pin().duplicate());
+    if (!ret->has_pin()) {
+      logger.debug(
+	"{}: duplicating {} for write: {}",
+	__func__,
+	*ref,
+	*ret);
+      ret->set_pin(ref->get_pin().duplicate());
+    } else {
+      logger.debug(
+	"{}: {} already pending",
+	__func__,
+	*ref);
+      assert(ref->is_pending());
+      assert(&*ref == &*ret);
+    }
     return ret;
   }