From 5005edf80f88879de36d7f5384d103b1c68b2d82 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@redhat.com>
Date: Thu, 2 Jun 2016 13:55:04 -0400
Subject: [PATCH] os/bluestore: fix buffercache discard bug

Signed-off-by: Sage Weil <sage@redhat.com>
---
 src/os/bluestore/BlueStore.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index 6149752c75b..f94821e0d90 100644
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -455,6 +455,7 @@ void BlueStore::BufferCache::trim(uint64_t keep)
 {
   lru_list_t::iterator i = lru.end();
   if (size) {
+    assert(i != lru.begin());
     --i;
   }
   while (size > keep) {
@@ -503,7 +504,7 @@ void BlueStore::BufferSpace::discard(uint64_t offset, uint64_t length)
 	} else {
 	  _add_buffer(new Buffer(this, b->state, b->seq, end, tail));
 	}
-	cache->size -= length;
+	cache->size -= b->length - front;
 	b->truncate(front);
 	return;
       } else {
-- 
2.39.5