From 65be614f2bfd65a1f13205a3075c87acc72c4836 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@redhat.com>
Date: Tue, 3 Oct 2017 11:18:17 -0500
Subject: [PATCH] os/bluestore: add bluestore_bluefs_min_free

We need at least ~1GB free so we can write out new SSTs (which are 256MB
each).

Signed-off-by: Sage Weil <sage@redhat.com>
---
 src/common/options.cc         |  4 ++++
 src/os/bluestore/BlueStore.cc | 17 +++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/common/options.cc b/src/common/options.cc
index 4a5aca9538f2..a8828ea761d3 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -3146,6 +3146,10 @@ std::vector<Option> get_global_options() {
     .set_default(1_G)
     .set_description("minimum disk space allocated to BlueFS (e.g., at mkfs)"),
 
+    Option("bluestore_bluefs_min_free", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+    .set_default(1_G)
+    .set_description("minimum free space allocated to BlueFS"),
+
     Option("bluestore_bluefs_min_ratio", Option::TYPE_FLOAT, Option::LEVEL_ADVANCED)
     .set_default(.02)
     .set_description("Minimum fraction of free space devoted to BlueFS"),
diff --git a/src/os/bluestore/BlueStore.cc b/src/os/bluestore/BlueStore.cc
index 45c053c500a7..e467eb78bed6 100644
--- a/src/os/bluestore/BlueStore.cc
+++ b/src/os/bluestore/BlueStore.cc
@@ -4860,9 +4860,11 @@ int BlueStore::_balance_bluefs_freespace(PExtentVector *extents)
 	     << " > max_ratio " << cct->_conf->bluestore_bluefs_max_ratio
 	     << ", should reclaim " << pretty_si_t(reclaim) << dendl;
   }
+
+  // don't take over too much of the freespace
+  uint64_t free_cap = cct->_conf->bluestore_bluefs_max_ratio * total_free;
   if (bluefs_total < cct->_conf->bluestore_bluefs_min &&
-    cct->_conf->bluestore_bluefs_min <
-      (uint64_t)(cct->_conf->bluestore_bluefs_max_ratio * total_free)) {
+      cct->_conf->bluestore_bluefs_min < free_cap) {
     uint64_t g = cct->_conf->bluestore_bluefs_min - bluefs_total;
     dout(10) << __func__ << " bluefs_total " << bluefs_total
 	     << " < min " << cct->_conf->bluestore_bluefs_min
@@ -4871,6 +4873,17 @@ int BlueStore::_balance_bluefs_freespace(PExtentVector *extents)
       gift = g;
     reclaim = 0;
   }
+  uint64_t min_free = cct->_conf->get_val<uint64_t>("bluestore_bluefs_min_free");
+  if (bluefs_free < min_free &&
+      min_free < free_cap) {
+    uint64_t g = min_free - bluefs_free;
+    dout(10) << __func__ << " bluefs_free " << bluefs_total
+	     << " < min " << min_free
+	     << ", should gift " << pretty_si_t(g) << dendl;
+    if (g > gift)
+      gift = g;
+    reclaim = 0;
+  }
 
   if (gift) {
     // round up to alloc size
-- 
2.47.3