From: Patrick Donnelly <pdonnell@redhat.com>
Date: Tue, 9 Jun 2020 23:49:20 +0000 (-0700)
Subject: mds: add maximum random ephemeral pin percentage
X-Git-Tag: wip-pdonnell-testing-20200918.022351~870^2~8
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=c8d343d592de92af91c6f9eecb6aab0ebed54657;p=ceph-ci.git

mds: add maximum random ephemeral pin percentage

This new config is designed to prevent creating too many subtrees from a
random ephemeral pinning policy.

Signed-off-by: Patrick Donnelly <pdonnell@redhat.com>
---

diff --git a/src/common/options.cc b/src/common/options.cc
index 5b232c7f88e..55e4d5539c9 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -8005,6 +8005,13 @@ std::vector<Option> get_mds_options() {
     .set_description("allow ephemeral random pinning of the loaded subtrees")
     .set_long_description("probabilistically pin the loaded directory inode and the subtree beneath it to an MDS based on the consistent hash of the inode number. The higher this value the more likely the loaded subtrees get pinned"),
 
+    Option("mds_export_ephemeral_random_max", Option::TYPE_FLOAT, Option::LEVEL_ADVANCED)
+    .set_default(0.01)
+    .set_flag(Option::FLAG_RUNTIME)
+    .set_description("the maximum percent permitted for random ephemeral pin policy")
+    .set_min_max(0.0, 1.0)
+    .add_see_also("mds_export_ephemeral_random"),
+
     Option("mds_export_ephemeral_distributed", Option::TYPE_BOOL, Option::LEVEL_ADVANCED)
     .set_default(false)
     .set_flag(Option::FLAG_RUNTIME)
diff --git a/src/mds/CInode.cc b/src/mds/CInode.cc
index 39239f8fcd9..03ad469d507 100644
--- a/src/mds/CInode.cc
+++ b/src/mds/CInode.cc
@@ -5514,6 +5514,7 @@ double CInode::get_ephemeral_rand(bool inherit) const
    * have a parent yet.
    */
   const CInode *in = this;
+  double max = mdcache->export_ephemeral_random_max;
   while (true) {
     if (in->is_system())
       break;
@@ -5525,7 +5526,7 @@ double CInode::get_ephemeral_rand(bool inherit) const
       break;
 
     if (in->get_inode().export_ephemeral_random_pin > 0.0)
-      return in->get_inode().export_ephemeral_random_pin;
+      return std::min(in->get_inode().export_ephemeral_random_pin, max);
 
     /* An export_pin overrides only if no closer parent (incl. this one) has a
      * random pin set.
diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index 58ce50128fb..46974b7024d 100644
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -155,6 +155,7 @@ MDCache::MDCache(MDSRank *m, PurgeQueue &purge_queue_) :
 
   export_ephemeral_distributed_config =  g_conf().get_val<bool>("mds_export_ephemeral_distributed");
   export_ephemeral_random_config =  g_conf().get_val<bool>("mds_export_ephemeral_random");
+  export_ephemeral_random_max = g_conf().get_val<double>("mds_export_ephemeral_random_max");
 
   lru.lru_set_midpoint(g_conf().get_val<double>("mds_cache_mid"));
 
@@ -243,6 +244,9 @@ void MDCache::handle_conf_change(const std::set<std::string>& changed, const MDS
     }
     mds->balancer->handle_export_pins();
   }
+  if (changed.count("mds_export_ephemeral_random_max")) {
+    export_ephemeral_random_max = g_conf().get_val<double>("mds_export_ephemeral_random_max");
+  }
   if (changed.count("mds_health_cache_threshold"))
     cache_health_threshold = g_conf().get_val<double>("mds_health_cache_threshold");
   if (changed.count("mds_cache_mid"))
diff --git a/src/mds/MDCache.h b/src/mds/MDCache.h
index 1cce2ac33b5..11fe5b9e3a6 100644
--- a/src/mds/MDCache.h
+++ b/src/mds/MDCache.h
@@ -1001,6 +1001,8 @@ class MDCache {
 
   OpenFileTable open_file_table;
 
+  double export_ephemeral_random_max = 0.0;
+
  protected:
   // track master requests whose slaves haven't acknowledged commit
   struct umaster {
diff --git a/src/mds/MDSRank.cc b/src/mds/MDSRank.cc
index fed587d5d33..73527884f5f 100644
--- a/src/mds/MDSRank.cc
+++ b/src/mds/MDSRank.cc
@@ -3600,6 +3600,7 @@ const char** MDSRankDispatcher::get_tracked_conf_keys() const
     "mds_dump_cache_threshold_formatter",
     "mds_enable_op_tracker",
     "mds_export_ephemeral_random",
+    "mds_export_ephemeral_random_max",
     "mds_export_ephemeral_distributed",
     "mds_health_cache_threshold",
     "mds_inject_migrator_session_race",
diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index a261fc4c311..1b8a2ac0311 100644
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -5675,6 +5675,14 @@ void Server::handle_set_vxattr(MDRequestRef& mdr, CInode *cur)
       return;
     }
 
+    if (val < 0.0 || 1.0 < val) {
+      respond_to_request(mdr, -EDOM);
+      return;
+    } else if (mdcache->export_ephemeral_random_max < val) {
+      respond_to_request(mdr, -EINVAL);
+      return;
+    }
+
     if (!xlock_policylock(mdr, cur))
       return;