From 76c343ba1793f5d87d5b036a57422ee855027318 Mon Sep 17 00:00:00 2001
From: Greg Farnum <greg@inktank.com>
Date: Mon, 9 Sep 2013 11:19:37 -0700
Subject: [PATCH] osd: implement basic caching policies in ReplicatedPG

Right now these are very basic and aren't as sophisticated as we
want them to end up, but we have a skeleton for where to put the
decision-making logic.

Signed-off-by: Greg Farnum <greg@inktank.com>
---
 src/osd/ReplicatedPG.cc | 84 +++++++++++++++++++++++++++++++++--------
 src/osd/ReplicatedPG.h  |  5 ++-
 2 files changed, 72 insertions(+), 17 deletions(-)

diff --git a/src/osd/ReplicatedPG.cc b/src/osd/ReplicatedPG.cc
index a4c725a90a8..bc7e17d3613 100644
--- a/src/osd/ReplicatedPG.cc
+++ b/src/osd/ReplicatedPG.cc
@@ -711,23 +711,28 @@ void ReplicatedPG::do_op(OpRequestRef op)
 	      m->get_object_locator().get_pool(),
 	      m->get_object_locator().nspace),
     &obc, can_create, &snapid);
-  if (r) {
-    if (r == -EAGAIN) {
-      // If we're not the primary of this OSD, and we have
-      // CEPH_OSD_FLAG_LOCALIZE_READS set, we just return -EAGAIN. Otherwise,
-      // we have to wait for the object.
-      if (is_primary() ||
-	  (!(m->get_flags() & CEPH_OSD_FLAG_BALANCE_READS) &&
-	   !(m->get_flags() & CEPH_OSD_FLAG_LOCALIZE_READS))) {
-	// missing the specific snap we need; requeue and wait.
-	assert(!can_create); // only happens on a read
-	hobject_t soid(m->get_oid(), m->get_object_locator().key,
-		       snapid, m->get_pg().ps(),
-		       info.pgid.pool(), m->get_object_locator().nspace);
-	wait_for_missing_object(soid, op);
-	return;
-      }
+
+  if (r == -EAGAIN) {
+    // If we're not the primary of this OSD, and we have
+    // CEPH_OSD_FLAG_LOCALIZE_READS set, we just return -EAGAIN. Otherwise,
+    // we have to wait for the object.
+    if (is_primary() ||
+	(!(m->get_flags() & CEPH_OSD_FLAG_BALANCE_READS) &&
+	 !(m->get_flags() & CEPH_OSD_FLAG_LOCALIZE_READS))) {
+      // missing the specific snap we need; requeue and wait.
+      assert(!can_create); // only happens on a read
+      hobject_t soid(m->get_oid(), m->get_object_locator().key,
+		     snapid, m->get_pg().ps(),
+		     info.pgid.pool(), m->get_object_locator().nspace);
+      wait_for_missing_object(soid, op);
+      return;
     }
+  }
+
+  if (maybe_handle_cache(op, obc, r))
+    return;
+
+  if (r) {
     osd->reply_op_error(op, r);
     return;
   }
@@ -886,6 +891,53 @@ void ReplicatedPG::do_op(OpRequestRef op)
   execute_ctx(ctx);
 }
 
+bool ReplicatedPG::maybe_handle_cache(OpRequestRef op, ObjectContextRef obc,
+                                      int r)
+{
+  switch(pool.info.cache_mode) {
+  case pg_pool_t::CACHEMODE_NONE:
+    return false;
+    break;
+  case pg_pool_t::CACHEMODE_WRITEBACK:
+    if (obc.get()) {
+      return false;
+    } else {
+      do_cache_redirect(op, obc);
+      return true;
+    }
+    break;
+  case pg_pool_t::CACHEMODE_INVALIDATE_FORWARD:
+    do_cache_redirect(op, obc);
+    return true;
+    break;
+  case pg_pool_t::CACHEMODE_READONLY:
+    if (obc.get() && !r) {
+      return false;
+    } else {
+      do_cache_redirect(op, obc);
+      return true;
+    }
+    break;
+  default:
+    assert(0);
+  }
+  return false;
+}
+
+void ReplicatedPG::do_cache_redirect(OpRequestRef op, ObjectContextRef obc)
+{
+  MOSDOp *m = static_cast<MOSDOp*>(op->request);
+  int flags = m->get_flags() & (CEPH_OSD_FLAG_ACK|CEPH_OSD_FLAG_ONDISK);
+  MOSDOpReply *reply = new MOSDOpReply(m, -ENOENT,
+                                       get_osdmap()->get_epoch(), flags);
+  request_redirect_t redir(m->get_object_locator(), pool.info.tier_of);
+  reply->set_redirect(redir);
+  dout(10) << "sending redirect to pool " << pool.info.tier_of << " for op "
+	   << op << dendl;
+  m->get_connection()->get_messenger()->send_message(reply, m->get_connection());
+  return;
+}
+
 void ReplicatedPG::execute_ctx(OpContext *ctx)
 {
   dout(10) << __func__ << " " << ctx << dendl;
diff --git a/src/osd/ReplicatedPG.h b/src/osd/ReplicatedPG.h
index 254b5842ffc..fef3814d93a 100644
--- a/src/osd/ReplicatedPG.h
+++ b/src/osd/ReplicatedPG.h
@@ -619,7 +619,10 @@ protected:
   void write_update_size_and_usage(object_stat_sum_t& stats, object_info_t& oi,
 				   SnapSet& ss, interval_set<uint64_t>& modified,
 				   uint64_t offset, uint64_t length, bool count_bytes);
-  void add_interval_usage(interval_set<uint64_t>& s, object_stat_sum_t& st);  
+  void add_interval_usage(interval_set<uint64_t>& s, object_stat_sum_t& st);
+
+  inline bool maybe_handle_cache(OpRequestRef op, ObjectContextRef obc, int r);
+  void do_cache_redirect(OpRequestRef op, ObjectContextRef obc);
 
   int prepare_transaction(OpContext *ctx);