From fccd28df371dceffaf6ff7a50422b6a5b1ee126c Mon Sep 17 00:00:00 2001
From: Samuel Just <samuel.just@dreamhost.com>
Date: Thu, 13 Oct 2011 14:35:13 -0700
Subject: [PATCH] PG: Fix log.empty confusion

Previously, log.empty meant that the log.head was everion_t().  However,
it was in a few places used to mean that log.head == log.tail.  Now,
log.empty means log.head == log.tail and log.null() indicates that
log.head is eversion_t().

Signed-off-by: Samuel Just <samuel.just@dreamhost.com>
---
 src/osd/OSD.cc |  2 +-
 src/osd/PG.cc  | 14 +++++++-------
 src/osd/PG.h   |  5 +++++
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
index 780936ddf43bd..9628d5fb41347 100644
--- a/src/osd/OSD.cc
+++ b/src/osd/OSD.cc
@@ -3973,7 +3973,7 @@ void OSD::split_pg(PG *parent, map<pg_t,PG*>& children, ObjectStore::Transaction
     PG *child = p->second;
 
     // fix log bounds
-    if (!child->log.log.empty()) {
+    if (!child->log.empty()) {
       child->log.head = child->log.log.rbegin()->version;
       child->log.tail =  parent->log.tail;
       child->log.backlog = parent->log.backlog;
diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index 0a91c53ad50cb..d2ab9688c3eae 100644
--- a/src/osd/PG.cc
+++ b/src/osd/PG.cc
@@ -391,9 +391,9 @@ void PG::merge_log(ObjectStore::Transaction& t,
 
   // If our log is empty, the incoming log either needs to have a backlog
   // or have not been trimmed
-  assert(!log.empty() || olog.backlog || olog.tail == eversion_t());
+  assert(!log.null() || olog.backlog || olog.tail == eversion_t());
   // If the logs don't overlap, we need both backlogs
-  assert(log.head >= olog.tail || ((log.backlog || log.empty()) && olog.backlog));
+  assert(log.head >= olog.tail || ((log.backlog || log.null()) && olog.backlog));
 
   for (map<hobject_t, Missing::item>::iterator i = missing.missing.begin();
        i != missing.missing.end();
@@ -529,7 +529,7 @@ void PG::merge_log(ObjectStore::Transaction& t,
       
       // move aside divergent items
       list<Log::Entry> divergent;
-      while (!log.log.empty()) {
+      while (!log.empty()) {
 	Log::Entry &oe = *log.log.rbegin();
 	/*
 	 * look at eversion.version here.  we want to avoid a situation like:
@@ -825,7 +825,7 @@ void PG::drop_backlog()
   log.backlog = false;
   info.log_backlog = false;
   
-  while (!log.log.empty()) {
+  while (!log.empty()) {
     Log::Entry &e = *log.log.begin();
     if (e.version > log.tail) break;
 
@@ -2200,7 +2200,7 @@ void PG::read_log(ObjectStore *store)
     
     PG::Log::Entry e;
     bufferlist::iterator p = bl.begin();
-    assert(log.log.empty());
+    assert(log.empty());
     eversion_t last;
     bool reorder = false;
     while (!p.end()) {
@@ -2508,7 +2508,7 @@ void PG::log_weirdness()
 		      << " != info.last_update " << info.last_update
 		      << "\n";
 
-  if (log.log.empty()) {
+  if (log.empty()) {
     // shoudl it be?
     if (log.head != log.tail)
       osd->clog.error() << info.pgid
@@ -3882,7 +3882,7 @@ ostream& operator<<(ostream& out, const PG& pg)
       pg.log.head != pg.info.last_update)
     out << " (info mismatch, " << pg.log << ")";
 
-  if (pg.log.log.empty()) {
+  if (pg.log.empty()) {
     // shoudl it be?
     if (pg.log.head.version - pg.log.tail.version != 0) {
       out << " (log bound mismatch, empty)";
diff --git a/src/osd/PG.h b/src/osd/PG.h
index f57145a1cf7f2..7592176517ab7 100644
--- a/src/osd/PG.h
+++ b/src/osd/PG.h
@@ -457,7 +457,12 @@ public:
       backlog = false;
       log.clear();
     }
+
     bool empty() const {
+      return log.empty();
+    }
+
+    bool null() const {
       return head.version == 0 && head.epoch == 0;
     }
 
-- 
2.39.5