os/KeyValueDB: don't call self.valid() from next() and prev()

In most loops using ObjectMapIteratorImpl, there is a call to valid()
followed by a call to next(), which calls valid() again. Calling
valid() alone is particularly expensive, so don't do it twice if
possible.

Signed-off-by: Piotr Dałek <piotr.dalek@ts.fujitsu.com>

src/kv/KeyValueDB.h

@@ -141,7 +141,7 @@ public:
     virtual int upper_bound(const std::string &after) = 0;
     virtual int lower_bound(const std::string &to) = 0;
     virtual bool valid() = 0;
-    virtual int next() = 0;
+    virtual int next(bool validate=true) = 0;
     virtual std::string key() = 0;
     virtual bufferlist value() = 0;
     virtual int status() = 0;
@@ -193,15 +193,26 @@ public:
 	return false;
       return generic_iter->raw_key_is_prefixed(prefix);
     }
-    int next() {
-      if (valid())
-	return generic_iter->next();
-      return status();
+    // Note that next() and prev() shouldn't validate iters,
+    // it's responsibility of caller to ensure they're valid.
+    int next(bool validate=true) {
+      if (validate) {
+        if (valid())
+          return generic_iter->next();
+        return status();
+      } else {
+        return generic_iter->next();  
+      }      
     }
-    int prev() {
-      if (valid())
-	return generic_iter->prev();
-      return status();
+    
+    int prev(bool validate=true) {
+      if (validate) {
+        if (valid())
+          return generic_iter->prev();
+        return status();
+      } else {
+        return generic_iter->prev();  
+      }      
     }
     std::string key() {
       return generic_iter->key();

src/os/DBObjectMap.cc

@@ -344,7 +344,7 @@ bool DBObjectMap::DBObjectMapIteratorImpl::valid_parent()
   return false;
 }
 
-int DBObjectMap::DBObjectMapIteratorImpl::next()
+int DBObjectMap::DBObjectMapIteratorImpl::next(bool validate)
 {
   assert(cur_iter->valid());
   assert(valid());

src/os/DBObjectMap.h

@@ -347,7 +347,7 @@ private:
     int upper_bound(const string &after) { return 0; }
     int lower_bound(const string &to) { return 0; }
     bool valid() { return false; }
-    int next() { assert(0); return 0; }
+    int next(bool validate=true) { assert(0); return 0; }
     string key() { assert(0); return ""; }
     bufferlist value() { assert(0); return bufferlist(); }
     int status() { return 0; }
@@ -385,7 +385,7 @@ private:
     int upper_bound(const string &after);
     int lower_bound(const string &to);
     bool valid();
-    int next();
+    int next(bool validate=true);
     string key();
     bufferlist value();
     int status();

src/os/GenericObjectMap.cc

@@ -415,7 +415,7 @@ bool GenericObjectMap::GenericObjectMapIteratorImpl::valid_parent()
   return false;
 }
 
-int GenericObjectMap::GenericObjectMapIteratorImpl::next()
+int GenericObjectMap::GenericObjectMapIteratorImpl::next(bool validate)
 {
   assert(cur_iter->valid());
   assert(valid());

src/os/GenericObjectMap.h

@@ -298,7 +298,7 @@ private:
     int upper_bound(const string &after) { return 0; }
     int lower_bound(const string &to) { return 0; }
     bool valid() { return false; }
-    int next() { assert(0); return 0; }
+    int next(bool validate=true) { assert(0); return 0; }
     string key() { assert(0); return ""; }
     bufferlist value() { assert(0); return bufferlist(); }
     int status() { return 0; }
@@ -337,7 +337,7 @@ private:
     int upper_bound(const string &after);
     int lower_bound(const string &to);
     bool valid();
-    int next();
+    int next(bool validate=true);
     string key();
     bufferlist value();
     int status();

src/os/MemStore.h

@@ -271,7 +271,7 @@ private:
       std::lock_guard<std::mutex>(o->omap_mutex);
       return it != o->omap.end();      
     }
-    int next() {
+    int next(bool validate=true) {
       std::lock_guard<std::mutex>(o->omap_mutex);
       ++it;
       return 0;

src/os/newstore/NewStore.cc

@@ -1708,7 +1708,7 @@ bool NewStore::OmapIteratorImpl::valid()
   }
 }
 
-int NewStore::OmapIteratorImpl::next()
+int NewStore::OmapIteratorImpl::next(bool validate)
 {
   RWLock::RLocker l(c->lock);
   if (o->onode.omap_head) {

src/os/newstore/NewStore.h

@@ -124,7 +124,7 @@ public:
     int upper_bound(const string &after);
     int lower_bound(const string &to);
     bool valid();
-    int next();
+    int next(bool validate=true);
     string key();
     bufferlist value();
     int status() {