flush internal buffers before auto-saving control file

Otherwise, some pieces may be marked as finished in the control file
though they have not yet been written to the storage file.

This should prevent data loss and corruption when resuming downloads
after an app crash.

Signed-off-by: Ali MJ Al-Nasrawy <alimjalnasrawy@gmail.com>

src/DefaultPieceStorage.cc

@@ -685,7 +685,7 @@ std::shared_ptr<DiskAdaptor> DefaultPieceStorage::getDiskAdaptor()
 
 WrDiskCache* DefaultPieceStorage::getWrDiskCache() { return wrDiskCache_; }
 
-void DefaultPieceStorage::flushWrDiskCacheEntry()
+void DefaultPieceStorage::flushWrDiskCacheEntry(bool releaseEntries)
 {
   if (!wrDiskCache_) {
     return;
@@ -697,7 +697,9 @@ void DefaultPieceStorage::flushWrDiskCacheEntry()
     auto ce = piece->getWrDiskCacheEntry();
     if (ce) {
       piece->flushWrCache(wrDiskCache_);
-      piece->releaseWrCache(wrDiskCache_);
+      if (releaseEntries) {
+        piece->releaseWrCache(wrDiskCache_);
+      }
     }
   }
 }

src/DefaultPieceStorage.h

@@ -234,7 +234,7 @@ public:
 
   virtual WrDiskCache* getWrDiskCache() CXX11_OVERRIDE;
 
-  virtual void flushWrDiskCacheEntry() CXX11_OVERRIDE;
+  virtual void flushWrDiskCacheEntry(bool releaseEntries) CXX11_OVERRIDE;
 
   virtual int32_t getPieceLength(size_t index) CXX11_OVERRIDE;
 

src/PieceStorage.h

@@ -226,8 +226,9 @@ public:
 
   virtual WrDiskCache* getWrDiskCache() = 0;
 
-  // Flushes write disk cache for in-flight piece and evicts them.
-  virtual void flushWrDiskCacheEntry() = 0;
+  // Flushes write disk cache for in-flight piece
+  // and optionally releases the associated cache entries.
+  virtual void flushWrDiskCacheEntry(bool releaseEntries) = 0;
 
   virtual int32_t getPieceLength(size_t index) = 0;
 

src/RequestGroup.cc

@@ -210,7 +210,7 @@ std::pair<error_code::Value, std::string> RequestGroup::downloadResult() const
 void RequestGroup::closeFile()
 {
   if (pieceStorage_) {
-    pieceStorage_->flushWrDiskCacheEntry();
+    pieceStorage_->flushWrDiskCacheEntry(true);
     pieceStorage_->getDiskAdaptor()->closeFile();
   }
 }
@@ -1290,6 +1290,9 @@ bool RequestGroup::doesUploadSpeedExceed()
 void RequestGroup::saveControlFile() const
 {
   if (saveControlFile_) {
+    if (pieceStorage_) {
+      pieceStorage_->flushWrDiskCacheEntry(false);
+    }
     progressInfoFile_->save();
   }
 }

src/UnknownLengthPieceStorage.h

@@ -216,7 +216,7 @@ public:
 
   virtual WrDiskCache* getWrDiskCache() CXX11_OVERRIDE { return nullptr; }
 
-  virtual void flushWrDiskCacheEntry() CXX11_OVERRIDE {}
+  virtual void flushWrDiskCacheEntry(bool releaseEntries) CXX11_OVERRIDE {}
 
   virtual int32_t getPieceLength(size_t index) CXX11_OVERRIDE;
 

test/MockPieceStorage.h

@@ -228,7 +228,7 @@ public:
 
   virtual WrDiskCache* getWrDiskCache() CXX11_OVERRIDE { return 0; }
 
-  virtual void flushWrDiskCacheEntry() CXX11_OVERRIDE {}
+  virtual void flushWrDiskCacheEntry(bool releaseEntries) CXX11_OVERRIDE {}
 
   void setDiskAdaptor(const std::shared_ptr<DiskAdaptor>& adaptor)
   {