Get rid of download_mutex

src/Interpreters/Cache/FileSegment.cpp

@@ -132,10 +132,6 @@ size_t FileSegment::getDownloadedSize() const
 
 size_t FileSegment::getDownloadedSizeUnlocked(const FileSegmentGuard::Lock &) const
 {
-    if (download_state == State::DOWNLOADED)
-        return downloaded_size;
-
-    std::unique_lock download_lock(download_mutex);
     return downloaded_size;
 }
 
@@ -357,8 +353,6 @@ void FileSegment::write(const char * from, size_t size, size_t offset)
     {
         cache_writer->write(from, size);
 
-        std::unique_lock download_lock(download_mutex);
-
         cache_writer->next();
 
         downloaded_size += size;

src/Interpreters/Cache/FileSegment.h

@@ -317,7 +317,7 @@ private:
     LocalCacheWriterPtr cache_writer;
 
     /// downloaded_size should always be less or equal to reserved_size
-    size_t downloaded_size = 0;
+    std::atomic<size_t> downloaded_size = 0;
     size_t reserved_size = 0;
 
     /// global locking order rule:
@@ -328,14 +328,6 @@ private:
     LockedKeyCreatorPtr locked_key_creator;
     std::condition_variable cv;
 
-    /// Protects downloaded_size access with actual write into fs.
-    /// downloaded_size is not protected by download_mutex in methods which
-    /// can never be run in parallel to FileSegment::write() method
-    /// as downloaded_size is updated only in FileSegment::write() method.
-    /// Such methods are identified by isDownloader() check at their start,
-    /// e.g. they are executed strictly by the same thread, sequentially.
-    mutable std::mutex download_mutex;
-
     Key file_key;
     const std::string file_path;
     FileCache * cache;