current implementation of open file when opened in O_WRONLY will trun…

…cate the file to zero. This is incorrect behaviour.

We don't see it in the normal scenario as write-back cache is on by default. Hence all the open calls with O_WRONLY will be redirected O_RDWR.
To simulate this turn of the write-back cache and then open file in O_WRONLY.

component/block_cache/block_cache.go

@@ -382,7 +382,7 @@ func (bc *BlockCache) CreateFile(options internal.CreateFileOptions) (*handlemap
 
 // OpenFile: Create a handle for the file user has requested to open
 func (bc *BlockCache) OpenFile(options internal.OpenFileOptions) (*handlemap.Handle, error) {
-	log.Trace("BlockCache::OpenFile : name=%s, flags=%d, mode=%s", options.Name, options.Flags, options.Mode)
+	log.Trace("BlockCache::OpenFile : name=%s, flags=%X, mode=%s", options.Name, options.Flags, options.Mode)
 
 	attr, err := bc.NextComponent().GetAttr(internal.GetAttrOptions{Name: options.Name})
 	if err != nil {
@@ -397,7 +397,7 @@ func (bc *BlockCache) OpenFile(options internal.OpenFileOptions) (*handlemap.Han
 	log.Debug("BlockCache::OpenFile : Size of file handle.Size %v", handle.Size)
 	bc.prepareHandleForBlockCache(handle)
 
-	if options.Flags&os.O_TRUNC != 0 || (options.Flags&os.O_WRONLY != 0 && options.Flags&os.O_APPEND == 0) {
+	if options.Flags&os.O_TRUNC != 0 {
 		// If file is opened in truncate or wronly mode then we need to wipe out the data consider current file size as 0
 		log.Debug("BlockCache::OpenFile : Truncate %v to 0", options.Name)
 		handle.Size = 0