[cache_writeback] Support offset within the source and destination devices

block-cache/copier.cc

@@ -10,12 +10,14 @@ using namespace std;
 
 copier::copier(io_engine &engine,
 	       string const &src, string const &dest,
-	       sector_t block_size, size_t mem)
+	       sector_t block_size, size_t mem,
+	       sector_t src_offset, sector_t dest_offset)
 	: pool_(block_size * 512, mem, PAGE_SIZE),
 	  block_size_(block_size),
 	  engine_(engine),
 	  src_handle_(engine_.open_file(src, io_engine::M_READ_ONLY)),
 	  dest_handle_(engine_.open_file(dest, io_engine::M_READ_WRITE)),
+	  src_offset_(src_offset), dest_offset_(dest_offset),
 	  genkey_count_(0)
 {
 }
@@ -45,8 +47,8 @@ copier::issue(copy_op const &op)
 
 	auto r = engine_.issue_io(src_handle_,
 				  io_engine::D_READ,
-				  to_sector(op.src_b),
-				  to_sector(op.src_e),
+				  to_src_sector(op.src_b),
+				  to_src_sector(op.src_e),
 				  data,
 				  key);
 
@@ -151,8 +153,8 @@ copier::wait_successful(io_engine::wait_result const &p)
 		j.op.read_complete = true;
 		if (!engine_.issue_io(dest_handle_,
 				      io_engine::D_WRITE,
-				      to_sector(j.op.dest_b),
-				      to_sector(j.op.dest_b + (j.op.src_e - j.op.src_b)),
+				      to_dest_sector(j.op.dest_b),
+				      to_dest_sector(j.op.dest_b + (j.op.src_e - j.op.src_b)),
 				      j.data,
 				      it->first)) {
 			complete(j);
@@ -177,9 +179,15 @@ copier::complete(copy_job const &j)
 }
 
 sector_t
-copier::to_sector(block_address b) const
+copier::to_src_sector(block_address b) const
 {
-	return b * block_size_;
+	return src_offset_ + b * block_size_;
+}
+
+sector_t
+copier::to_dest_sector(block_address b) const
+{
+	return dest_offset_ + b * block_size_;
 }
 
 unsigned

block-cache/copier.h

@@ -61,13 +61,22 @@ namespace bcache {
 	public:
 		copier(io_engine &engine,
 		       std::string const &src, std::string const &dest,
-		       sector_t block_size, size_t mem);
+		       sector_t block_size, size_t mem,
+		       sector_t src_offset, sector_t dest_offset);
 		~copier();
 
 		sector_t get_block_size() const {
 			return block_size_;
 		}
 
+		sector_t get_src_offset() const {
+			return src_offset_;
+		}
+
+		sector_t get_dest_offset() const {
+			return dest_offset_;
+		}
+
 		// Blocks if out of memory.
 		void issue(copy_op const &op);
 
@@ -83,7 +92,8 @@ namespace bcache {
 		void wait_();
 		void complete(copy_job const &j);
 
-		sector_t to_sector(block_address b) const;
+		sector_t to_src_sector(block_address b) const;
+		sector_t to_dest_sector(block_address b) const;
 		unsigned genkey();
 
 		mempool pool_;
@@ -91,6 +101,8 @@ namespace bcache {
 		io_engine &engine_;
 		io_engine::handle src_handle_;
 		io_engine::handle dest_handle_;
+		sector_t src_offset_;
+		sector_t dest_offset_;
 		unsigned genkey_count_;
 
 		using job_map = std::map<unsigned, copy_job>;