Add atomic_write_size parameter

src/blockstore/blockstore_disk.cpp

@@ -49,6 +49,8 @@ void blockstore_disk_t::parse_config(std::map<std::string, std::string> & config
     meta_block_target_free_space = parse_size(config["meta_block_target_free_space"]);
     bitmap_granularity = parse_size(config["bitmap_granularity"]);
     meta_format = stoull_full(config["meta_format"]);
+    atomic_write_size = (config.find("atomic_write_size") != config.end()
+        ? parse_size(config["atomic_write_size"]) : 4096);
     if (config.find("data_io") == config.end() &&
         config.find("meta_io") == config.end() &&
         config.find("journal_io") == config.end())

src/blockstore/blockstore_disk.h

@@ -30,6 +30,8 @@ struct blockstore_disk_t
     uint32_t journal_block_size = 4096;
     // Metadata block size - minimum_io_size of the metadata device is the best choice
     uint32_t meta_block_size = 4096;
+    // Atomic write size of the data block device
+    uint32_t atomic_write_size = 4096;
     // Target free space in metadata blocks
     uint32_t meta_block_target_free_space = 800;
     // Sparse write tracking granularity. 4 KB is a good choice. Must be a multiple of disk_alignment

src/blockstore/blockstore_write.cpp

@@ -150,7 +150,7 @@ int blockstore_impl_t::dequeue_write(blockstore_op_t *op)
     // parallel writes to the same object are forbidden anyway
     else if (dsk.disable_data_fsync &&
         op->opcode == BS_OP_WRITE_STABLE &&
-        op->len > 0 && op->len <= dsk.bitmap_granularity /* FIXME atomic_write_size */ &&
+        op->len > 0 && op->len <= dsk.atomic_write_size &&
         (obj->get_writes()->flags == (BS_HEAP_BIG_WRITE|BS_HEAP_STABLE) ||
         obj->get_writes()->flags == (BS_HEAP_INTENT_WRITE|BS_HEAP_STABLE)))
     {