/* Marks address as invalid */
#define FTL_ADDR_INVALID((ftl_addr)-1)
/* Marks LBA as invalid */
#define FTL_LBA_INVALID((uint64_t)-1)
#define FTL_BLOCK_SIZE 4096UL


/*
* ftl的地址空间被表示为64位的整数，从0到based bdev大小的空间会直接映射到base device的lbas，大于这个值的空间表示nv cache的lbas
 */
typedef uint64_t ftl_addddr;

/* Number of LBAs that could be stored in a single block */
#define FTL_NUM_LBA_IN_BLOCK(FTL_BLOCK_SIZE / sizeof(uint64_t))

/*
 * Mapping of physical (actual location on disk) to logical (user's POV) addresses. Used in two main scenarios:
 * - during relocation FTL needs to pin L2P pages (this allows to check which pages to pin) and move still valid blocks
 * (valid map allows for preliminary elimination of invalid physical blocks, but user data could invalidate a location
 * during read/write operation, so actual comparision against L2P needs to be done)
 * - After dirty shutdown the state of the L2P is unknown and needs to be rebuilt - it is done by applying all P2L, taking
 * into account ordering of user writes
 */
struct ftl_p2l_map {
	/* Number of valid LBAs */
	size_t num_valid;
	
	/* P2L map's reference count, prevents premature release of resources during dirty shutdown recovery for open bands */
	size_t ref_cnt;
	
	/* P2L map (only valid for open/relocating bands) */
	union {
		uint64_t *band_map;
		void *chunk_map;
	};

	/* DMA buffer for region's metadata entry */
	union {
	struct ftl_band_md*band_dma_md;
	
	struct ftl_nv_cache_chunk_md*chunk_dma_md;
	};
};