Implement the cache feature for Page FTL

[BlaCkinkGJ]

Page FTL has not been finished implementing the cache feature. It needs to implement.

Moreover, its architecture's cache shares read and write routines. The cache only can be updated by the write routine. In other words, the current cache implementation cannot efficiently absorb the I/O performance degradation.

Flash-Translation-Layer/ftl/page/page-read.c

Lines 82 to 92 in 964e3b5

	#ifdef PAGE_FTL_USE_CACHE
	cached = (struct device_request *)lru_get(pgftl->cache, lpn);
	if (cached) {
	memcpy(request->data, &((char *)cached->data)[offset],
	request->data_len);
	ret = request->data_len;
	device_free_request(request);
	pthread_mutex_unlock(&pgftl->mutex);
	goto exception;
	}
	#endif

[BlaCkinkGJ]

This part needs to rewrite for cache implementation.

Flash-Translation-Layer/ftl/page/page-write.c

Lines 250 to 256 in 964e3b5

	#else
	ret = dev->d_op->write(dev, request);
	if (ret != (ssize_t)device_get_page_size(dev)) {
	pr_err("device write failed (ppn: %u)\n", request->paddr.lpn);
	return ret;
	}
	#endif

[BlaCkinkGJ]

It also needs to rewrite.

Flash-Translation-Layer/ftl/page/page-core.c

Lines 201 to 223 in 5da4cbb

	#ifdef PAGE_FTL_USE_CACHE
	static int page_ftl_lru_dealloc_fn(const uint64_t key, uintptr_t value)
	{
	struct device_request *request;
	struct page_ftl *pgftl;
	struct device *dev;
	int ret = 0;
	(void)key;
	request = (struct device_request *)value;
	pgftl = (struct page_ftl *)request->rq_private;
	dev = pgftl->dev;
	ret = dev->d_op->write(dev, request);
	if (ret != (ssize_t)device_get_page_size(dev)) {
	pr_err("device write failed (ppn: %u)\n", request->paddr.lpn);
	return ret;
	}
	return 0;
	}
	#endif