static int uncached_add_chunk()

in kernel/uncached.c [73:164]

• 59 lines of code
• 13 McCabe index (conditional complexity)

static int uncached_add_chunk(struct uncached_pool *uc_pool, int nid)
{
	struct page *page;
	int status, i, nchunks_added = uc_pool->nchunks_added;
	unsigned long c_addr, uc_addr;

	if (mutex_lock_interruptible(&uc_pool->add_chunk_mutex) != 0)
		return -1;	/* interrupted by a signal */

	if (uc_pool->nchunks_added > nchunks_added) {
		/* someone added a new chunk while we were waiting */
		mutex_unlock(&uc_pool->add_chunk_mutex);
		return 0;
	}

	if (uc_pool->nchunks_added >= MAX_CONVERTED_CHUNKS_PER_NODE) {
		mutex_unlock(&uc_pool->add_chunk_mutex);
		return -1;
	}

	/* attempt to allocate a granule's worth of cached memory pages */

	page = __alloc_pages_node(nid,
				GFP_KERNEL | __GFP_ZERO | __GFP_THISNODE,
				IA64_GRANULE_SHIFT-PAGE_SHIFT);
	if (!page) {
		mutex_unlock(&uc_pool->add_chunk_mutex);
		return -1;
	}

	/* convert the memory pages from cached to uncached */

	c_addr = (unsigned long)page_address(page);
	uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;

	/*
	 * There's a small race here where it's possible for someone to
	 * access the page through /dev/mem halfway through the conversion
	 * to uncached - not sure it's really worth bothering about
	 */
	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
		SetPageUncached(&page[i]);

	flush_tlb_kernel_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);

	status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
	if (status == PAL_VISIBILITY_OK_REMOTE_NEEDED) {
		atomic_set(&uc_pool->status, 0);
		smp_call_function(uncached_ipi_visibility, uc_pool, 1);
		if (atomic_read(&uc_pool->status))
			goto failed;
	} else if (status != PAL_VISIBILITY_OK)
		goto failed;

	preempt_disable();

	flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);

	/* flush the just introduced uncached translation from the TLB */
	local_flush_tlb_all();

	preempt_enable();

	status = ia64_pal_mc_drain();
	if (status != PAL_STATUS_SUCCESS)
		goto failed;
	atomic_set(&uc_pool->status, 0);
	smp_call_function(uncached_ipi_mc_drain, uc_pool, 1);
	if (atomic_read(&uc_pool->status))
		goto failed;

	/*
	 * The chunk of memory pages has been converted to uncached so now we
	 * can add it to the pool.
	 */
	status = gen_pool_add(uc_pool->pool, uc_addr, IA64_GRANULE_SIZE, nid);
	if (status)
		goto failed;

	uc_pool->nchunks_added++;
	mutex_unlock(&uc_pool->add_chunk_mutex);
	return 0;

	/* failed to convert or add the chunk so give it back to the kernel */
failed:
	for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
		ClearPageUncached(&page[i]);

	free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
	mutex_unlock(&uc_pool->add_chunk_mutex);
	return -1;
}