static int virtio_mem_sbm_unplug_request()

in virtio_mem.c [2042:2093]

• 36 lines of code
• 8 McCabe index (conditional complexity)

static int virtio_mem_sbm_unplug_request(struct virtio_mem *vm, uint64_t diff)
{
	const int mb_states[] = {
		VIRTIO_MEM_SBM_MB_OFFLINE_PARTIAL,
		VIRTIO_MEM_SBM_MB_OFFLINE,
		VIRTIO_MEM_SBM_MB_MOVABLE_PARTIAL,
		VIRTIO_MEM_SBM_MB_KERNEL_PARTIAL,
		VIRTIO_MEM_SBM_MB_MOVABLE,
		VIRTIO_MEM_SBM_MB_KERNEL,
	};
	uint64_t nb_sb = diff / vm->sbm.sb_size;
	unsigned long mb_id;
	int rc, i;

	if (!nb_sb)
		return 0;

	/*
	 * We'll drop the mutex a couple of times when it is safe to do so.
	 * This might result in some blocks switching the state (online/offline)
	 * and we could miss them in this run - we will retry again later.
	 */
	mutex_lock(&vm->hotplug_mutex);

	/*
	 * We try unplug from partially plugged blocks first, to try removing
	 * whole memory blocks along with metadata. We prioritize ZONE_MOVABLE
	 * as it's more reliable to unplug memory and remove whole memory
	 * blocks, and we don't want to trigger a zone imbalances by
	 * accidentially removing too much kernel memory.
	 */
	for (i = 0; i < ARRAY_SIZE(mb_states); i++) {
		virtio_mem_sbm_for_each_mb_rev(vm, mb_id, mb_states[i]) {
			rc = virtio_mem_sbm_unplug_any_sb(vm, mb_id, &nb_sb);
			if (rc || !nb_sb)
				goto out_unlock;
			mutex_unlock(&vm->hotplug_mutex);
			cond_resched();
			mutex_lock(&vm->hotplug_mutex);
		}
		if (!unplug_online && i == 1) {
			mutex_unlock(&vm->hotplug_mutex);
			return 0;
		}
	}

	mutex_unlock(&vm->hotplug_mutex);
	return nb_sb ? -EBUSY : 0;
out_unlock:
	mutex_unlock(&vm->hotplug_mutex);
	return rc;
}