iblock

The very first sight of iblock was iblock_emulate_sync_cache() calling submit_bio(). And I found that iblock_do_task() did the very same thing as I did to call submit_bio() at SCSI host target module.

Let's take a look at how iblock_do_task() works:

// source linux-2.6.32-279.el6 iblock_do_task()
{..
    for_each_sg(task->task_sg, sg, task->task_sg_nents, i) {
...}

iblock_bio_done
{...
    iblock_bio_done();
    if (!atomic_dec_and_test(&ibr->ib_bio_cnt))
        return;
 ...}



transport_allocate_data_tasks()

struct fc4_prov ft_prov = {
    .prli = ft_prli,
    .prlo = ft_prlo,
    .recv = ft_recv,
    .module = THIS_MODULE,
};

ft_init() -> fc_fc4_register_provider(FC_TYPE_FCP, &ft_prov)

ft_recv() ->
ft_recv_req() ->
ft_recv_cmd() ->
ft_send_work() ->
[transport_generic_allocate_tasks()->
transport_generic_cmd_sequencer()] ->
transport_handle_cdb_direct() -> 
transport_generic_new_cmd()->
[transport_allocate_data_tasks -> list_add_tail(&task->t_list, &cmd->t_task_list)] ->
transport_execute_tasks ->
__transport_execute_tasks

__transport_execute_tasks()
{...
    if (cmd->execute_task)
        error = cmd->execute_task(task); // -> iblock_do_task
    else
        error = dev->transport->do_task(task); // -> iblock_emulate_sync_cache
}

ref: http://linux-iscsi.org/wiki/Target