On Wed, Nov 09, 2011 at 01:09:03AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
>
> This patch pushes the main process context I/O execution into qla_target.c
> qla_tgt_do_work() and splits up interrupt context se_cmd initialization
> into tgt_ops->init_cmd() from I/O dispatch in tgt_ops->handle_cmd().
> The latter will run in process context in qla_tgt_do_work() for
> qla_tgt->qla_tgt_wq without reacquire of qla_hw_data->hardware_lock
Why do you care about initializing the se_cmd in interrupt context?
This has various major downsides:
- we keep calling target core code from interrupt context, which means
we need to keep all the interrupt safe locking there for the long run
- we still have the double workqueue offload when needing to allocate
a session from user context
- you keep the command submission sequence for the drivers messy - I
really want to see the driver having to do a single call into the
target core one day, and not the messy sequence of:
- transport_init_se_cmd
- target_get_sess_cmd
- (set bidi flag in the cmd)
- transport_lookup_cmd_lun
- transport_generic_allocate_tasks
- transport_handle_cdb_direct
All with error handling, sending sense and other little details that
driver writers are guaranteed to get wrong inbetween.
I really want a:
int target_submit_cmd(struct se_session *sess, struct se_cmd *cmd,
struct scsi_lun *lun, u8 *cdb, u8 *sense, int task_attr,
u8 *sense, int data_length, enum dma_data_direction data_dir,
unsigned int flags /* for bidi */);
and not have to have the driver worry about any of the nitty-gritty
details (and yes, we'd need a variant for drivers that already pass
in a SGL list, this is just a high-level concept)
And btw, it's fairly annoying that you keep pushing these patches to the
git tree ASAP while they still are under heavy discussion.
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