Re: [PATCH 5/7] libata: move and reduce locking to the pio data xfer functions

[Albert Lee <albertcc@tw.ibm.com>]

Tejun Heo wrote:
> Albert Lee wrote:
> 
>>-static void ata_pio_sector(struct ata_queued_cmd *qc, int last)
>>+static void ata_pio_sector(struct ata_queued_cmd *qc, int last, int lock)
> 
> 
> I think the naming of @lock is a bit confusing here.  @clr_hsm_wq or
> @last_sector, maybe?
> 

How about "irq_handover"? When set to "true", it means the workqueue is going to
handover the control of the port to the irq handler.

> 
>>+		if (lock) {
>>+			tail = 8;
>>+			head = ATA_SECT_SIZE - tail; /* multiple of 8 bytes */
>>+			ap->ops->data_xfer(qc->dev, buf + offset, head, do_write);
>>+			spin_lock_irqsave(ap->lock, irq_flags);
>>+		}
>>+
>>+		ap->ops->data_xfer(qc->dev, buf + offset + head, tail, do_write);
> 
> 
> Aieee, we have to transfer the whole last sector while holding the spin
> lock and IRQ disabled.  That's sad but pushing locking into ->data_xfer
> doesn't sound attractive either.  Any better ideas?
> 
> 

Why need to transfer the last sector as a whole?
Spliting it into 504 (unlocked) + 8 (holding ap->lock) works on my machine...

--
albert