Re: highmem pages

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

Jeff Garzik wrote:
> 
> Here is an interesting code snippet from ide-scsi, that could be useful 
> in libata:
> 
>>                 count = min(pc->sg->length - pc->b_count, bcount);
>>                 if (PageHighMem(pc->sg->page)) {
>>                         unsigned long flags;
>>
>>                         local_irq_save(flags);
>>                         buf = kmap_atomic(pc->sg->page, KM_IRQ0) + 
>> pc->sg->offse
>> t;
>>                         drive->hwif->atapi_input_bytes(drive, buf + 
>> pc->b_count,
>>  count);
>>                         kunmap_atomic(buf - pc->sg->offset, KM_IRQ0);
>>                         local_irq_restore(flags);
>>                 } else {
>>                         buf = page_address(pc->sg->page) + 
>> pc->sg->offset;
>>                         drive->hwif->atapi_input_bytes(drive, buf + 
>> pc->b_count,
>>  count);
>>                }
> 

Thanks for the advice. The kmap_atomic() usage optimization patches are ready:

   patch 1/3: reorganize ata_pio_sector() and __atapi_pio_bytes()
   patch 2/3: reorganize "buf + offset"
   patch 3/3: use PageHighMem() to optimize the kmap_atomic() usage

Patch against libata-dev irq-pio branch (c71c18576d0d8aa4db876c737c3c597c724cf02f).
For your review and advice, thanks.

Albert