Re: [PATCH 0/2] libata: switch to block layer tagging

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, May 20 2009, Jeff Garzik wrote:
> Jens Axboe wrote:
>> Hi,
>>
>> This patchset switches libata to block layer tagging. It gets rid of yet
>> another O(N) command loop.
>>
>>  block/blk-tag.c           |   99 +++++++++++++++++++++++++++-----------
>>  drivers/ata/libata-core.c |   94 ++++++++++--------------------------
>>  drivers/ata/libata-scsi.c |   23 ++++++++
>>  drivers/ata/libata.h      |   19 ++++++-
>>  include/linux/blkdev.h    |    3 +
>>  include/linux/libata.h    |    1  6 files changed, 139 insertions(+), 
>> 100 deletions(-)
>
> Will take a look post-sleep...  mainly it's a question of possibly  

:-)

> interfering with SCSI's use of block layer tagging.  Though for the  
> moment I will simply assume you verified that ;)

Certainly, the patch has been used and sitting in my ssd branch for
months now. It essentially just tells SCSI to enable the block layer
tagging for libata devices with ncq. Then libata gets block layer tagged
requests automatically, and it can simply reuse the assigned tag
internally as well.

That part is trivial. The nasty bit is when libata makes up its own tag
for internal issue, that is what patch #2 covers.

-- 
Jens Axboe