ide tcq for 2.4.19-pre8

Hi,

Fixed a few bugs and missing functionality (recovery) since the initial 2.4 version. Changelog:

- (generic tcq) use list_for_each_safe() in blk_queue_invalidate_tags(), we are removing entries while browsning.
- (ide tcq) remember to honor max depth set.
- (ide tcq) fix auto_poll detection oops
- (ide tcq) enable use of NOP command to clear hardware tag queue on error.
- (ide tcq) hwgroup->rq clearing race
- (ide tcq) refuse to toggle tcq enable flag on busy drive. This will need to be fixed properly by serializing such requests with the normal request queue.

I have tested error recovery, and it works. I've provoked errors at full queue depths, and the code correctly recovered and kept spinning without data loss.

Generic tcq support:

*.kernel.org/pub/linux/kernel/people/axboe/patches/v2.4/2.4.19-pre8/block-tag-2419p8-2.bz2

IDE tcq support:

*.kernel.org/pub/linux/kernel/people/axboe/patches/v2.4/2.4.19-pre8/ide-tag-2419p8-2.bz2

All-in-one:

*.kernel.org/pub/linux/kernel/people/axboe/patches/v2.4/2.4.19-pre8/ide-block-tag-2419p8.bz2

Enjoy,

Jens Axboe