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dm: always defer request allocation to the owner of the request_queue

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DM already calls blk_mq_alloc_request on the request_queue of the
underlying device if it is a blk-mq device.  But now that we allow drivers
to allocate additional data and initialize it ahead of time we need to do
the same for all drivers.   Doing so and using the new cmd_size
infrastructure in the block layer greatly simplifies the dm-rq and mpath
code, and should also make arbitrary combinations of SQ and MQ devices
with SQ or MQ device mapper tables easily possible as a further step.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Christoph Hellwig
2017-01-22 18:32:46 +01:00
committed by Jens Axboe
parent 4bf58435fa
commit eb8db831be
8 changed files with 85 additions and 344 deletions
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drivers/md/dm.h
+1 -2
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@@ -95,8 +95,7 @@ int dm_setup_md_queue(struct mapped_device *md, struct dm_table *t);
/*
* To check whether the target type is request-based or not (bio-based).
*/
#define dm_target_request_based(t) (((t)->type->map_rq != NULL) || \
((t)->type->clone_and_map_rq != NULL))
#define dm_target_request_based(t) ((t)->type->clone_and_map_rq != NULL)
/*
* To check whether the target type is a hybrid (capable of being