dm mpath: add optional "queue_mode" feature

Allow a user to specify an optional feature 'queue_mode <mode>' where
<mode> may be "bio", "rq" or "mq" -- which corresponds to bio-based,
request_fn rq-based, and blk-mq rq-based respectively.

If the queue_mode feature isn't specified the default for the
"multipath" target is still "rq" but if dm_mod.use_blk_mq is set to Y
it'll default to mode "mq".

This new queue_mode feature introduces the ability for each multipath
device to have its own queue_mode (whereas before this feature all
multipath devices effectively had to have the same queue_mode).

This commit also goes a long way to eliminate the awkward (ab)use of
DM_TYPE_*, the associated filter_md_type() and other relatively fragile
and difficult to maintain code.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer
2016-05-24 21:16:51 -04:00
parent bf661be1fc
commit e83068a5fa
7 changed files with 159 additions and 119 deletions

View File

@@ -49,7 +49,7 @@ bool dm_use_blk_mq_default(void);
bool dm_use_blk_mq(struct mapped_device *md);
int dm_old_init_request_queue(struct mapped_device *md);
int dm_mq_init_request_queue(struct mapped_device *md, struct dm_target *immutable_tgt);
int dm_mq_init_request_queue(struct mapped_device *md, struct dm_table *t);
void dm_mq_cleanup_mapped_device(struct mapped_device *md);
void dm_start_queue(struct request_queue *q);