dm: optimize dm_mq_queue_rq()

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DM multipath is the only dm-mq target.  But that aside, request-based DM
only supports tables with a single target that is immutable.  Leverage
this fact in dm_mq_queue_rq() by using the 'immutable_target' stored in
the mapped_device when the table was made active.  This saves the need
to even take the read-side of the SRCU via dm_{get,put}_live_table.

If the active DM table does not have an immutable target (e.g. "error"
target was swapped in) then fallback to the slow-path where the target
is looked up from the live table.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

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This commit is contained in:

Mike Snitzer 2016-01-31 17:22:27 -05:00

parent f083b09b78

commit 16f122661d

4 changed files with 31 additions and 23 deletions

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3

drivers/md/dm-mpath.c

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10

drivers/md/dm-table.c

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40

drivers/md/dm.c

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1

drivers/md/dm.h

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