tree 44d100c2eadf2a56794e7b526abeb21d1019baa1
parent ba13da47ffa202784355561f72160a41350e95cc
author NeilBrown <neilb@suse.de> 1332121599 +1100
committer NeilBrown <neilb@suse.de> 1332121599 +1100

md/raid10: handle merge_bvec_fn in member devices.

Currently we don't honour merge_bvec_fn in member devices so if there
is one, we force all requests to be single-page at most.
This is not ideal.

So enhance the raid10 merge_bvec_fn to check that function in children
as well.

This introduces a small problem.  There is no locking around calls
the ->merge_bvec_fn and subsequent calls to ->make_request.  So a
device added between these could end up getting a request which
violates its merge_bvec_fn.

Currently the best we can do is synchronize_sched().  This will work
providing no preemption happens.  If there is preemption, we just
have to hope that new devices are largely consistent with old devices.

Signed-off-by: NeilBrown <neilb@suse.de>