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>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 119de17..4566b61 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5073,6 +5073,7 @@
mddev->changed = 0;
mddev->degraded = 0;
mddev->safemode = 0;
+ mddev->merge_check_needed = 0;
mddev->bitmap_info.offset = 0;
mddev->bitmap_info.default_offset = 0;
mddev->bitmap_info.chunksize = 0;