md/raid5: Allow degraded raid6 to do rmw

Degraded raid6 always do reconstruct-write now. With raid6 xor supported,
we can do rmw in degraded raid6. This patch can reduce many read IOs to
improve performance.

If the failed disk is P, Q or the disk we want to write to, we may need to
do reconstruct-write in max degraded raid6. In this situation we can not
read enough data from handle_stripe_dirtying() so we have to set force_rcw
in handle_stripe_fill() to read all data.

Reviewed-by: Alex Wu <[email protected]>
Reviewed-by: BingJing Chang <[email protected]>
Reviewed-by: Danny Shih <[email protected]>
Signed-off-by: ChangSyun Peng <[email protected]>
Signed-off-by: Song Liu <[email protected]>

0 files changed, 0 insertions, 0 deletions