From: ChangSyun Peng <allenpeng@xxxxxxxxxxxx>
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 <alexwu@xxxxxxxxxxxx>
Reviewed-by: BingJing Chang <bingjingc@xxxxxxxxxxxx>
Reviewed-by: Danny Shih <dannyshih@xxxxxxxxxxxx>
Signed-off-by: ChangSyun Peng <allenpeng@xxxxxxxxxxxx>
---
drivers/md/raid5.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 43eedf7..02760f3 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -3538,6 +3538,7 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
struct r5dev *fdev[2] = { &sh->dev[s->failed_num[0]],
&sh->dev[s->failed_num[1]] };
int i;
+ bool force_rcw = (sh->raid_conf->rmw_level == PARITY_DISABLE_RMW);
if (test_bit(R5_LOCKED, &dev->flags) ||
@@ -3596,18 +3597,27 @@ static int need_this_block(struct stripe_head *sh, struct stripe_head_state *s,
* devices must be read.
*/
return 1;
+
+ if (s->failed >= 2 &&
+ (fdev[i]->towrite ||
+ s->failed_num[i] == sh->pd_idx ||
+ s->failed_num[i] == sh->qd_idx) &&
+ !test_bit(R5_UPTODATE, &fdev[i]->flags))
+ /* In max degraded raid6, If the failed disk is P, Q,
+ * or we want to read the failed disk, we need to do
+ * reconstruct-write.
+ */
+ force_rcw = true;
}
- /* If we are forced to do a reconstruct-write, either because
- * the current RAID6 implementation only supports that, or
- * because parity cannot be trusted and we are currently
- * recovering it, there is extra need to be careful.
+ /* If we are forced to do a reconstruct-write, because parity
+ * cannot be trusted and we are currently recovering it, there
+ * is extra need to be careful.
* If one of the devices that we would need to read, because
* it is not being overwritten (and maybe not written at all)
* is missing/faulty, then we need to read everything we can.
*/
- if (sh->raid_conf->level != 6 &&
- sh->raid_conf->rmw_level != PARITY_DISABLE_RMW &&
+ if (!force_rcw &&
sh->sector < sh->raid_conf->mddev->recovery_cp)
/* reconstruct-write isn't being forced */
return 0;
--
2.7.4
