During a reshape or a RAID6 array such as expanding by adding an additional
disk, I/Os to the region of the array which have not yet been reshaped can
stall indefinitely. This is from errors in the stripe_ahead_of_reshape
function causing md to think the I/O is to a region in the actively
undergoing the reshape.
stripe_ahead_of_reshape fails to account for the q disk having a sector
value of 0. By not excluding the q disk from the for loop, raid6 will always
generate a min_sector value of 0, causing a return value which stalls.
The function's max_sector calculation also uses min() when it should use
max(), causing the max_sector value to always be 0. During a backwards
rebuild this can cause the opposite problem where it allows I/O to advance
when it should wait.
Fixing these errors will allow safe I/O to advance in a timely manner and
delay only I/O which is unsafe due to stripes in the middle of undergoing
the reshape.
Fixes: 486f60558607 ("md/raid5: Check all disks in a stripe_head for reshape progress")
Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
Tested-by: Laurence Oberman <loberman@xxxxxxxxxx>
---
drivers/md/raid5.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index dc031d42f53b..26e1e8a5e941 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5892,11 +5892,11 @@ static bool stripe_ahead_of_reshape(struct mddev *mddev, struct r5conf *conf,
int dd_idx;
for (dd_idx = 0; dd_idx < sh->disks; dd_idx++) {
- if (dd_idx == sh->pd_idx)
+ if (dd_idx == sh->pd_idx || dd_idx == sh->qd_idx)
continue;
min_sector = min(min_sector, sh->dev[dd_idx].sector);
- max_sector = min(max_sector, sh->dev[dd_idx].sector);
+ max_sector = max(max_sector, sh->dev[dd_idx].sector);
}
spin_lock_irq(&conf->device_lock);
--
2.43.0
