[PATCH v2 2/2] md/raid5: preserve active PPL log when removing a replacement

[Yingjie Wang]

raid5_remove_disk() selects either the active member or its
replacement, but then clears the slot PPL log regardless of which
device is being removed. Removing an unpromoted replacement therefore
sets log->rdev to NULL even though the active member remains in the
slot.

ppl_write_stripe() subsequently returns -EAGAIN for that slot, which
lets ops_run_io() dispatch writes without first recording them in PPL.

Only change the PPL log when the active rdev is removed from a slot
that still belongs to the current array width. A slot left beyond
raid_disks after a shrink has no child PPL log, so skip log_modify()
there and still clear the device pointer.

Fixes: 6358c239d88c ("raid5-ppl: support disk hot add/remove with PPL")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Yingjie Wang <x-professor@xxxxxxxxxxx>
---
 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 455e36ddceee..418803741c67 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -8474,12 +8474,12 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
 		err = -EBUSY;
 		goto abort;
 	}
-	WRITE_ONCE(*rdevp, NULL);
-	if (!err) {
+	if (rdev == p->rdev && number < conf->raid_disks) {
 		err = log_modify(conf, rdev, false);
 		if (err)
 			goto abort;
 	}
+	WRITE_ONCE(*rdevp, NULL);
 
 	tmp = p->replacement;
 	if (tmp) {
-- 
2.43.0