md: fix data corruption for raid456 when reshape restart while grow up

Currently, if reshape is interrupted, echo "reshape" to sync_action will
restart reshape from scratch, for example:

echo frozen > sync_action
echo reshape > sync_action

This will corrupt data before reshape_position if the array is growing,
fix the problem by continue reshape from reshape_position.

Reported-by: Peter Neuwirth <reddunur@online.de>
Link: https://lore.kernel.org/linux-raid/e2f96772-bfbc-f43b-6da1-f520e5164536@online.de/
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230512015610.821290-3-yukuai1@huaweicloud.com

diff --git a/drivers/md/md.c b/drivers/md/md.c
index ca0de7ddd9434dc640bd0d8ed3cecd9b660a462a..b7f83784710b26f83b9acfaa306e5cf31e327de8 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4806,11 +4806,21 @@ action_store(struct mddev *mddev, const char *page, size_t len)
                        return -EINVAL;
                err = mddev_lock(mddev);
                if (!err) {
-                       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
+                       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
                                err =  -EBUSY;
-                       else {
+                       } else if (mddev->reshape_position == MaxSector ||
+                                  mddev->pers->check_reshape == NULL ||
+                                  mddev->pers->check_reshape(mddev)) {
                                clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
                                err = mddev->pers->start_reshape(mddev);
+                       } else {
+                               /*
+                                * If reshape is still in progress, and
+                                * md_check_recovery() can continue to reshape,
+                                * don't restart reshape because data can be
+                                * corrupted for raid456.
+                                */
+                               clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
                        }
                        mddev_unlock(mddev);
                }