md: prevent incorrect update of resync/recovery offset

JIRA: https://issues.redhat.com/browse/RHEL-94433

commit 7202082
Author: Li Nan <linan122@huawei.com>
Date:   Thu Sep 4 15:34:52 2025 +0800

    md: prevent incorrect update of resync/recovery offset

    In md_do_sync(), when md_sync_action returns ACTION_FROZEN, subsequent
    call to md_sync_position() will return MaxSector. This causes
    'curr_resync' (and later 'recovery_offset') to be set to MaxSector too,
    which incorrectly signals that recovery/resync has completed, even though
    disk data has not actually been updated.

    To fix this issue, skip updating any offset values when the sync action
    is FROZEN. The same holds true for IDLE.

    Fixes: 7d9f107 ("md: use new helpers in md_do_sync()")
    Signed-off-by: Li Nan <linan122@huawei.com>
    Link: https://lore.kernel.org/linux-raid/20250904073452.3408516-1-linan666@huaweicloud.com
    Signed-off-by: Yu Kuai <yukuai3@huawei.com>

Signed-off-by: Nigel Croxon <ncroxon@redhat.com>

Author: ncroxon

drivers/md/md.c

@@ -9151,6 +9151,11 @@ void md_do_sync(struct md_thread *thread)
 	}
 
 	action = md_sync_action(mddev);
+	if (action == ACTION_FROZEN || action == ACTION_IDLE) {
+		set_bit(MD_RECOVERY_INTR, &mddev->recovery);
+		goto skip;
+	}
+
 	desc = md_sync_action_name(action);
 	mddev->last_sync_action = action;