md: export 'frozen' resync state through sysfs

The md resync engine has a 'frozen' state which ensures that
no resync/recovery.  This is used to avoid races.

Export this state through the 'sync_action' sysfs attribute
so that user-space can benefit and also avoid some races.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 58e0b02..384e4f0 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3306,7 +3306,9 @@ static ssize_t
 action_show(mddev_t *mddev, char *page)
 {
        char *type = "idle";
-       if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
+       if (test_bit(MD_RECOVERY_FROZEN, &mddev->recovery))
+               type = "frozen";
+       else if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) ||
            (!mddev->ro && test_bit(MD_RECOVERY_NEEDED, &mddev->recovery))) {
                if (test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery))
                        type = "reshape";
@@ -3329,7 +3331,12 @@ action_store(mddev_t *mddev, const char *page, size_t len)
        if (!mddev->pers || !mddev->pers->sync_request)
                return -EINVAL;
 
-       if (cmd_match(page, "idle")) {
+       if (cmd_match(page, "frozen"))
+               set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+       else
+               clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
+
+       if (cmd_match(page, "idle") || cmd_match(page, "frozen")) {
                if (mddev->sync_thread) {
                        set_bit(MD_RECOVERY_INTR, &mddev->recovery);
                        md_unregister_thread(mddev->sync_thread);