md: be more careful setting MD_CHANGE_CLEAN

When MD_CHANGE_CLEAN is set we might block in md_write_start.
So we should only set it when fairly sure that something will clear
it.

There are two places where it is set so as to encourage a metadata
update to record the progress of resync/recovery.  This should only
be done if the internal metadata update mechanisms are in use, which
can be tested by by inspecting '->persistent'.

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

2 files changed, 4 insertions, 2 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 1742435ce3ae..4518994712c7 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1526,7 +1526,8 @@ void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector)
                    atomic_read(&bitmap->mddev->recovery_active) == 0);
 
         bitmap->mddev->curr_resync_completed = bitmap->mddev->curr_resync;
-        set_bit(MD_CHANGE_CLEAN, &bitmap->mddev->flags);
+        if (bitmap->mddev->persistent)
+                set_bit(MD_CHANGE_CLEAN, &bitmap->mddev->flags);
         sector &= ~((1ULL << CHUNK_BLOCK_SHIFT(bitmap)) - 1);
         s = 0;
         while (s < sector && s < bitmap->mddev->resync_max_sectors) {
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9007651ce175..d636b0a40fac 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -6753,7 +6753,8 @@ void md_do_sync(mddev_t *mddev)
                                    atomic_read(&mddev->recovery_active) == 0);
                         mddev->curr_resync_completed =
                                 mddev->curr_resync;
-                        set_bit(MD_CHANGE_CLEAN, &mddev->flags);
+                        if (mddev->persistent)
+                                set_bit(MD_CHANGE_CLEAN, &mddev->flags);
                         sysfs_notify(&mddev->kobj, NULL, "sync_completed");
                 }