drbd: allow bitmap to change during writeout from resync_finished

Symptom: messages similar to
 "FIXME asender in bm_change_bits_to,
  bitmap locked for 'write from resync_finished' by worker"

If a resync or verify is finished (or aborted), a full bitmap writeout
is triggered.  If we have ongoing local IO, the bitmap may still change
during that writeout, pending and not yet processed acks may cause bits
to be cleared, while new writes may cause bits to be to be set.

To fix this, introduce the drbd_bm_write_copy_pages() variant.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index e343817bc69e..ddd297708194 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -1191,6 +1191,22 @@ int drbd_bm_write_lazy(struct drbd_conf *mdev, unsigned upper_idx) __must_hold(l
 }
 
 /**
+ * drbd_bm_write_copy_pages() - Write the whole bitmap to its on disk location.
+ * @mdev:       DRBD device.
+ *
+ * Will only write pages that have changed since last IO.
+ * In contrast to drbd_bm_write(), this will copy the bitmap pages
+ * to temporary writeout pages. It is intended to trigger a full write-out
+ * while still allowing the bitmap to change, for example if a resync or online
+ * verify is aborted due to a failed peer disk, while local IO continues, or
+ * pending resync acks are still being processed.
+ */
+int drbd_bm_write_copy_pages(struct drbd_conf *mdev) __must_hold(local)
+{
+        return bm_rw(mdev, WRITE, BM_AIO_COPY_PAGES, 0);
+}
+
+/**
  * drbd_bm_write_hinted() - Write bitmap pages with "hint" marks, if they have changed.
  * @mdev:       DRBD device.
  */