diff --git a/fs/xfs/scrub/repair.c b/fs/xfs/scrub/repair.c
index 1c8eecf..6acf1bf 100644
--- a/fs/xfs/scrub/repair.c
+++ b/fs/xfs/scrub/repair.c
@@ -768,18 +768,23 @@
 		if (!uuid_equal(&btblock->bb_u.s.bb_uuid,
 				&mp->m_sb.sb_meta_uuid))
 			goto out;
+		/*
+		 * Read verifiers can reference b_ops, so we set the pointer
+		 * here.  If the verifier fails we'll reset the buffer state
+		 * to what it was before we touched the buffer.
+		 */
+		bp->b_ops = fab->buf_ops;
 		fab->buf_ops->verify_read(bp);
 		if (bp->b_error) {
+			bp->b_ops = NULL;
 			bp->b_error = 0;
 			goto out;
 		}
 
 		/*
 		 * Some read verifiers will (re)set b_ops, so we must be
-		 * careful not to blow away any such assignment.
+		 * careful not to change b_ops after running the verifier.
 		 */
-		if (!bp->b_ops)
-			bp->b_ops = fab->buf_ops;
 	}
 
 	/*
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 1f9857e..4f5f2ff 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -776,10 +776,26 @@
 }
 
 /*
+ * Set buffer ops on an unchecked buffer and validate it, if possible.
+ *
  * If the caller passed in an ops structure and the buffer doesn't have ops
  * assigned, set the ops and use them to verify the contents.  If the contents
  * cannot be verified, we'll clear XBF_DONE.  We assume the buffer has no
  * recorded errors and is already in XBF_DONE state.
+ *
+ * Under normal operations, every in-core buffer must have buffer ops assigned
+ * to them when the buffer is read in from disk so that we can validate the
+ * metadata.
+ *
+ * However, there are two scenarios where one can encounter in-core buffers
+ * that don't have buffer ops.  The first is during log recovery of buffers on
+ * a V4 filesystem, though these buffers are purged at the end of recovery.
+ *
+ * The other is online repair, which tries to match arbitrary metadata blocks
+ * with btree types in order to find the root.  If online repair doesn't match
+ * the buffer with /any/ btree type, the buffer remains in memory in DONE state
+ * with no ops, and a subsequent read_buf call from elsewhere will not set the
+ * ops.  This function helps us fix this situation.
  */
 int
 xfs_buf_ensure_ops(