prep dskreqs when adding blocks

src/fellow_log.c

@@ -2258,6 +2258,8 @@ logbuffer_prep_dskreqs(struct fellow_logbuffer *lbuf, unsigned urgent)
 	if (lbuf->dskreqs != NULL)
 		return;
 
+	assert(logbuffer_can(lbuf, LBUF_CAN_FLUSH));
+
 	/*
 	 * when the log region is becoming full, start
 	 * pre-allocating disk blocks. For this, we need
@@ -3065,6 +3067,8 @@ logbuffer_addblks(struct fellow_fd *ffd,
 		assert(n >= 1);
 		AZ(lbuf->active.block);
 	}
+	if(logbuffer_can(lbuf, LBUF_CAN_FLUSH))
+		logbuffer_prep_dskreqs(lbuf, 0);
 }
 
 enum getblk_e {