This happened only if my_write() couldn't write even one byte.
I cannot easily add a .test for this, but I tested by hand before and after the change.


mysys/my_write.c:
  Monty and I could not find a reason why a write should not wait for free disk space
  (if disk is full) because it could not write at least one byte; doing so certainly
  corrupts tables. my_pwrite() and my_fwrite() don't test for -1, so no problem.