Recovering from failure in programming a nonvolatile memory

A controller, comprising:

• an interface, which is configured to communicate with a nonvolatile memory comprising multiple memory cells organized in multiple memory blocks, wherein each memory block comprises multiple Word Lines (WLs) of the memory cells;
• and
• a processor, configured to:
• receive first data, and store the first data in one or more WLs of a given memory block, wherein the first data occupies less than a maximal number of WLs available in the given memory block;
• calculate redundancy data over the first data, and store the redundancy data in a dedicated memory;
• receive second data and program the second data to a selected WL of the given memory block that was not programmed with the first data;
• check a programming status resulting from the programming of the selected WL;
• in response to identifying that programming the second data to the selected WL has corrupted at least part of the first data, recover the first data using the redundancy data;
• and
• in response to identifying that programming the second data has filled the given memory block completely, calculate for the given memory block permanent redundancy data, smaller than the redundancy data, and store the permanent redundancy data in the nonvolatile memory.