Re: [PATCH V2] fork: Improve error message for corrupted page tables

[Dave Hansen]

On 8/5/19 8:05 PM, Sai Praneeth Prakhya wrote:
> +static const char * const resident_page_types[NR_MM_COUNTERS] = {
> +     [MM_FILEPAGES]          = "MM_FILEPAGES",
> +     [MM_ANONPAGES]          = "MM_ANONPAGES",
> +     [MM_SWAPENTS]           = "MM_SWAPENTS",
> +     [MM_SHMEMPAGES]         = "MM_SHMEMPAGES",
> +};

One trick to ensure that this gets updated if the names are ever
updated.  You can do:

#define NAMED_ARRAY_INDEX(x)    [x] = __stringify(x),

and

static const char * const resident_page_types[NR_MM_COUNTERS] = {
        NAMED_ARRAY_INDEX(MM_FILE_PAGES),
        NAMED_ARRAY_INDEX(MM_SHMEMPAGES),
        ...
};

That makes sure that any name changes make it into the strings.  Then
stick a:

        BUILD_BUG_ON(NR_MM_COUNTERS != ARRAY_SIZE(resident_page_types));

somewhere.  That makes sure that any new array indexes get a string
added in the array.  Otherwise you get nice, early, compile-time errors.