Search notes:

include/linux/part_stat.h

include/linux/part_stat.h essentially defines the struct disk_stats, a few macros that operate on such stats an the inline function part_stat_set_all. 
struct disk_stats {
        u64           nsecs  [NR_STAT_GROUPS];
        unsigned long sectors[NR_STAT_GROUPS];
        unsigned long ios    [NR_STAT_GROUPS];
        unsigned long merges [NR_STAT_GROUPS];
        unsigned long io_ticks;
        local_t       in_flight[2];
};
As of release 6.10, NR_STAT_GROUPS is defined to 4 and corresponds to the four statistics groups defined in include/linux/blk_types.h (enum stat_group):

Index

Fatal error: Uncaught PDOException: SQLSTATE[HY000]: General error: 8 attempt to write a readonly database in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php:78 Stack trace: #0 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(78): PDOStatement->execute(Array) #1 /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php(30): insert_webrequest_('/notes/Linux/ke...', 1759612209, '216.73.216.149', 'Mozilla/5.0 App...', NULL) #2 /home/httpd/vhosts/renenyffenegger.ch/httpsdocs/notes/Linux/kernel/source/include/linux/part_stat_h(48): insert_webrequest() #3 {main} thrown in /home/httpd/vhosts/renenyffenegger.ch/php/web-request-database.php on line 78