[$] Looking forward to mapcount madness 2025

One of the many important tasks that the kernel's memory-managementsubsystem must handle is keeping track of how pages of memory are mappedinto the address spaces of the processes running on the system. As long asmappings to a given page exist, that page must be kept in place. As itturns out, tracking these mappings is harder than it seems it should be,and the move to folios within the memory-management subsystem is addingsome complexities of its own. As a follow-up to the "mapcount madness" session that he ran atthe 2024 Linux Storage, Filesystem,Memory-Management, and BPF summit, David Hildenbrand has posted a patch seriesintended to improve the handling of mapping counts for folios - but exactaccounting remains elusive in some situations.