[$] Looking forward to mapcount madness 2025

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