[$] The ongoing search for mmap_lock scalability

There are certain themes that recur regularly at the Linux Storage,Filesystem, Memory-Management, and BPF Summit; among the most reliable isthe scalability problems posed by the mmap_lock (formerlymmap_sem) lock. This topic has come up in (at least)2013,2018 (twice),and 2019. The 2022 event was noexception, with three consecutive sessions led by Liam Howlett, MichelLespinasse, and Suren Baghdasaryandedicated to the topic. There are improvements on the horizon, but the problemis far from solved.