[$] Some slow progress on get_user_pages()

One of the surest signs that the Linux Storage, Filesystem, andMemory-Management (LSFMM) Summit is approaching is the seasonal migration ofmemory-management developers toward the get_user_pages() problem.This core kernel primitive is necessary for high-performance I/O touser-space memory, but its interactions with filesystems have never beenreliable - or even fully specified. There are currently a couple of patchsets in circulation that are attempting to improve the situation, though afull solution still seems distant.