[$] The LRU lock and mmap_sem

The kernel's memory-management subsystem has to manage a great deal ofconcurrency; that leads to an ongoing series of locking challenges thatsometimes seem intractable. Two recurring locking issues - the LRU locksand the mmap_sem lock - were the topic of sessions held during thememory-management track of the 2018 Linux Storage, Filesystem, andMemory-Management Summit. In both cases, it quickly became clear that,while some interesting ideas are being pursued, easysolutions are not on offer.