[$] The search for available page flags

Among the many other things crammed into the page structurethat is usedto represent a page of memory in the kernel is a set of flags to track thestate of the page. These flags have been in short supply for some time;LWN looked at the problem nearly ten yearsago. Ji(C)rime Glisse ran a session during the memory-management track of the2019 Linux Storage, Filesystem, and Memory-Management Summit to exploreways of making some flags available for new uses. While there may be someeasily available bits in the field that holds the page flags, obtaining asignificant number of them may be tricky.