[$] An operations structure for swap devices

One of the ideas raised at the 2026 LinuxStorage, Filesystem, Memory Management, and BPF Summit (LSFMM+BPF) wasthe creation of anoperations structure for the swap subsystem. Like many parts of thekernel, the swap layer evolved over time, with pieces being added asneeded; the end result of this evolution is rarely what one would expecthad the subsystem been designed today. The interface between the swaplayer and the devices it uses is just one example. It appears that oneresult of the swap subsystem's evolution - the lack of an abstraction layerto interface with underlying storage - will soon be addressed, but in adifferent way than was initially envisioned.