swap 区域预留支持主动卸载 · v1

Some swap backends need memory to accept writes, making them useful for deliberate cold-page offload but unsuitable dependencies for reclaim under acute memory pressure. Add SWAP_FLAG_OFFLOAD_ONLY to

Add zram tests for proactive offload, fallback to conventional swap under ordinary pressure, zswap bypass, discard policy and data recovery after swapoff. Pin reclaim transitions to one CPU to exercis

Faulting and dirtying one page of a swapped-out large folio can leave sibling PTEs referring to its existing offload-only swap allocation. Exercise this path with zram behind dm-delay: ordinary reclai