Changelog: v2: * Fix a WARN in the shmem THP swap path. Thanks Baolin, Yosry, and Barry for the report and the discussion on how to solve it. * Squash the two patches into one. RFC v1: https://lore.kernel.org/all/20240923231142.4155415-1-nphamcs@xxxxxxxxx/ The SWAP_MAP_SHMEM state was originally introduced in the commit aaa468653b4a ("swap_info: note SWAP_MAP_SHMEM"), to quickly determine if a swap entry belongs to shmem during swapoff. However, swapoff has since been rewritten drastically in the commit b56a2d8af914 ("mm: rid swapoff of quadratic complexity"). Now having swap count == SWAP_MAP_SHMEM value is basically the same as having swap count == 1, and swap_shmem_alloc() behaves analogously to swap_duplicate() This RFC proposes the removal of this state and the associated helper to simplify the state machine (both mentally and code-wise). We will also have an extra state/special value that can be repurposed (for swap entries that never gets re-duplicated). Another motivation is the new swap abstraction I am currently working on, that would allow for swap/zswap decoupling, swapoff optimization, etc. The fewer states and swap API functions there are, the simpler the conversion will be. Nhat Pham (1): swap: shmem: remove SWAP_MAP_SHMEM include/linux/swap.h | 16 ++++++++-------- mm/shmem.c | 2 +- mm/swapfile.c | 41 +++++++++++++++++++++-------------------- 3 files changed, 30 insertions(+), 29 deletions(-) base-commit: 391cad4424af8bb563e1504c5adaef0155b4abb6 -- 2.43.5
