From: Barry Song <v-songbaohua@oppo.com> mainline inclusion from mainline-v6.11-rc1 commit 259043e3b730e0aa6408bff27af7edf7a5c9101c category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IC3A3N Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- If CONFIG_ZSWAP is set to N, it means zswap cannot be enabled. zswap_never_enabled() should return true. The only effect of this issue is that with Barry's latest large folio swapin patches for zram ("mm: support mTHP swap-in for zRAM-like swapfile"), we will always fallback to order-0 swapin, even mistakenly when !CONFIG_ZSWAP. Basically this bug makes Barry's in progress patches not work at all. The API was created to inform the mm core that zswap has never been enabled, allowing the mm core to perform mTHP swap-in. This is a transitional solution until zswap supports mTHP. If zswap has been enabled, performing mTHP swap-in will result in corrupted data. You may find the answer in the mTHP swap-in series: https://lore.kernel.org/linux-mm/CAJD7tkZ4FQr6HZpduOdvmqgg_-whuZYE-Bz5O2t6yz... Link: https://lkml.kernel.org/r/20240629232231.42394-1-21cnbao@gmail.com Fixes: 0300e17d67c3 ("mm: zswap: add zswap_never_enabled()") Signed-off-by: Barry Song <v-songbaohua@oppo.com> Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev> Acked-by: Yosry Ahmed <yosryahmed@google.com> Acked-by: Chris Li <chrisl@kernel.org> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Nhat Pham <nphamcs@gmail.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Conflicts: include/linux/zswap.h [Context conflict.] Signed-off-by: Tong Tiangen <tongtiangen@huawei.com> --- include/linux/zswap.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/zswap.h b/include/linux/zswap.h index 4683a8fe0e5b..f647ee38598a 100644 --- a/include/linux/zswap.h +++ b/include/linux/zswap.h @@ -35,7 +35,7 @@ static inline void zswap_swapoff(int type) {} static inline bool zswap_never_enabled(void) { - return false; + return true; } #endif -- 2.25.1