From: Peter Xu Subject: include/linux/swapops.h: remove stub for non_swap_entry() The stub for non_swap_entry() may not help much, because MAX_SWAPFILES has already contained all the information to decide whether a swap entry is real swap entry or pesudo ones (migrations, ...). There can be some performance influences on non_swap_entry() with below conditions all met: !CONFIG_MIGRATION && !CONFIG_MEMORY_FAILURE && !CONFIG_DEVICE_PRIVATE But that's definitely not the major config most machines will use, at the meantime it's already in a slow path of swap entry (being parsed from a swap pte), so IMHO it shouldn't be a major issue. Also according to the analysis from Alistair, somehow the stub didn't do the job right [1]. To make the code cleaner, let's drop the stub. [1] https://lore.kernel.org/lkml/8735ihbw6g.fsf@nvdebian.thelocal/ Note: the uffd-wp shmem & hugetlbfs series will need this patch to make sure swap entries work as expected with below config as spotted by Alistair: !CONFIG_MIGRATION && !CONFIG_MEMORY_FAILURE && !CONFIG_DEVICE_PRIVATE && CONFIG_PTE_MARKER (PS: this config should mostly never gonna happen, though, afaict..) Link: https://lkml.kernel.org/r/20220413191147.66645-1-peterx@redhat.com Signed-off-by: Peter Xu Reviewed-by: Alistair Popple Cc: Hugh Dickins Signed-off-by: Andrew Morton --- include/linux/swapops.h | 8 -------- 1 file changed, 8 deletions(-) --- a/include/linux/swapops.h~mm-remove-stub-for-non_swap_entry +++ a/include/linux/swapops.h @@ -414,18 +414,10 @@ static inline void num_poisoned_pages_in } #endif -#if defined(CONFIG_MEMORY_FAILURE) || defined(CONFIG_MIGRATION) || \ - defined(CONFIG_DEVICE_PRIVATE) static inline int non_swap_entry(swp_entry_t entry) { return swp_type(entry) >= MAX_SWAPFILES; } -#else -static inline int non_swap_entry(swp_entry_t entry) -{ - return 0; -} -#endif #endif /* CONFIG_MMU */ #endif /* _LINUX_SWAPOPS_H */ _