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 of 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/ Cc: Alistair Popple <apopple@xxxxxxxxxx> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx> --- 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..) Quoting the same thread [1] as above. Please review, thanks. --- include/linux/swapops.h | 8 -------- 1 file changed, 8 deletions(-) diff --git a/include/linux/swapops.h b/include/linux/swapops.h index fffbba0036f6..a291f210e7f8 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -493,18 +493,10 @@ static inline void num_poisoned_pages_inc(void) } #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 */ -- 2.32.0
