Re: [PATCH] mm/memory.c: Remove pte_sw_mkyoung()
From: Nicholas Piggin <npiggin@gmail.com>
Date: 2021-02-04 03:24:22
Also in:
linux-arch, linux-mips, linux-mm, lkml
Excerpts from Andrew Morton's message of February 4, 2021 10:46 am:
On Wed, 3 Feb 2021 10:19:44 +0000 (UTC) Christophe Leroy [off-list ref] wrote:quoted
Commit 83d116c53058 ("mm: fix double page fault on arm64 if PTE_AF is cleared") introduced arch_faults_on_old_pte() helper to identify platforms that don't set page access bit in HW and require a page fault to set it. Commit 44bf431b47b4 ("mm/memory.c: Add memory read privilege on page fault handling") added pte_sw_mkyoung() which is yet another way to manage platforms that don't set page access bit in HW and require a page fault to set it. Remove that pte_sw_mkyoung() helper and use the already existing arch_faults_on_old_pte() helper together with pte_mkyoung() instead.This conflicts with mm/memory.c changes in linux-next. In do_set_pte(). Please check my efforts:
I wanted to just get rid of it completely -- https://marc.info/?l=linux-mm&m=160860750115163&w=2 Waiting for MIPs to get that patch mentioned merged or nacked but as yet seems to be no response from maintainers. https://lore.kernel.org/linux-arch/20201019081257.32127-1-huangpei@loongson.cn/ (local) Thanks, Nick
quoted hunk ↗ jump to hunk
--- a/arch/mips/include/asm/pgtable.h~mm-memoryc-remove-pte_sw_mkyoung +++ a/arch/mips/include/asm/pgtable.h@@ -406,8 +406,6 @@ static inline pte_t pte_mkyoung(pte_t pt return pte; } -#define pte_sw_mkyoung pte_mkyoung - #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_HUGE; } --- a/include/linux/pgtable.h~mm-memoryc-remove-pte_sw_mkyoung +++ a/include/linux/pgtable.h@@ -424,22 +424,6 @@ static inline void ptep_set_wrprotect(st } #endif -/* - * On some architectures hardware does not set page access bit when accessing - * memory page, it is responsibilty of software setting this bit. It brings - * out extra page fault penalty to track page access bit. For optimization page - * access bit can be set during all page fault flow on these arches. - * To be differentiate with macro pte_mkyoung, this macro is used on platforms - * where software maintains page access bit. - */ -#ifndef pte_sw_mkyoung -static inline pte_t pte_sw_mkyoung(pte_t pte) -{ - return pte; -} -#define pte_sw_mkyoung pte_sw_mkyoung -#endif - #ifndef pte_savedwrite #define pte_savedwrite pte_write #endif --- a/mm/memory.c~mm-memoryc-remove-pte_sw_mkyoung +++ a/mm/memory.c@@ -2902,7 +2902,8 @@ static vm_fault_t wp_page_copy(struct vm } flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte)); entry = mk_pte(new_page, vma->vm_page_prot); - entry = pte_sw_mkyoung(entry); + if (arch_faults_on_old_pte()) + entry = pte_mkyoung(entry); entry = maybe_mkwrite(pte_mkdirty(entry), vma); /*@@ -3560,7 +3561,8 @@ static vm_fault_t do_anonymous_page(stru __SetPageUptodate(page); entry = mk_pte(page, vma->vm_page_prot); - entry = pte_sw_mkyoung(entry); + if (arch_faults_on_old_pte()) + entry = pte_mkyoung(entry); if (vma->vm_flags & VM_WRITE) entry = pte_mkwrite(pte_mkdirty(entry));@@ -3745,8 +3747,8 @@ void do_set_pte(struct vm_fault *vmf, st if (prefault && arch_wants_old_prefaulted_pte()) entry = pte_mkold(entry); - else - entry = pte_sw_mkyoung(entry); + else if (arch_faults_on_old_pte()) + entry = pte_mkyoung(entry); if (write) entry = maybe_mkwrite(pte_mkdirty(entry), vma);_