+ loongarch-update-local-tlb-if-pte-entry-exists.patch added to mm-unstable branch

+ loongarch-update-local-tlb-if-pte-entry-exists.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: LoongArch: update local TLB if PTE entry exists
has been added to the -mm mm-unstable branch.  Its filename is
     loongarch-update-local-tlb-if-pte-entry-exists.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/loongarch-update-local-tlb-if-pte-entry-exists.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Qi Zheng <zhengqi.arch@bytedance.com>
Subject: LoongArch: update local TLB if PTE entry exists
Date: Thu, 29 Sep 2022 19:23:18 +0800

Currently, the implementation of update_mmu_tlb() is empty if
__HAVE_ARCH_UPDATE_MMU_TLB is not defined.  Then if two threads
concurrently fault at the same page, the second thread that did not win
the race will give up and do nothing.  In the LoongArch architecture, this
second thread will trigger another fault, and only updates its local TLB.

Instead of triggering another fault, it's better to implement
update_mmu_tlb() to directly update the local TLB of the second thread. 
Just do it.

Link: https://lkml.kernel.org/r/20220929112318.32393-3-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Suggested-by: Bibo Mao <maobibo@loongson.cn>
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Cc: Chris Zankel <chris@zankel.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/arch/loongarch/include/asm/pgtable.h~loongarch-update-local-tlb-if-pte-entry-exists
+++ a/arch/loongarch/include/asm/pgtable.h
@@ -412,6 +412,9 @@ static inline void update_mmu_cache(stru
 	__update_tlb(vma, address, ptep);
 }
 
+#define __HAVE_ARCH_UPDATE_MMU_TLB
+#define update_mmu_tlb	update_mmu_cache
+
 static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
 			unsigned long address, pmd_t *pmdp)
 {
_

Patches currently in -mm which might be from zhengqi.arch@bytedance.com are

mm-introduce-common-struct-mm_slot.patch
mm-thp-convert-to-use-common-struct-mm_slot.patch
ksm-remove-redundant-declarations-in-ksmh.patch
ksm-add-the-ksm-prefix-to-the-names-of-the-ksm-private-structures.patch
ksm-convert-ksm_mm_slotmm_list-to-ksm_mm_slotmm_node.patch
ksm-convert-ksm_mm_slotlink-to-ksm_mm_slothash.patch
ksm-convert-to-use-common-struct-mm_slot.patch
mm-use-update_mmu_tlb-on-the-second-thread.patch
loongarch-update-local-tlb-if-pte-entry-exists.patch