From be88632505026a6537e1fb080f7887d639db8bc4 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Wed, 7 Sep 2022 11:01:44 -0700 Subject: [PATCH] powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will move to use RCU instead of disabling local interrupts in fast-GUP. Using an IPI is the old-styled way of serializing against fast-GUP although it still works as expected now. And fast-GUP now fixed the potential race with THP collapse by checking whether PMD is changed or not. So IPI broadcast in radix pmd collapse flush is not necessary anymore. But it is still needed for hash TLB. Link: https://lkml.kernel.org/r/20220907180144.555485-2-shy828301@gmail.com Suggested-by: Aneesh Kumar K.V Signed-off-by: Yang Shi Acked-by: David Hildenbrand Acked-by: Peter Xu Cc: Christophe Leroy Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: John Hubbard Cc: "Kirill A. Shutemov" Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Signed-off-by: Andrew Morton --- arch/powerpc/mm/book3s64/radix_pgtable.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 698274109c91f..e712f80fe1892 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -937,15 +937,6 @@ pmd_t radix__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long addre pmd = *pmdp; pmd_clear(pmdp); - /* - * pmdp collapse_flush need to ensure that there are no parallel gup - * walk after this call. This is needed so that we can have stable - * page ref count when collapsing a page. We don't allow a collapse page - * if we have gup taken on the page. We can ensure that by sending IPI - * because gup walk happens with IRQ disabled. - */ - serialize_against_pte_lookup(vma->vm_mm); - radix__flush_tlb_collapsed_pmd(vma->vm_mm, address); return pmd; -- 2.39.5