m: hugetlb: independent PMD page table shared count") Signed-off-by: David Hildenbrand (Red Hat) Reviewed-by: Rik van Riel Tested-by: Laurence Oberman Reviewed-by: Lorenzo Stoakes Acked-by: Oscar Salvador Reviewed-by: Harry Yoo Cc: Liu Shixin Cc: Lance Yang Cc: "Uschakow, Stanislav" Cc: Signed-off-by: Andrew Morton diff --git a/mm/hugetlb.c b/mm/hugetlb.c index e0ab14020513..67131aa24d77 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5320,17 +5320,10 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma, tlb_end_vma(tlb, vma); /* - * If we unshared PMDs, the TLB flush was not recorded in mmu_gather. We - * could defer the flush until now, since by holding i_mmap_rwsem we - * guaranteed that the last reference would not be dropped. But we must - * do the flushing before we return, as otherwise i_mmap_rwsem will be - * dropped and the last reference to the shared PMDs page might be - * dropped as well. - * - * In theory we could defer the freeing of the PMD pages as well, but - * huge_pmd_unshare() relies on the exact page_count for the PMD page to - * detect sharing, so we cannot defer the release of the page either. - * Instead, do flush now. + * There is nothing protecting a previously-shared page table that we + * unshared through huge_pmd_unshare() from getting freed after we + * release i_mmap_rwsem, so flush the TLB now. If huge_pmd_unshare() + * succeeded, flush the range corresponding to the pud. */ if (force_flush) tlb_flush_mmu_tlbonly(tlb); @@ -6552,11 +6545,10 @@ long hugetlb_change_protection(struct vm_area_struct *vma, cond_resched(); } /* - * Must flush TLB before releasing i_mmap_rwsem: x86's huge_pmd_unshare - * may have cleared our pud entry and done put_page on the page table: - * once we release i_mmap_rwsem, another task can do the final put_page - * and that page table be reused and filled with junk. If we actually - * did unshare a page of pmds, flush the range corresponding to the pud. + * There is nothing protecting a previously-shared page table that we + * unshared through huge_pmd_unshare() from getting freed after we + * release i_mmap_rwsem, so flush the TLB now. If huge_pmd_unshare() + * succeeded, flush the range corresponding to the pud. */ if (shared_pmd) flush_hugetlb_tlb_range(vma, range.start, range.end);FAILED: patch "[PATCH] mm/hugetlb: fix two comments related to huge_pmd_unshare()" failed to apply to 6.6-stable tree undefineddavid@kernel.org,akpm@linux-foundation.org,harry.yoo@oracle.com,lance.yang@linux.dev,liushixin2@huawei.com,loberman@redhat.com,lorenzo.stoakes@oracle.com,osalvador@suse.de,riel@surriel.com,stable@vger.kernel.org,suschako@amazon.de undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined undefined§R…¿S