add poweroff command

hc

2023-12-14 982b8cc116118b3463d3f332581945625722acd8

 kernel/mm/huge_memory.c
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..
@@ -1994,7 +1994,7 @@
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 {
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 	struct mm_struct *mm = vma->vm_mm;
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 	pgtable_t pgtable;
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-	pmd_t _pmd;
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+	pmd_t _pmd, old_pmd;
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 	int i;
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 	/*
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@@ -2005,7 +2005,7 @@
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 	 *
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 	 * See Documentation/vm/mmu_notifier.rst
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 	 */
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-	pmdp_huge_clear_flush(vma, haddr, pmd);
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+	old_pmd = pmdp_huge_clear_flush(vma, haddr, pmd);
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2009
 
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 	pgtable = pgtable_trans_huge_withdraw(mm, pmd);
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 	pmd_populate(mm, &_pmd, pgtable);
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@@ -2014,6 +2014,8 @@
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 		pte_t *pte, entry;
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 		entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot);
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 		entry = pte_mkspecial(entry);
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+		if (pmd_uffd_wp(old_pmd))
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+			entry = pte_mkuffd_wp(entry);
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 		pte = pte_offset_map(&_pmd, haddr);
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 		VM_BUG_ON(!pte_none(*pte));
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 		set_pte_at(mm, haddr, pte, entry);
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@@ -2816,6 +2818,9 @@
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 	if (PageSwapCache(page))
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 		return;
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+	if (!list_empty(page_deferred_list(page)))
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+		return;
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+
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 	spin_lock_irqsave(&ds_queue->split_queue_lock, flags);
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 	if (list_empty(page_deferred_list(page))) {
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 		count_vm_event(THP_DEFERRED_SPLIT_PAGE);