linux-kernel - [PATCH] x86/mm/hotplug: fix BUG

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Date:   Tue,  6 Jun 2017 13:35:12 -0400
From:   Jérôme Glisse <jglisse@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove

With commit af2cf278ef4f we no longer free pud so that we
do not have synchronize all pgd on hotremove/vfree. But the
new 5 level page table code re-added that code f2a6a705 and
thus we now trigger a BUG_ON() l128 in sync_global_pgds()

This patch remove free_pud() like in af2cf278ef4f

Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Logan Gunthorpe <logang@...tatee.com>
---
 arch/x86/mm/init_64.c | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index a8a9972..8cf7e99 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -772,24 +772,6 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud)
 	spin_unlock(&init_mm.page_table_lock);
 }
 
-static void __meminit free_pud_table(pud_t *pud_start, p4d_t *p4d)
-{
-	pud_t *pud;
-	int i;
-
-	for (i = 0; i < PTRS_PER_PUD; i++) {
-		pud = pud_start + i;
-		if (!pud_none(*pud))
-			return;
-	}
-
-	/* free a pud talbe */
-	free_pagetable(p4d_page(*p4d), 0);
-	spin_lock(&init_mm.page_table_lock);
-	p4d_clear(p4d);
-	spin_unlock(&init_mm.page_table_lock);
-}
-
 static void __meminit
 remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end,
 		 bool direct)
@@ -991,7 +973,6 @@ remove_p4d_table(p4d_t *p4d_start, unsigned long addr, unsigned long end,
 
 		pud_base = pud_offset(p4d, 0);
 		remove_pud_table(pud_base, addr, next, direct);
-		free_pud_table(pud_base, p4d);
 	}
 
 	if (direct)
-- 
2.9.3