From 17b25a3801d11c28374a37cc672823cedb0f10d3 Mon Sep 17 00:00:00 2001
From: Hugh Dickins <hughd@google.com>
Date: Thu, 15 Jun 2023 16:02:43 -0700
Subject: [PATCH] mips: add pte_unmap() to balance pte_offset_map()

To keep balance in future, __update_tlb() remember to pte_unmap() after
pte_offset_map().  This is an odd case, since the caller has already done
pte_offset_map_lock(), then mips forgets the address and recalculates it;
but my two naive attempts to clean that up did more harm than good.

Link: https://lkml.kernel.org/r/addfcb3-b5f4-976e-e050-a2508e589cfe@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Greg Ungerer <gerg@linux-m68k.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: John David Anglin <dave.anglin@bell.net>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 arch/mips/mm/tlb-r4k.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/mips/mm/tlb-r4k.c b/arch/mips/mm/tlb-r4k.c
index 1b939ab..93c2d69 100644
--- a/arch/mips/mm/tlb-r4k.c
+++ b/arch/mips/mm/tlb-r4k.c
@@ -297,7 +297,7 @@ void __update_tlb(struct vm_area_struct * vma, unsigned long address, pte_t pte)
 	p4d_t *p4dp;
 	pud_t *pudp;
 	pmd_t *pmdp;
-	pte_t *ptep;
+	pte_t *ptep, *ptemap = NULL;
 	int idx, pid;
 
 	/*
@@ -344,7 +344,12 @@ void __update_tlb(struct vm_area_struct * vma, unsigned long address, pte_t pte)
 	} else
 #endif
 	{
-		ptep = pte_offset_map(pmdp, address);
+		ptemap = ptep = pte_offset_map(pmdp, address);
+		/*
+		 * update_mmu_cache() is called between pte_offset_map_lock()
+		 * and pte_unmap_unlock(), so we can assume that ptep is not
+		 * NULL here: and what should be done below if it were NULL?
+		 */
 
 #if defined(CONFIG_PHYS_ADDR_T_64BIT) && defined(CONFIG_CPU_MIPS32)
 #ifdef CONFIG_XPA
@@ -373,6 +378,9 @@ void __update_tlb(struct vm_area_struct * vma, unsigned long address, pte_t pte)
 	tlbw_use_hazard();
 	htw_start();
 	flush_micro_tlb_vm(vma);
+
+	if (ptemap)
+		pte_unmap(ptemap);
 	local_irq_restore(flags);
 }
 
-- 
2.7.4