[PATCH v2 12/23] powerpc: allow pte_offset_map[_lock]() to fail

[Hugh Dickins]

In rare transient cases, not yet made possible, pte_offset_map() and
pte_offset_map_lock() may not find a page table: handle appropriately.
Balance successful pte_offset_map() with pte_unmap() where omitted.

Signed-off-by: Hugh Dickins <hu...@google.com>
---
 arch/powerpc/mm/book3s64/hash_tlb.c     | 4 ++++
 arch/powerpc/mm/book3s64/subpage_prot.c | 2 ++
 arch/powerpc/xmon/xmon.c                | 5 ++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/book3s64/hash_tlb.c 
b/arch/powerpc/mm/book3s64/hash_tlb.c
index a64ea0a7ef96..21fcad97ae80 100644
--- a/arch/powerpc/mm/book3s64/hash_tlb.c
+++ b/arch/powerpc/mm/book3s64/hash_tlb.c
@@ -239,12 +239,16 @@ void flush_hash_table_pmd_range(struct mm_struct *mm, 
pmd_t *pmd, unsigned long
        local_irq_save(flags);
        arch_enter_lazy_mmu_mode();
        start_pte = pte_offset_map(pmd, addr);
+       if (!start_pte)
+               goto out;
        for (pte = start_pte; pte < start_pte + PTRS_PER_PTE; pte++) {
                unsigned long pteval = pte_val(*pte);
                if (pteval & H_PAGE_HASHPTE)
                        hpte_need_flush(mm, addr, pte, pteval, 0);
                addr += PAGE_SIZE;
        }
+       pte_unmap(start_pte);
+out:
        arch_leave_lazy_mmu_mode();
        local_irq_restore(flags);
 }
diff --git a/arch/powerpc/mm/book3s64/subpage_prot.c 
b/arch/powerpc/mm/book3s64/subpage_prot.c
index b75a9fb99599..0dc85556dec5 100644
--- a/arch/powerpc/mm/book3s64/subpage_prot.c
+++ b/arch/powerpc/mm/book3s64/subpage_prot.c
@@ -71,6 +71,8 @@ static void hpte_flush_range(struct mm_struct *mm, unsigned 
long addr,
        if (pmd_none(*pmd))
                return;
        pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+       if (!pte)
+               return;
        arch_enter_lazy_mmu_mode();
        for (; npages > 0; --npages) {
                pte_update(mm, addr, pte, 0, 0, 0);
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 70c4c59a1a8f..fae747cc57d2 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -3376,12 +3376,15 @@ static void show_pte(unsigned long addr)
        printf("pmdp @ 0x%px = 0x%016lx\n", pmdp, pmd_val(*pmdp));
 
        ptep = pte_offset_map(pmdp, addr);
-       if (pte_none(*ptep)) {
+       if (!ptep || pte_none(*ptep)) {
+               if (ptep)
+                       pte_unmap(ptep);
                printf("no valid PTE\n");
                return;
        }
 
        format_pte(ptep, pte_val(*ptep));
+       pte_unmap(ptep);
 
        sync();
        __delay(200);
-- 
2.35.3