mm/memory_failure: fix the missing pte_unmap() call

The paired pte_unmap() call is missing before the
dev_pagemap_mapping_shift() returns.  So fix it.

David says:
 "I guess this code never runs on 32bit / highmem, that's why we didn't
  notice so far".

[akpm@linux-foundation.org: cleanup]

Link: https://lkml.kernel.org/r/20210923122642.4999-1-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 41901c7..3e6449f 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -306,6 +306,7 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
                struct vm_area_struct *vma)
 {
        unsigned long address = vma_address(page, vma);
+       unsigned long ret = 0;
        pgd_t *pgd;
        p4d_t *p4d;
        pud_t *pud;
@@ -329,11 +330,10 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
        if (pmd_devmap(*pmd))
                return PMD_SHIFT;
        pte = pte_offset_map(pmd, address);
-       if (!pte_present(*pte))
-               return 0;
-       if (pte_devmap(*pte))
-               return PAGE_SHIFT;
-       return 0;
+       if (pte_present(*pte) && pte_devmap(*pte))
+               ret = PAGE_SHIFT;
+       pte_unmap(pte);
+       return ret;
 }
 
 /*