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-rw-r--r--mm/mremap.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/mremap.c b/mm/mremap.c
index 8de77b6..b535438 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -72,7 +72,7 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
struct address_space *mapping = NULL;
struct mm_struct *mm = vma->vm_mm;
pte_t *old_pte, *new_pte, pte;
- spinlock_t *old_ptl;
+ spinlock_t *old_ptl, *new_ptl;
if (vma->vm_file) {
/*
@@ -88,8 +88,15 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
new_vma->vm_truncate_count = 0;
}
+ /*
+ * We don't have to worry about the ordering of src and dst
+ * pte locks because exclusive mmap_sem prevents deadlock.
+ */
old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
new_pte = pte_offset_map_nested(new_pmd, new_addr);
+ new_ptl = pte_lockptr(mm, new_pmd);
+ if (new_ptl != old_ptl)
+ spin_lock(new_ptl);
for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
new_pte++, new_addr += PAGE_SIZE) {
@@ -101,6 +108,8 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
set_pte_at(mm, new_addr, new_pte, pte);
}
+ if (new_ptl != old_ptl)
+ spin_unlock(new_ptl);
pte_unmap_nested(new_pte - 1);
pte_unmap_unlock(old_pte - 1, old_ptl);
if (mapping)