[PATCH] mm: split page table lock

[pandora-kernel.git] / mm / mremap.c

diff --git a/mm/mremap.c b/mm/mremap.c
index 8de77b6..b535438 100644 (file)
--- 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)