mm: remove gup_flags FOLL_WRITE games from __get_user_pages()

[profile/mobile/platform/kernel/linux-3.10-sc7730.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index f035122..c2ec754 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1469,6 +1469,16 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
 }
 EXPORT_SYMBOL_GPL(zap_vma_ptes);
 
+/*
+ * FOLL_FORCE can write to even unwritable pte's, but only
+ * after we've gone through a COW cycle and they are dirty.
+ */
+static inline bool can_follow_write_pte(pte_t pte, unsigned int flags)
+{
+       return pte_write(pte) ||
+               ((flags & FOLL_FORCE) && (flags & FOLL_COW) && pte_dirty(pte));
+}
+
 /**
  * follow_page_mask - look up a page descriptor from a user-virtual address
  * @vma: vm_area_struct mapping @address
@@ -1576,7 +1586,7 @@ split_fallthrough:
        }
        if ((flags & FOLL_NUMA) && pte_numa(pte))
                goto no_page;
-       if ((flags & FOLL_WRITE) && !pte_write(pte))
+       if ((flags & FOLL_WRITE) && !can_follow_write_pte(pte, flags))
                goto unlock;
 
        page = vm_normal_page(vma, address, pte);
@@ -1883,7 +1893,7 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 */
                                if ((ret & VM_FAULT_WRITE) &&
                                    !(vma->vm_flags & VM_WRITE))
-                                       foll_flags &= ~FOLL_WRITE;
+                                       foll_flags |= FOLL_COW;
 
                                cond_resched();
                        }