sched/headers: Prepare for new header dependencies before moving code to <linux/sched...

[mirror_ubuntu-artful-kernel.git] / mm / mprotect.c

diff --git a/mm/mprotect.c b/mm/mprotect.c
index f9c07f54dd62d928187985554695c3c1117c75a7..848e946b08e58e31bf6482bd091338a43bb66fe1 100644 (file)
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -33,34 +33,6 @@
 
 #include "internal.h"
 
-/*
- * For a prot_numa update we only hold mmap_sem for read so there is a
- * potential race with faulting where a pmd was temporarily none. This
- * function checks for a transhuge pmd under the appropriate lock. It
- * returns a pte if it was successfully locked or NULL if it raced with
- * a transhuge insertion.
- */
-static pte_t *lock_pte_protection(struct vm_area_struct *vma, pmd_t *pmd,
-                       unsigned long addr, int prot_numa, spinlock_t **ptl)
-{
-       pte_t *pte;
-       spinlock_t *pmdl;
-
-       /* !prot_numa is protected by mmap_sem held for write */
-       if (!prot_numa)
-               return pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
-
-       pmdl = pmd_lock(vma->vm_mm, pmd);
-       if (unlikely(pmd_trans_huge(*pmd) || pmd_none(*pmd))) {
-               spin_unlock(pmdl);
-               return NULL;
-       }
-
-       pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, ptl);
-       spin_unlock(pmdl);
-       return pte;
-}
-
 static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                unsigned long addr, unsigned long end, pgprot_t newprot,
                int dirty_accountable, int prot_numa)
@@ -71,7 +43,21 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
        unsigned long pages = 0;
        int target_node = NUMA_NO_NODE;
 
-       pte = lock_pte_protection(vma, pmd, addr, prot_numa, &ptl);
+       /*
+        * Can be called with only the mmap_sem for reading by
+        * prot_numa so we must check the pmd isn't constantly
+        * changing from under us from pmd_none to pmd_trans_huge
+        * and/or the other way around.
+        */
+       if (pmd_trans_unstable(pmd))
+               return 0;
+
+       /*
+        * The pmd points to a regular pte so the pmd can't change
+        * from under us even if the mmap_sem is only hold for
+        * reading.
+        */
+       pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
        if (!pte)
                return 0;
 
@@ -113,7 +99,7 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
                        ptent = ptep_modify_prot_start(mm, addr, pte);
                        ptent = pte_modify(ptent, newprot);
                        if (preserve_write)
-                               ptent = pte_mkwrite(ptent);
+                               ptent = pte_mk_savedwrite(ptent);
 
                        /* Avoid taking write faults for known dirty pages */
                        if (dirty_accountable && pte_dirty(ptent) &&
@@ -177,8 +163,6 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
                if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) {
                        if (next - addr != HPAGE_PMD_SIZE) {
                                __split_huge_pmd(vma, pmd, addr, false, NULL);
-                               if (pmd_trans_unstable(pmd))
-                                       continue;
                        } else {
                                int nr_ptes = change_huge_pmd(vma, pmd, addr,
                                                newprot, prot_numa);