mm: mempolicy: turn vma_set_policy() into vma_dup_policy()

Simple cleanup.  Every user of vma_set_policy() does the same work, this
looks a bit annoying imho.  And the new trivial helper which does
mpol_dup() + vma_set_policy() to simplify the callers.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 25 insertions, 20 deletions

diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index 0d7df39a5885..b2f897789838 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -91,7 +91,6 @@ static inline struct mempolicy *mpol_dup(struct mempolicy *pol)
 }
 
 #define vma_policy(vma) ((vma)->vm_policy)
-#define vma_set_policy(vma, pol) ((vma)->vm_policy = (pol))
 
 static inline void mpol_get(struct mempolicy *pol)
 {
@@ -126,6 +125,7 @@ struct shared_policy {
         spinlock_t lock;
 };
 
+int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst);
 void mpol_shared_policy_init(struct shared_policy *sp, struct mempolicy *mpol);
 int mpol_set_shared_policy(struct shared_policy *info,
                                 struct vm_area_struct *vma,
@@ -240,7 +240,12 @@ mpol_shared_policy_lookup(struct shared_policy *sp, unsigned long idx)
 }
 
 #define vma_policy(vma) NULL
-#define vma_set_policy(vma, pol) do {} while(0)
+
+static inline int
+vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
+{
+        return 0;
+}
 
 static inline void numa_policy_init(void)
 {
diff --git a/kernel/fork.c b/kernel/fork.c
index 84703db06cf3..81ccb4f010c2 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -351,7 +351,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
         struct rb_node **rb_link, *rb_parent;
         int retval;
         unsigned long charge;
-        struct mempolicy *pol;
 
         uprobe_start_dup_mmap();
         down_write(&oldmm->mmap_sem);
@@ -400,11 +399,9 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
                         goto fail_nomem;
                 *tmp = *mpnt;
                 INIT_LIST_HEAD(&tmp->anon_vma_chain);
-                pol = mpol_dup(vma_policy(mpnt));
-                retval = PTR_ERR(pol);
-                if (IS_ERR(pol))
+                retval = vma_dup_policy(mpnt, tmp);
+                if (retval)
                         goto fail_nomem_policy;
-                vma_set_policy(tmp, pol);
                 tmp->vm_mm = mm;
                 if (anon_vma_fork(tmp, mpnt))
                         goto fail_nomem_anon_vma_fork;
@@ -472,7 +469,7 @@ out:
         uprobe_end_dup_mmap();
         return retval;
 fail_nomem_anon_vma_fork:
-        mpol_put(pol);
+        mpol_put(vma_policy(tmp));
 fail_nomem_policy:
         kmem_cache_free(vm_area_cachep, tmp);
 fail_nomem:
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 4baf12e534d1..6b1d426731ae 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2065,6 +2065,16 @@ retry_cpuset:
 }
 EXPORT_SYMBOL(alloc_pages_current);
 
+int vma_dup_policy(struct vm_area_struct *src, struct vm_area_struct *dst)
+{
+        struct mempolicy *pol = mpol_dup(vma_policy(src));
+
+        if (IS_ERR(pol))
+                return PTR_ERR(pol);
+        dst->vm_policy = pol;
+        return 0;
+}
+
 /*
  * If mpol_dup() sees current->cpuset == cpuset_being_rebound, then it
  * rebinds the mempolicy its copying by calling mpol_rebind_policy()
diff --git a/mm/mmap.c b/mm/mmap.c
index f9c97d10b873..14f6bb4830f7 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2380,7 +2380,6 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
 static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
               unsigned long addr, int new_below)
 {
-        struct mempolicy *pol;
         struct vm_area_struct *new;
         int err = -ENOMEM;
 
@@ -2404,12 +2403,9 @@ static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
         }
 
-        pol = mpol_dup(vma_policy(vma));
-        if (IS_ERR(pol)) {
-                err = PTR_ERR(pol);
+        err = vma_dup_policy(vma, new);
+        if (err)
                 goto out_free_vma;
-        }
-        vma_set_policy(new, pol);
 
         if (anon_vma_clone(new, vma))
                 goto out_free_mpol;
@@ -2437,7 +2433,7 @@ static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma,
                 fput(new->vm_file);
         unlink_anon_vmas(new);
  out_free_mpol:
-        mpol_put(pol);
+        mpol_put(vma_policy(new));
  out_free_vma:
         kmem_cache_free(vm_area_cachep, new);
  out_err:
@@ -2780,7 +2776,6 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
         struct mm_struct *mm = vma->vm_mm;
         struct vm_area_struct *new_vma, *prev;
         struct rb_node **rb_link, *rb_parent;
-        struct mempolicy *pol;
         bool faulted_in_anon_vma = true;
 
         /*
@@ -2825,10 +2820,8 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
                         new_vma->vm_start = addr;
                         new_vma->vm_end = addr + len;
                         new_vma->vm_pgoff = pgoff;
-                        pol = mpol_dup(vma_policy(vma));
-                        if (IS_ERR(pol))
+                        if (vma_dup_policy(vma, new_vma))
                                 goto out_free_vma;
-                        vma_set_policy(new_vma, pol);
                         INIT_LIST_HEAD(&new_vma->anon_vma_chain);
                         if (anon_vma_clone(new_vma, vma))
                                 goto out_free_mempol;
@@ -2843,7 +2836,7 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
         return new_vma;
 
  out_free_mempol:
-        mpol_put(pol);
+        mpol_put(vma_policy(new_vma));
  out_free_vma:
         kmem_cache_free(vm_area_cachep, new_vma);
         return NULL;