fork/exec: cleanup mm initialization

mm initialization on fork/exec is spread all over the place, which makes
the code look inconsistent.

We have mm_init(), which is supposed to init/nullify mm's internals, but
it doesn't init all the fields it should:

 - on fork ->mmap,mm_rb,vmacache_seqnum,map_count,mm_cpumask,locked_vm
   are zeroed in dup_mmap();

 - on fork ->pmd_huge_pte is zeroed in dup_mm(), immediately before
   calling mm_init();

 - ->cpu_vm_mask_var ptr is initialized by mm_init_cpumask(), which is
   called before mm_init() on both fork and exec;

 - ->context is initialized by init_new_context(), which is called after
   mm_init() on both fork and exec;

Let's consolidate all the initializations in mm_init() to make the code
look cleaner.

Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 27 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index f6f5086c9e7d..418b52a9ec6a 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -374,12 +374,6 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
          */
         down_write_nested(&mm->mmap_sem, SINGLE_DEPTH_NESTING);
 
-        mm->locked_vm = 0;
-        mm->mmap = NULL;
-        mm->vmacache_seqnum = 0;
-        mm->map_count = 0;
-        cpumask_clear(mm_cpumask(mm));
-        mm->mm_rb = RB_ROOT;
         rb_link = &mm->mm_rb.rb_node;
         rb_parent = NULL;
         pprev = &mm->mmap;
@@ -538,17 +532,27 @@ static void mm_init_aio(struct mm_struct *mm)
 
 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 {
+        mm->mmap = NULL;
+        mm->mm_rb = RB_ROOT;
+        mm->vmacache_seqnum = 0;
         atomic_set(&mm->mm_users, 1);
         atomic_set(&mm->mm_count, 1);
         init_rwsem(&mm->mmap_sem);
         INIT_LIST_HEAD(&mm->mmlist);
         mm->core_state = NULL;
         atomic_long_set(&mm->nr_ptes, 0);
+        mm->map_count = 0;
+        mm->locked_vm = 0;
         memset(&mm->rss_stat, 0, sizeof(mm->rss_stat));
         spin_lock_init(&mm->page_table_lock);
+        mm_init_cpumask(mm);
         mm_init_aio(mm);
         mm_init_owner(mm, p);
+        mmu_notifier_mm_init(mm);
         clear_tlb_flush_pending(mm);
+#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
+        mm->pmd_huge_pte = NULL;
+#endif
 
         if (current->mm) {
                 mm->flags = current->mm->flags & MMF_INIT_MASK;
@@ -558,11 +562,17 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
                 mm->def_flags = 0;
         }
 
-        if (likely(!mm_alloc_pgd(mm))) {
-                mmu_notifier_mm_init(mm);
-                return mm;
-        }
+        if (mm_alloc_pgd(mm))
+                goto fail_nopgd;
+
+        if (init_new_context(p, mm))
+                goto fail_nocontext;
 
+        return mm;
+
+fail_nocontext:
+        mm_free_pgd(mm);
+fail_nopgd:
         free_mm(mm);
         return NULL;
 }
@@ -596,7 +606,6 @@ struct mm_struct *mm_alloc(void)
                 return NULL;
 
         memset(mm, 0, sizeof(*mm));
-        mm_init_cpumask(mm);
         return mm_init(mm, current);
 }
 
@@ -828,17 +837,10 @@ static struct mm_struct *dup_mm(struct task_struct *tsk)
                 goto fail_nomem;
 
         memcpy(mm, oldmm, sizeof(*mm));
-        mm_init_cpumask(mm);
 
-#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
-        mm->pmd_huge_pte = NULL;
-#endif
         if (!mm_init(mm, tsk))
                 goto fail_nomem;
 
-        if (init_new_context(tsk, mm))
-                goto fail_nocontext;
-
         dup_mm_exe_file(oldmm, mm);
 
         err = dup_mmap(mm, oldmm);
@@ -860,15 +862,6 @@ free_pt:
 
 fail_nomem:
         return NULL;
-
-fail_nocontext:
-        /*
-         * If init_new_context() failed, we cannot use mmput() to free the mm
-         * because it calls destroy_context()
-         */
-        mm_free_pgd(mm);
-        free_mm(mm);
-        return NULL;
 }
 
 static int copy_mm(unsigned long clone_flags, struct task_struct *tsk)