KVM: x86: hardware task switching support

[deliverable/linux.git] / kernel / fork.c

diff --git a/kernel/fork.c b/kernel/fork.c
index 89fe414645e9b76aa777a0de7b5e9d6777814a0f..cb46befdd3a060bd3b6d96fc64acaadbf74c4e39 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -805,12 +805,6 @@ static int copy_files(unsigned long clone_flags, struct task_struct * tsk)
                goto out;
        }
 
-       /*
-        * Note: we may be using current for both targets (See exec.c)
-        * This works because we cache current->files (old) as oldf. Don't
-        * break this.
-        */
-       tsk->files = NULL;
        newf = dup_fd(oldf, &error);
        if (!newf)
                goto out;
@@ -846,34 +840,6 @@ static int copy_io(unsigned long clone_flags, struct task_struct *tsk)
        return 0;
 }
 
-/*
- *     Helper to unshare the files of the current task.
- *     We don't want to expose copy_files internals to
- *     the exec layer of the kernel.
- */
-
-int unshare_files(void)
-{
-       struct files_struct *files  = current->files;
-       int rc;
-
-       BUG_ON(!files);
-
-       /* This can race but the race causes us to copy when we don't
-          need to and drop the copy */
-       if(atomic_read(&files->count) == 1)
-       {
-               atomic_inc(&files->count);
-               return 0;
-       }
-       rc = copy_files(0, current);
-       if(rc)
-               current->files = files;
-       return rc;
-}
-
-EXPORT_SYMBOL(unshare_files);
-
 static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
 {
        struct sighand_struct *sig;
@@ -1811,3 +1777,27 @@ bad_unshare_cleanup_thread:
 bad_unshare_out:
        return err;
 }
+
+/*
+ *     Helper to unshare the files of the current task.
+ *     We don't want to expose copy_files internals to
+ *     the exec layer of the kernel.
+ */
+
+int unshare_files(struct files_struct **displaced)
+{
+       struct task_struct *task = current;
+       struct files_struct *copy = NULL;
+       int error;
+
+       error = unshare_fd(CLONE_FILES, &copy);
+       if (error || !copy) {
+               *displaced = NULL;
+               return error;
+       }
+       *displaced = task->files;
+       task_lock(task);
+       task->files = copy;
+       task_unlock(task);
+       return 0;
+}