uprobes: Turn add_utask() into get_utask()

Rename add_utask() into get_utask() and change it to allocate on
demand to simplify the caller. Like get_xol_area() it will have
more users.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 7e3e5c5..16e54d6 100644 (file)
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1290,23 +1290,18 @@ void uprobe_copy_process(struct task_struct *t)
 }
 
 /*
- * Allocate a uprobe_task object for the task.
- * Called when the thread hits a breakpoint for the first time.
+ * Allocate a uprobe_task object for the task if if necessary.
+ * Called when the thread hits a breakpoint.
  *
  * Returns:
  * - pointer to new uprobe_task on success
  * - NULL otherwise
  */
-static struct uprobe_task *add_utask(void)
+static struct uprobe_task *get_utask(void)
 {
-       struct uprobe_task *utask;
-
-       utask = kzalloc(sizeof *utask, GFP_KERNEL);
-       if (unlikely(!utask))
-               return NULL;
-
-       current->utask = utask;
-       return utask;
+       if (!current->utask)
+               current->utask = kzalloc(sizeof(struct uprobe_task), GFP_KERNEL);
+       return current->utask;
 }
 
 /* Prepare to single-step probed instruction out of line. */
@@ -1505,13 +1500,9 @@ static void handle_swbp(struct pt_regs *regs)
        if (unlikely(!test_bit(UPROBE_COPY_INSN, &uprobe->flags)))
                goto out;
 
-       utask = current->utask;
-       if (!utask) {
-               utask = add_utask();
-               /* Cannot allocate; re-execute the instruction. */
-               if (!utask)
-                       goto out;
-       }
+       utask = get_utask();
+       if (!utask)
+               goto out;       /* re-execute the instruction. */
 
        handler_chain(uprobe, regs);
        if (can_skip_sstep(uprobe, regs))