attach_pid() with struct pid parameter

attach_pid() currently takes a pid_t and then uses find_pid() to find the
corresponding struct pid.  Sometimes we already have the struct pid.  We can
then skip find_pid() if attach_pid() were to take a struct pid parameter.

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Cedric Le Goater <clg@fr.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: <containers@lists.osdl.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/kernel/pid.c b/kernel/pid.c
index d3ad724afa83..d76f59326bd4 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -247,13 +247,16 @@ struct pid * fastcall find_pid(int nr)
 }
 EXPORT_SYMBOL_GPL(find_pid);
 
-int fastcall attach_pid(struct task_struct *task, enum pid_type type, int nr)
+/*
+ * attach_pid() must be called with the tasklist_lock write-held.
+ */
+int fastcall attach_pid(struct task_struct *task, enum pid_type type,
+		struct pid *pid)
 {
 	struct pid_link *link;
-	struct pid *pid;
 
 	link = &task->pids[type];
-	link->pid = pid = find_pid(nr);
+	link->pid = pid;
 	hlist_add_head_rcu(&link->node, &pid->tasks[type]);
 
 	return 0;