[Devel] [RFC][PATCH] Pass struct pid * to copy_process()

[Sukadev Bhattiprolu]

Modify copy_process() to take a struct pid * parameter instead of a pid_t.
This simplifies the code a bit and also avoids having to call find_pid()
to convert the pid_t to a struct pid.

From: Sukadev Bhattiprolu <sukadev at us.ibm.com>

Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
Cc: Cedric Le Goater <clg at fr.ibm.com>
Cc: Dave Hansen <haveblue at us.ibm.com>
Cc: Serge Hallyn <serue at us.ibm.com>
Cc: Eric Biederman <ebiederm at xmission.com>
Cc: containers at lists.osdl.org
---
 kernel/fork.c |   46 +++++++++++++++++++++++-----------------------
 1 files changed, 23 insertions(+), 23 deletions(-)

Index: lx26-20-rc2-mm1/kernel/fork.c
===================================================================
--- lx26-20-rc2-mm1.orig/kernel/fork.c	2007-01-15 18:05:50.079031592 -0800
+++ lx26-20-rc2-mm1/kernel/fork.c	2007-01-15 18:31:40.984258160 -0800
@@ -954,8 +954,9 @@ static struct task_struct *copy_process(
 					unsigned long stack_size,
 					int __user *parent_tidptr,
 					int __user *child_tidptr,
-					int pid)
+					struct pid *spid)
 {
+	int nr = pid_nr(spid);
 	int retval;
 	struct task_struct *p = NULL;
 
@@ -1021,7 +1022,7 @@ static struct task_struct *copy_process(
 	p->did_exec = 0;
 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
 	copy_flags(clone_flags, p);
-	p->pid = pid;
+	p->pid = nr;
 	retval = -EFAULT;
 	if (clone_flags & CLONE_PARENT_SETTID)
 		if (put_user(p->pid, parent_tidptr))
@@ -1239,27 +1240,25 @@ static struct task_struct *copy_process(
 		}
 	}
 
-	if (likely(p->pid)) {
-		add_parent(p);
-		if (unlikely(p->ptrace & PT_PTRACED))
-			__ptrace_link(p, current->parent);
-
-		if (thread_group_leader(p)) {
-			pid_t pgid = process_group(current);
-			pid_t sid = process_session(current);
-
-			p->signal->tty = current->signal->tty;
-			p->signal->pgrp = pgid;
-			set_signal_session(p->signal, sid);
-			attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
-			attach_pid(p, PIDTYPE_SID, task_session(current));
+	add_parent(p);
+	if (unlikely(p->ptrace & PT_PTRACED))
+		__ptrace_link(p, current->parent);
+
+	if (thread_group_leader(p)) {
+		pid_t pgid = process_group(current);
+		pid_t sid = process_session(current);
+
+		p->signal->tty = current->signal->tty;
+		p->signal->pgrp = pgid;
+		set_signal_session(p->signal, sid);
+		attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
+		attach_pid(p, PIDTYPE_SID, task_session(current));
 
-			list_add_tail_rcu(&p->tasks, &init_task.tasks);
-			__get_cpu_var(process_counts)++;
-		}
-		attach_pid(p, PIDTYPE_PID, find_pid(p->pid));
-		nr_threads++;
+		list_add_tail_rcu(&p->tasks, &init_task.tasks);
+		__get_cpu_var(process_counts)++;
 	}
+	attach_pid(p, PIDTYPE_PID, spid);
+	nr_threads++;
 
 	total_forks++;
 	spin_unlock(&current->sighand->siglock);
@@ -1321,7 +1320,8 @@ struct task_struct * __devinit fork_idle
 	struct task_struct *task;
 	struct pt_regs regs;
 
-	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL, 0);
+	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL,
+				&init_struct_pid);
 	if (!IS_ERR(task))
 		init_idle(task, cpu);
 
@@ -1371,7 +1371,7 @@ long do_fork(unsigned long clone_flags,
 			clone_flags |= CLONE_PTRACE;
 	}
 
-	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, nr);
+	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.
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