[Devel] [RFC][PATCH 02/14] Move alloc_pid call to copy_process

[sukadev at us.ibm.com]

From: Sukadev Bhattiprolu <sukadev at us.ibm.com>
Subject: [RFC][PATCH 02/14] Move alloc_pid call to copy_process

Move alloc_pid() into copy_process(). This will help in
code to support cloning of pid namespace.

Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
---
 kernel/fork.c |   31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

Index: lx26-21-rc3-mm2/kernel/fork.c
===================================================================
--- lx26-21-rc3-mm2.orig/kernel/fork.c	2007-03-20 15:55:52.000000000 -0700
+++ lx26-21-rc3-mm2/kernel/fork.c	2007-03-20 20:17:05.000000000 -0700
@@ -952,6 +952,11 @@ static inline void rcu_task_init(struct 
 static inline void rcu_task_init(struct task_struct *p) {}
 #endif
 
+enum idle_process {
+	COPY_NON_IDLE_PROCESS,
+	COPY_IDLE_PROCESS,
+};
+
 /*
  * This creates a new process as a copy of the old one,
  * but does not actually start it yet.
@@ -966,10 +971,11 @@ static struct task_struct *copy_process(
 					unsigned long stack_size,
 					int __user *parent_tidptr,
 					int __user *child_tidptr,
-					struct pid *pid)
+					enum idle_process type)
 {
 	int retval;
 	struct task_struct *p = NULL;
+	struct pid *pid;
 
 	if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
 		return ERR_PTR(-EINVAL);
@@ -1030,6 +1036,13 @@ static struct task_struct *copy_process(
 	if (p->binfmt && !try_module_get(p->binfmt->module))
 		goto bad_fork_cleanup_put_domain;
 
+	if (unlikely(type == COPY_IDLE_PROCESS))
+		pid = &init_struct_pid;
+	else {
+		pid = alloc_pid();
+		if (!pid)
+			goto bad_fork_put_binfmt_module;
+	}
 	p->did_exec = 0;
 	delayacct_tsk_init(p);	/* Must remain after dup_task_struct() */
 	copy_flags(clone_flags, p);
@@ -1306,6 +1319,9 @@ bad_fork_cleanup_cpuset:
 #endif
 	cpuset_exit(p);
 	delayacct_tsk_free(p);
+	if (pid != &init_struct_pid)
+		free_pid(pid);
+bad_fork_put_binfmt_module:
 	if (p->binfmt)
 		module_put(p->binfmt->module);
 bad_fork_cleanup_put_domain:
@@ -1332,7 +1348,7 @@ struct task_struct * __cpuinit fork_idle
 	struct pt_regs regs;
 
 	task = copy_process(CLONE_VM, 0, idle_regs(&regs), 0, NULL, NULL,
-				&init_struct_pid);
+				COPY_IDLE_PROCESS);
 	if (!IS_ERR(task))
 		init_idle(task, cpu);
 
@@ -1353,14 +1369,10 @@ long do_fork(unsigned long clone_flags,
 	      int __user *child_tidptr)
 {
 	struct task_struct *p;
-	struct pid *pid = alloc_pid();
 	long nr;
 
-	if (!pid)
-		return -EAGAIN;
-	nr = pid->nr;
-
-	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid);
+	p = copy_process(clone_flags, stack_start, regs, stack_size,
+			parent_tidptr, child_tidptr, COPY_NON_IDLE_PROCESS);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.
@@ -1368,6 +1380,8 @@ long do_fork(unsigned long clone_flags,
 	if (!IS_ERR(p)) {
 		struct completion vfork;
 
+		nr = pid_nr(task_pid(p));
+
 		if (clone_flags & CLONE_VFORK) {
 			p->vfork_done = &vfork;
 			init_completion(&vfork);
@@ -1397,7 +1411,6 @@ long do_fork(unsigned long clone_flags,
 			tracehook_report_vfork_done(p, nr);
 		}
 	} else {
-		free_pid(pid);
 		nr = PTR_ERR(p);
 	}
 	return nr;
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