[RFC][PATCH 3/7] VPIDs: fork modifications

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This patch changes forking procedure. Basically it adds a function
do_fork_pid() that alows forking task with predefined virtual pid.
Also it adds required vpid manipulations on fork().
Simple and straightforward.

--- ./kernel/fork.c.vpid_fork	2006-02-02 14:33:58.811003152 +0300
+++ ./kernel/fork.c	2006-02-02 14:41:40.806769120 +0300
@@ -871,7 +871,7 @@ static task_t *copy_process(unsigned lon
 				 unsigned long stack_size,
 				 int __user *parent_tidptr,
 				 int __user *child_tidptr,
-				 int pid)
+				 int pid, int vpid)
 {
 	int retval;
 	struct task_struct *p = NULL;
@@ -932,9 +932,11 @@ static task_t *copy_process(unsigned lon
 	p->did_exec = 0;
 	copy_flags(clone_flags, p);
 	p->pid = pid;
+	if (set_virt_pid(p, alloc_vpid(p->pid, vpid ? : -1)) < 0)
+		goto bad_fork_cleanup_module;
 	retval = -EFAULT;
 	if (clone_flags & CLONE_PARENT_SETTID)
-		if (put_user(p->pid, parent_tidptr))
+		if (put_user(virt_pid(p), parent_tidptr))
 			goto bad_fork_cleanup;
 
 	p->proc_dentry = NULL;
@@ -985,8 +987,13 @@ static task_t *copy_process(unsigned lon
 #endif
 
 	p->tgid = p->pid;
-	if (clone_flags & CLONE_THREAD)
+	set_virt_tgid(p, virt_pid(p));
+	set_virt_pgid(p, virt_pgid(current));
+	set_virt_sid(p, virt_sid(current));
+	if (clone_flags & CLONE_THREAD) {
 		p->tgid = current->tgid;
+		set_virt_tgid(p, virt_tgid(current));
+	}
 
 	if ((retval = security_task_alloc(p)))
 		goto bad_fork_cleanup_policy;
@@ -1181,6 +1188,9 @@ bad_fork_cleanup_cpuset:
 #endif
 	cpuset_exit(p);
 bad_fork_cleanup:
+	if (virt_pid(p) != p->pid && virt_pid(p) > 0)
+		free_vpid(virt_pid(p));
+bad_fork_cleanup_module:
 	if (p->binfmt)
 		module_put(p->binfmt->module);
 bad_fork_cleanup_put_domain:
@@ -1206,7 +1216,7 @@ task_t * __devinit fork_idle(int cpu)
 	task_t *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, 0, 0);
 	if (!task)
 		return ERR_PTR(-ENOMEM);
 	init_idle(task, cpu);
@@ -1236,12 +1246,12 @@ static inline int fork_traceflag (unsign
  * It copies the process, and if successful kick-starts
  * it and waits for it to finish using the VM if required.
  */
-long do_fork(unsigned long clone_flags,
+static long do_fork_pid(unsigned long clone_flags,
 	      unsigned long stack_start,
 	      struct pt_regs *regs,
 	      unsigned long stack_size,
 	      int __user *parent_tidptr,
-	      int __user *child_tidptr)
+	      int __user *child_tidptr, int vpid)
 {
 	struct task_struct *p;
 	int trace = 0;
@@ -1255,7 +1265,8 @@ 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, pid);
+	p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr,
+			child_tidptr, pid, vpid);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.
@@ -1298,6 +1309,17 @@ long do_fork(unsigned long clone_flags,
 	return pid;
 }
 
+long do_fork(unsigned long clone_flags,
+		unsigned long stack_start,
+		struct pt_regs *regs,
+		unsigned long stack_size,
+		int __user *parent_tidptr,
+		int __user *child_tidptr)
+{
+	return do_fork_pid(clone_flags, stack_start, regs, stack_size,
+			parent_tidptr, child_tidptr, 0);
+}
+
 #ifndef ARCH_MIN_MMSTRUCT_ALIGN
 #define ARCH_MIN_MMSTRUCT_ALIGN 0
 #endif
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