Re: [PATCH 5/5] [V2] Move alloc_pid() to copy_process()

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[email protected] wrote:

Subject: [PATCH 5/5] Move alloc_pid call to copy_process

From: Sukadev Bhattiprolu <[email protected]>

Move alloc_pid() into copy_process(). This will keep all pid and pid
namespace code together and simplify error handling when we support
multiple pid namespaces.

I would add smth like this to the comment:

When a task creates a new pid namespace, its init (i.e. this task's
child) will have pids with extra info inside - the new numerical id,
that represent this new task in this new namespace. Thus, we have to allocate this new pid only after the namespace creation to find out which namespace this pid will live in.

Hope, I expressed my idea cleanly.

Acked-by: Pavel Emelyanov <[email protected]>

Signed-off-by: Sukadev Bhattiprolu <[email protected]>

Cc: Pavel Emelianov <[email protected]>
Cc: Eric W. Biederman <[email protected]>
Cc: Cedric Le Goater <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Herbert Poetzel <[email protected]>
---
 kernel/fork.c |   19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

Index: lx26-22-rc6-mm1a/kernel/fork.c
===================================================================
--- lx26-22-rc6-mm1a.orig/kernel/fork.c	2007-07-16 12:55:13.000000000 -0700
+++ lx26-22-rc6-mm1a/kernel/fork.c	2007-07-17 10:08:12.000000000 -0700
@@ -1029,6 +1029,12 @@ static struct task_struct *copy_process(
 	if (p->binfmt && !try_module_get(p->binfmt->module))
 		goto bad_fork_cleanup_put_domain;
+ if (pid != &init_struct_pid) {
+		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);
@@ -1316,6 +1322,9 @@ bad_fork_cleanup_container:
 #endif
 	container_exit(p, container_callbacks_done);
 	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:
@@ -1380,19 +1389,16 @@ long do_fork(unsigned long clone_flags,
 {
 	struct task_struct *p;
 	int trace = 0;
-	struct pid *pid = alloc_pid();
 	long nr;
- if (!pid)
-		return -EAGAIN;
-	nr = pid->nr;
 	if (unlikely(current->ptrace)) {
 		trace = fork_traceflag (clone_flags);
 		if (trace)
 			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, NULL);
 	/*
 	 * Do this prior waking up the new thread - the thread pointer
 	 * might get invalid after that point, if the thread exits quickly.
@@ -1400,6 +1406,8 @@ 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);
@@ -1433,7 +1441,6 @@ long do_fork(unsigned long clone_flags,
 			}
 		}
 	} else {
-		free_pid(pid);
 		nr = PTR_ERR(p);
 	}
 	return nr;


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