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Re: [PATCH 9/15] Move alloc_pid() after the namespace is cloned [message #15437 is a reply to message #15303] Tue, 31 July 2007 05:49 Go to previous messageGo to previous message
Sukadev Bhattiprolu is currently offline  Sukadev Bhattiprolu
Messages: 413
Registered: August 2006
Senior Member
Pavel Emelianov [xemul@openvz.org] wrote:
| When we create new namespace we will need to allocate the struct pid,
| that will have one extra struct upid in array, comparing to the parent.
| Thus we need to know the new namespace (if any) in alloc_pid() to init
| this struct upid properly, so move the alloc_pid() call lower in
| copy_process().
|
| This is a fix for Sukadev's patch that moved the alloc_pid() call from
| do_fork() into copy_process().
|
| Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
|
| ---
|
| fork.c | 59 ++++++++++++++++++++++++++++++++++++++---------------------
| 1 files changed, 38 insertions(+), 21 deletions(-)
|
| diff -upr linux-2.6.23-rc1-mm1.orig/kernel/fork.c
| linux-2.6.23-rc1-mm1-7/kernel/fork.c
| --- linux-2.6.23-rc1-mm1.orig/kernel/fork.c 2007-07-26
| 16:34:45.000000000 +0400
| +++ linux-2.6.23-rc1-mm1-7/kernel/fork.c 2007-07-26
| 16:36:37.000000000 +0400
| @@ -1028,16 +1029,9 @@ 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);
| - p->pid = pid_nr(pid);
| INIT_LIST_HEAD(&p->children);
| INIT_LIST_HEAD(&p->sibling);
| p->vfork_done = NULL;
| @@ -1112,10 +1106,6 @@ static struct task_struct *copy_process(
| p->blocked_on = NULL; /* not blocked yet */
| #endif
|
| - p->tgid = p->pid;
| - if (clone_flags & CLONE_THREAD)
| - p->tgid = current->tgid;
| -
| if ((retval = security_task_alloc(p)))
| goto bad_fork_cleanup_policy;
| if ((retval = audit_alloc(p)))
| @@ -1141,6 +1131,17 @@ static struct task_struct *copy_process(
| if (retval)
| goto bad_fork_cleanup_namespaces;
|
| + if (pid != &init_struct_pid) {
| + pid = alloc_pid(task_active_pid_ns(p));
| + if (!pid)
| + goto bad_fork_cleanup_namespaces;

We should set retval to -EAGAIN before this goto. Otherwise, when we
take this goto, retval would be 0 (bc copy_thread() succeeded) and we
crash in the caller.


| + }
| +
| + p->pid = pid_nr(pid);
| + p->tgid = p->pid;
| + if (clone_flags & CLONE_THREAD)
| + p->tgid = current->tgid;
| +
| p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr
| : NULL;
| /*
| * Clear TID on mm_release()?
| @@ -1237,7 +1242,7 @@ static struct task_struct *copy_process(
| spin_unlock(&current->sighand->siglock);
| write_unlock_irq(&tasklist_lock);
| retval = -ERESTARTNOINTR;
| - goto bad_fork_cleanup_namespaces;
| + goto bad_fork_free_pid;
| }
|
| if (clone_flags & CLONE_THREAD) {
| @@ -1266,11 +1271,22 @@ static struct task_struct *copy_process(
| __ptrace_link(p, current->parent);
|
| if (thread_group_leader(p)) {
| - p->signal->tty = current->signal->tty;
| - p->signal->pgrp = task_pgrp_nr(current);
| - set_task_session(p, task_session_nr(current));
| - attach_pid(p, PIDTYPE_PGID, task_pgrp(current));
| - attach_pid(p, PIDTYPE_SID, task_session(current));
| + if (clone_flags & CLONE_NEWPID) {
| + p->nsproxy->pid_ns->child_reaper = p;
| + p->signal->tty = NULL;
| + p->signal->pgrp = p->pid;
| + set_task_session(p, p->pid);
| + attach_pid(p, PIDTYPE_PGID, pid);
| + attach_pid(p, PIDTYPE_SID, pid);
| + } else {
| + p->signal->tty = current->signal->tty;
| + p->signal->pgrp = task_pgrp_nr(current);
| + set_task_session(p,
| task_session_nr(current));
| + 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)++;
| @@ -1288,6 +1304,9 @@ static struct task_struct *copy_process(
| container_post_fork(p);
| return p;
|
| +bad_fork_free_pid:
| + if (pid != &init_struct_pid)
| + free_pid(pid);
| bad_fork_cleanup_namespaces:
| exit_task_namespaces(p);
| bad_fork_cleanup_keys:
| @@ -1322,9 +1341,6 @@ 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:
| @@ -1406,7 +1422,13 @@ long do_fork(unsigned long clone_flags,
| if (!IS_ERR(p)) {
| struct completion vfork;
|
| - nr = pid_nr(task_pid(p));
| + /*
| + * this is enough to call pid_nr_ns here, but this if
| + * improves optimisation of regular fork()
| + */
| + nr = (clone_flags & CLONE_NEWPID) ?
| + task_pid_nr_ns(p, current->nsproxy->pid_ns) :
| + task_pid_vnr(p);
|
| if (clone_flags & CLONE_VFORK) {
| p->vfork_done = &vfork;

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