Quoting [EMAIL PROTECTED] ([EMAIL PROTECTED]):
> [PATCH 03/05]
>
> This patch uses the value written into the next_syscall_data proc file
> as a target upid nr for the next process to be created.
> The following syscalls have a new behavior if next_syscall_data is set:
> . fork()
> . vfork()
> . clone()
>
> In the current version, if the process belongs to nested namespaces, only
> the upper namespace level upid nr is allowed to be predefined, since there
> is not yet a way to take a snapshot of upid nrs at all namespaces levels.
>
> But this can easily be extended in the future.
>
> Signed-off-by: Nadia Derbey <[EMAIL PROTECTED]>
Acked-by: Serge Hallyn <[EMAIL PROTECTED]>
thanks,
-serge
>
> ---
> include/linux/next_syscall_data.h | 2
> kernel/fork.c | 5 -
> kernel/pid.c | 116
> +++++++++++++++++++++++++++++++-------
> 3 files changed, 102 insertions(+), 21 deletions(-)
>
> Index: linux-2.6.26-rc8-mm1/kernel/pid.c
> ===================================================================
> --- linux-2.6.26-rc8-mm1.orig/kernel/pid.c 2008-07-08 12:12:39.000000000
> +0200
> +++ linux-2.6.26-rc8-mm1/kernel/pid.c 2008-07-08 12:24:04.000000000 +0200
> @@ -122,6 +122,26 @@ static void free_pidmap(struct upid *upi
> atomic_inc(&map->nr_free);
> }
>
> +static inline int alloc_pidmap_page(struct pidmap *map)
> +{
> + if (unlikely(!map->page)) {
> + void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
> + /*
> + * Free the page if someone raced with us
> + * installing it:
> + */
> + spin_lock_irq(&pidmap_lock);
> + if (map->page)
> + kfree(page);
> + else
> + map->page = page;
> + spin_unlock_irq(&pidmap_lock);
> + if (unlikely(!map->page))
> + return -1;
> + }
> + return 0;
> +}
> +
> static int alloc_pidmap(struct pid_namespace *pid_ns)
> {
> int i, offset, max_scan, pid, last = pid_ns->last_pid;
> @@ -134,21 +154,8 @@ static int alloc_pidmap(struct pid_names
> map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
> max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset;
> for (i = 0; i <= max_scan; ++i) {
> - if (unlikely(!map->page)) {
> - void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
> - /*
> - * Free the page if someone raced with us
> - * installing it:
> - */
> - spin_lock_irq(&pidmap_lock);
> - if (map->page)
> - kfree(page);
> - else
> - map->page = page;
> - spin_unlock_irq(&pidmap_lock);
> - if (unlikely(!map->page))
> - break;
> - }
> + if (unlikely(alloc_pidmap_page(map)))
> + break;
> if (likely(atomic_read(&map->nr_free))) {
> do {
> if (!test_and_set_bit(offset, map->page)) {
> @@ -182,6 +189,33 @@ static int alloc_pidmap(struct pid_names
> return -1;
> }
>
> +/*
> + * Return 0 if successful (i.e. next_nr could be assigned as a upid nr).
> + * -errno else
> + */
> +static int alloc_fixed_pidmap(struct pid_namespace *pid_ns, int next_nr)
> +{
> + int offset;
> + struct pidmap *map;
> +
> + if (next_nr < RESERVED_PIDS || next_nr >= pid_max)
> + return -EINVAL;
> +
> + map = &pid_ns->pidmap[next_nr / BITS_PER_PAGE];
> +
> + if (unlikely(alloc_pidmap_page(map)))
> + return -ENOMEM;
> +
> + offset = next_nr & BITS_PER_PAGE_MASK;
> + if (test_and_set_bit(offset, map->page))
> + return -EBUSY;
> +
> + atomic_dec(&map->nr_free);
> + pid_ns->last_pid = max(pid_ns->last_pid, next_nr);
> +
> + return 0;
> +}
> +
> int next_pidmap(struct pid_namespace *pid_ns, int last)
> {
> int offset;
> @@ -239,6 +273,24 @@ void free_pid(struct pid *pid)
> call_rcu(&pid->rcu, delayed_put_pid);
> }
>
> +/*
> + * Sets a predefined upid nr for the process' upper namespace level
> + */
> +static int set_predefined_pid(struct pid_namespace *ns, struct pid *pid,
> + int next_nr)
> +{
> + int i = ns->level;
> + int rc;
> +
> + rc = alloc_fixed_pidmap(ns, next_nr);
> + if (rc < 0)
> + return rc;
> +
> + pid->numbers[i].nr = next_nr;
> + pid->numbers[i].ns = ns;
> + return 0;
> +}
> +
> struct pid *alloc_pid(struct pid_namespace *ns)
> {
> struct pid *pid;
> @@ -248,14 +300,41 @@ struct pid *alloc_pid(struct pid_namespa
> struct upid *upid;
>
> pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
> - if (!pid)
> + if (!pid) {
> + pid = ERR_PTR(-ENOMEM);
> goto out;
> + }
>
> tmp = ns;
> - for (i = ns->level; i >= 0; i--) {
> + i = ns->level;
> + if (unlikely(next_data_set(current))) {
> + /*
> + * There is a upid nr specified, use it instead of letting
> + * the kernel chose it for us.
> + */
> + int next_nr = get_next_data(current);
> + int rc;
> +
> + reset_next_syscall_data(current);
> + rc = set_predefined_pid(tmp, pid, next_nr);
> + if (rc < 0) {
> + pid = ERR_PTR(rc);
> + goto out_free;
> + }
> + /* Go up one level */
> + tmp = tmp->parent;
> + i--;
> + }
> +
> + /*
> + * Let the lower levels upid nrs be automatically allocated
> + */
> + for ( ; i >= 0; i--) {
> nr = alloc_pidmap(tmp);
> - if (nr < 0)
> + if (nr < 0) {
> + pid = ERR_PTR(-ENOMEM);
> goto out_free;
> + }
>
> pid->numbers[i].nr = nr;
> pid->numbers[i].ns = tmp;
> @@ -284,7 +363,6 @@ out_free:
> free_pidmap(pid->numbers + i);
>
> kmem_cache_free(ns->pid_cachep, pid);
> - pid = NULL;
> goto out;
> }
>
> Index: linux-2.6.26-rc8-mm1/kernel/fork.c
> ===================================================================
> --- linux-2.6.26-rc8-mm1.orig/kernel/fork.c 2008-07-08 12:12:39.000000000
> +0200
> +++ linux-2.6.26-rc8-mm1/kernel/fork.c 2008-07-08 12:22:47.000000000
> +0200
> @@ -1118,10 +1118,11 @@ static struct task_struct *copy_process(
> goto bad_fork_cleanup_io;
>
> if (pid != &init_struct_pid) {
> - retval = -ENOMEM;
> pid = alloc_pid(task_active_pid_ns(p));
> - if (!pid)
> + if (IS_ERR(pid)) {
> + retval = PTR_ERR(pid);
> goto bad_fork_cleanup_io;
> + }
>
> if (clone_flags & CLONE_NEWPID) {
> retval = pid_ns_prepare_proc(task_active_pid_ns(p));
> Index: linux-2.6.26-rc8-mm1/include/linux/next_syscall_data.h
> ===================================================================
> --- linux-2.6.26-rc8-mm1.orig/include/linux/next_syscall_data.h
> 2008-07-08 12:12:39.000000000 +0200
> +++ linux-2.6.26-rc8-mm1/include/linux/next_syscall_data.h 2008-07-08
> 12:22:47.000000000 +0200
> @@ -5,6 +5,7 @@
> * following is supported today:
> * . object creation with a predefined id
> * . for a sysv ipc object
> + * . for a process
> */
>
> #ifndef _LINUX_NEXT_SYSCALL_DATA_H
> @@ -18,6 +19,7 @@
> * For example, it can be used to pre-set the id of the object to be created
> * by next syscall. The following syscalls support this feature:
> * . msgget(), semget(), shmget()
> + * . fork(), vfork(), clone()
> */
> struct next_syscall_data {
> int ndata;
>
> --
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