Pierre Peiffer wrote:

> This patch adds a new IPC_SETID command to the System V IPCs set of
> commands, which allows to change the ID of an existing IPC.
>
> This command can be used through the semctl/shmctl/msgctl API, with the new
> ID passed as the third argument for msgctl and shmctl (instead of a
> pointer) and through the fourth argument for semctl.
> 
> To be successful, the following rules must be respected:
> - the IPC exists
> - the user must be allowed to change the IPC attributes regarding the IPC
>   permissions.
> - the new ID must satisfy the ID computation rule.
> - the entry (in the kernel internal table of IPCs) corresponding to the new
>   ID must be free.

That's an interesting way to reset the ids of sysv ipcs during a restart (after 
a checkpoint) and we're looking for ways to do that among other things.

How does it fit openvz ? Is it something openvz could use ? 
 
thanks,

C.

> Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
> 
> ---
>  include/linux/ipc.h      |    9 +++----
>  ipc/msg.c                |   16 ++++++++++++
>  ipc/sem.c                |   15 +++++++++++
>  ipc/shm.c                |   36 ++++++++++++++++++++++++++++
>  ipc/util.c               |   60
> +++++++++++++++++++++++++++++++++++++++++++++++
>  ipc/util.h               |    1
>  security/selinux/hooks.c |    3 ++
>  7 files changed, 136 insertions(+), 4 deletions(-)
> 
> Index: b/include/linux/ipc.h
> ===================================================================
> --- a/include/linux/ipc.h
> +++ b/include/linux/ipc.h
> @@ -35,10 +35,11 @@ struct ipc_perm
>   * Control commands used with semctl, msgctl and shmctl
>   * see also specific commands in sem.h, msg.h and shm.h
>   */
> -#define IPC_RMID 0     /* remove resource */
> -#define IPC_SET  1     /* set ipc_perm options */
> -#define IPC_STAT 2     /* get ipc_perm options */
> -#define IPC_INFO 3     /* see ipcs */
> +#define IPC_RMID  0     /* remove resource */
> +#define IPC_SET   1     /* set ipc_perm options */
> +#define IPC_STAT  2     /* get ipc_perm options */
> +#define IPC_INFO  3     /* see ipcs */
> +#define IPC_SETID 4     /* set ipc ID */
> 
>  /*
>   * Version flags for semctl, msgctl, and shmctl commands
> Index: b/ipc/msg.c
> ===================================================================
> --- a/ipc/msg.c
> +++ b/ipc/msg.c
> @@ -491,6 +491,7 @@ asmlinkage long sys_msgctl(int msqid, in
>          if (copy_msqid_from_user(&setbuf, buf, version))
>              return -EFAULT;
>          break;
> +    case IPC_SETID:
>      case IPC_RMID:
>          break;
>      default:
> @@ -553,6 +554,21 @@ asmlinkage long sys_msgctl(int msqid, in
>          msg_unlock(msq);
>          break;
>      }
> +    case IPC_SETID:
> +    {
> +        int nid = (int)buf;
> +
> +        err = ipc_mvid(&msg_ids(ns), msq->q_id,
> +                   nid, ns->msg_ctlmni);
> +
> +        if (err)
> +            goto out_unlock_up;
> +
> +        msq->q_id = nid;
> +        msq->q_ctime = get_seconds();
> +        msg_unlock(msq);
> +        break;
> +    }
>      case IPC_RMID:
>          freeque(ns, msq, msqid);
>          break;
> Index: b/ipc/sem.c
> ===================================================================
> --- a/ipc/sem.c
> +++ b/ipc/sem.c
> @@ -908,6 +908,20 @@ static int semctl_down(struct ipc_namesp
>          sem_unlock(sma);
>          err = 0;
>          break;
> +    case IPC_SETID:
> +    {
> +        int nid = (int)arg.val;
> +        err = ipc_mvid(&sem_ids(ns), semid,
> +                   nid, ns->sc_semmni);
> +
> +        if (err)
> +            goto out_unlock;
> +
> +        sma->sem_id = nid;
> +        sma->sem_ctime = get_seconds();
> +        sem_unlock(sma);
> +        break;
> +    }
>      default:
>          sem_unlock(sma);
>          err = -EINVAL;
> @@ -950,6 +964,7 @@ asmlinkage long sys_semctl (int semid, i
>          return err;
>      case IPC_RMID:
>      case IPC_SET:
> +    case IPC_SETID:
>          mutex_lock(&sem_ids(ns).mutex);
>          err = semctl_down(ns,semid,semnum,cmd,version,arg);
>          mutex_unlock(&sem_ids(ns).mutex);
> Index: b/ipc/util.c
> ===================================================================
> --- a/ipc/util.c
> +++ b/ipc/util.c
> @@ -327,6 +327,66 @@ found:
>  }
> 
>  /**
> + *    ipc_mvid     -    move an IPC identifier
> + *    @ids: IPC identifier set
> + *    @oldid: ID of the IPC permission set to move
> + *    @newid: new ID of the IPC permission set to move
> + *    @size: new size limit for the id array
> + *
> + *    Move an entry in the IPC arrays from the 'oldid' place to the
> + *      'newid' place. The seq number of the entry is updated to match the
> + *      'newid' value.
> + *
> + *    Called with the list lock and ipc_ids.mutex held.
> + */
> +
> +int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size)
> +{
> +    struct kern_ipc_perm *p;
> +    int old_lid = oldid % SEQ_MULTIPLIER;
> +    int new_lid = newid % SEQ_MULTIPLIER;
> +
> +    if ((new_lid >= size) ||
> +        newid !=  (new_lid + (newid/SEQ_MULTIPLIER)*SEQ_MULTIPLIER))
> +        return -ERANGE;
> +
> +    size = grow_ary(ids,size);
> +
> +    BUG_ON(old_lid >= ids->entries->size);
> +
> +    p = ids->entries->p[old_lid];
> +
> +    if (!p)
> +        return -ENXIO;
> +
> +    /*
> +     * The id (n° of the entry in the table entries) may be the same
> +     * but not the seq number.
> +     */
> +    if (new_lid != old_lid) {
> +
> +        if (ids->entries->p[new_lid])
> +            return -EBUSY;
> +
> +        ids->entries->p[new_lid] = p;
> +
> +        ids->entries->p[old_lid] = NULL;
> +
> +        if (new_lid > ids->max_id)
> +            ids->max_id = new_lid;
> +        if (old_lid == ids->max_id) {
> +            do {
> +                --old_lid;
> +            } while (ids->entries->p[old_lid] == NULL);
> +            ids->max_id = old_lid;
> +        }
> +    }
> +
> +    p->seq = newid/SEQ_MULTIPLIER;
> +    return 0;
> +}
> +
> +/**
>   *    ipc_rmid    -    remove an IPC identifier
>   *    @ids: identifier set
>   *    @id: Identifier to remove
> Index: b/ipc/util.h
> ===================================================================
> --- a/ipc/util.h
> +++ b/ipc/util.h
> @@ -63,6 +63,7 @@ int ipc_findkey(struct ipc_ids* ids, key
>  int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size);
> 
>  /* must be called with both locks acquired. */
> +int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size);
>  struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id);
> 
>  int ipcperms (struct kern_ipc_perm *ipcp, short flg);
> Index: b/security/selinux/hooks.c
> ===================================================================
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -4152,6 +4152,7 @@ static int selinux_msg_queue_msgctl(stru
>          perms = MSGQ__GETATTR | MSGQ__ASSOCIATE;
>          break;
>      case IPC_SET:
> +    case IPC_SETID:
>          perms = MSGQ__SETATTR;
>          break;
>      case IPC_RMID:
> @@ -4300,6 +4301,7 @@ static int selinux_shm_shmctl(struct shm
>          perms = SHM__GETATTR | SHM__ASSOCIATE;
>          break;
>      case IPC_SET:
> +    case IPC_SETID:
>          perms = SHM__SETATTR;
>          break;
>      case SHM_LOCK:
> @@ -4411,6 +4413,7 @@ static int selinux_sem_semctl(struct sem
>          perms = SEM__DESTROY;
>          break;
>      case IPC_SET:
> +    case IPC_SETID:
>          perms = SEM__SETATTR;
>          break;
>      case IPC_STAT:
> Index: b/ipc/shm.c
> ===================================================================
> --- a/ipc/shm.c
> +++ b/ipc/shm.c
> @@ -809,6 +809,42 @@ asmlinkage long sys_shmctl (int shmid, i
>          break;
>      }
> 
> +    case IPC_SETID:
> +    {
> +        int nid = (int)buf;
> +        mutex_lock(&shm_ids(ns).mutex);
> +        shp = shm_lock(ns, shmid);
> +        err = -EINVAL;
> +        if(shp == NULL)
> +            goto out_up;
> +        err = shm_checkid(ns, shp,shmid);
> +        if(err)
> +            goto out_unlock_up;
> +        err = audit_ipc_obj(&(shp->shm_perm));
> +        if (err)
> +            goto out_unlock_up;
> +
> +        err = -EPERM;
> +        if (current->euid != shp->shm_perm.uid &&
> +            current->euid != shp->shm_perm.cuid &&
> +            !capable(CAP_SYS_ADMIN))
> +            goto out_unlock_up;
> +
> +        err = security_shm_shmctl(shp, cmd);
> +        if (err)
> +            goto out_unlock_up;
> +
> +        err = ipc_mvid(&shm_ids(ns), shp->id,
> +                   nid, ns->shm_ctlmni);
> +
> +        if (err)
> +            goto out_unlock_up;
> +
> +        shp->id = nid;
> +        shp->shm_ctim = get_seconds();
> +        break;
> +    }
> +
>      default:
>          err = -EINVAL;
>          goto out;
> 

_______________________________________________
Containers mailing list
Containers@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers

Kirill Korotaev wrote:
> Cedric Le Goater wrote:
>> Pierre Peiffer wrote:
>>
>>
>>> This patch adds a new IPC_SETID command to the System V IPCs set of
>>> commands, which allows to change the ID of an existing IPC.
>>>
>>> This command can be used through the semctl/shmctl/msgctl API, with the new
>>> ID passed as the third argument for msgctl and shmctl (instead of a
>>> pointer) and through the fourth argument for semctl.
>>>
>>> To be successful, the following rules must be respected:
>>> - the IPC exists
>>> - the user must be allowed to change the IPC attributes regarding the IPC
>>>  permissions.
>>> - the new ID must satisfy the ID computation rule.
>>> - the entry (in the kernel internal table of IPCs) corresponding to the new
>>>  ID must be free.
>>
>> That's an interesting way to reset the ids of sysv ipcs during a restart (after 
>> a checkpoint) and we're looking for ways to do that among other things.
>>
>> How does it fit openvz ? Is it something openvz could use ? 
> 
> my personal imho is that we should not export such interfaces to user space
> and do the checkpointing from the kernel.
> 
> it simplifies a lot of things and makes checkpointing more elegant.
> So until there is some user-space usage scenario of the patch I missed -
> i wouldn't commit it.

Hi Kirill,

I have no particular preference about checkpointing from userspace or 
kernelspace. Can you explain why doing the checkpoint from kernel 
simplifies the problem ? Do you have some examples about resources 
checkpointed from kernel which make the job easier ?

I thought we can divide system into subsystem and use the generic 
netlink to define a family for each subsystem. The result will be a 
checkpoint orchestrated from userspace but checkpointed from kernel.

   -- Daniel

_______________________________________________
Containers mailing list
Containers@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers

Cedric Le Goater wrote:
> Pierre Peiffer wrote:
> 
> 
>>This patch adds a new IPC_SETID command to the System V IPCs set of
>>commands, which allows to change the ID of an existing IPC.
>>
>>This command can be used through the semctl/shmctl/msgctl API, with the new
>>ID passed as the third argument for msgctl and shmctl (instead of a
>>pointer) and through the fourth argument for semctl.
>>
>>To be successful, the following rules must be respected:
>>- the IPC exists
>>- the user must be allowed to change the IPC attributes regarding the IPC
>>  permissions.
>>- the new ID must satisfy the ID computation rule.
>>- the entry (in the kernel internal table of IPCs) corresponding to the new
>>  ID must be free.
> 
> 
> That's an interesting way to reset the ids of sysv ipcs during a restart (after 
> a checkpoint) and we're looking for ways to do that among other things.
> 
> How does it fit openvz ? Is it something openvz could use ? 

my personal imho is that we should not export such interfaces to user space
and do the checkpointing from the kernel.

it simplifies a lot of things and makes checkpointing more elegant.
So until there is some user-space usage scenario of the patch I missed -
i wouldn't commit it.

Thanks,
Kirill

>  
> thanks,
> 
> C.
> 
> 
>>Signed-off-by: Pierre Peiffer <pierre.peiffer@bull.net>
>>
>>---
>> include/linux/ipc.h      |    9 +++----
>> ipc/msg.c                |   16 ++++++++++++
>> ipc/sem.c                |   15 +++++++++++
>> ipc/shm.c                |   36 ++++++++++++++++++++++++++++
>> ipc/util.c               |   60
>>+++++++++++++++++++++++++++++++++++++++++++++++
>> ipc/util.h               |    1
>> security/selinux/hooks.c |    3 ++
>> 7 files changed, 136 insertions(+), 4 deletions(-)
>>
>>Index: b/include/linux/ipc.h
>>===================================================================
>>--- a/include/linux/ipc.h
>>+++ b/include/linux/ipc.h
>>@@ -35,10 +35,11 @@ struct ipc_perm
>>  * Control commands used with semctl, msgctl and shmctl
>>  * see also specific commands in sem.h, msg.h and shm.h
>>  */
>>-#define IPC_RMID 0     /* remove resource */
>>-#define IPC_SET  1     /* set ipc_perm options */
>>-#define IPC_STAT 2     /* get ipc_perm options */
>>-#define IPC_INFO 3     /* see ipcs */
>>+#define IPC_RMID  0     /* remove resource */
>>+#define IPC_SET   1     /* set ipc_perm options */
>>+#define IPC_STAT  2     /* get ipc_perm options */
>>+#define IPC_INFO  3     /* see ipcs */
>>+#define IPC_SETID 4     /* set ipc ID */
>>
>> /*
>>  * Version flags for semctl, msgctl, and shmctl commands
>>Index: b/ipc/msg.c
>>===================================================================
>>--- a/ipc/msg.c
>>+++ b/ipc/msg.c
>>@@ -491,6 +491,7 @@ asmlinkage long sys_msgctl(int msqid, in
>>         if (copy_msqid_from_user(&setbuf, buf, version))
>>             return -EFAULT;
>>         break;
>>+    case IPC_SETID:
>>     case IPC_RMID:
>>         break;
>>     default:
>>@@ -553,6 +554,21 @@ asmlinkage long sys_msgctl(int msqid, in
>>         msg_unlock(msq);
>>         break;
>>     }
>>+    case IPC_SETID:
>>+    {
>>+        int nid = (int)buf;
>>+
>>+        err = ipc_mvid(&msg_ids(ns), msq->q_id,
>>+                   nid, ns->msg_ctlmni);
>>+
>>+        if (err)
>>+            goto out_unlock_up;
>>+
>>+        msq->q_id = nid;
>>+        msq->q_ctime = get_seconds();
>>+        msg_unlock(msq);
>>+        break;
>>+    }
>>     case IPC_RMID:
>>         freeque(ns, msq, msqid);
>>         break;
>>Index: b/ipc/sem.c
>>===================================================================
>>--- a/ipc/sem.c
>>+++ b/ipc/sem.c
>>@@ -908,6 +908,20 @@ static int semctl_down(struct ipc_namesp
>>         sem_unlock(sma);
>>         err = 0;
>>         break;
>>+    case IPC_SETID:
>>+    {
>>+        int nid = (int)arg.val;
>>+        err = ipc_mvid(&sem_ids(ns), semid,
>>+                   nid, ns->sc_semmni);
>>+
>>+        if (err)
>>+            goto out_unlock;
>>+
>>+        sma->sem_id = nid;
>>+        sma->sem_ctime = get_seconds();
>>+        sem_unlock(sma);
>>+        break;
>>+    }
>>     default:
>>         sem_unlock(sma);
>>         err = -EINVAL;
>>@@ -950,6 +964,7 @@ asmlinkage long sys_semctl (int semid, i
>>         return err;
>>     case IPC_RMID:
>>     case IPC_SET:
>>+    case IPC_SETID:
>>         mutex_lock(&sem_ids(ns).mutex);
>>         err = semctl_down(ns,semid,semnum,cmd,version,arg);
>>         mutex_unlock(&sem_ids(ns).mutex);
>>Index: b/ipc/util.c
>>===================================================================
>>--- a/ipc/util.c
>>+++ b/ipc/util.c
>>@@ -327,6 +327,66 @@ found:
>> }
>>
>> /**
>>+ *    ipc_mvid     -    move an IPC identifier
>>+ *    @ids: IPC identifier set
>>+ *    @oldid: ID of the IPC permission set to move
>>+ *    @newid: new ID of the IPC permission set to move
>>+ *    @size: new size limit for the id array
>>+ *
>>+ *    Move an entry in the IPC arrays from the 'oldid' place to the
>>+ *      'newid' place. The seq number of the entry is updated to match the
>>+ *      'newid' value.
>>+ *
>>+ *    Called with the list lock and ipc_ids.mutex held.
>>+ */
>>+
>>+int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size)
>>+{
>>+    struct kern_ipc_perm *p;
>>+    int old_lid = oldid % SEQ_MULTIPLIER;
>>+    int new_lid = newid % SEQ_MULTIPLIER;
>>+
>>+    if ((new_lid >= size) ||
>>+        newid !=  (new_lid + (newid/SEQ_MULTIPLIER)*SEQ_MULTIPLIER))
>>+        return -ERANGE;
>>+
>>+    size = grow_ary(ids,size);
>>+
>>+    BUG_ON(old_lid >= ids->entries->size);
>>+
>>+    p = ids->entries->p[old_lid];
>>+
>>+    if (!p)
>>+        return -ENXIO;
>>+
>>+    /*
>>+     * The id (n° of the entry in the table entries) may be the same
>>+     * but not the seq number.
>>+     */
>>+    if (new_lid != old_lid) {
>>+
>>+        if (ids->entries->p[new_lid])
>>+            return -EBUSY;
>>+
>>+        ids->entries->p[new_lid] = p;
>>+
>>+        ids->entries->p[old_lid] = NULL;
>>+
>>+        if (new_lid > ids->max_id)
>>+            ids->max_id = new_lid;
>>+        if (old_lid == ids->max_id) {
>>+            do {
>>+                --old_lid;
>>+            } while (ids->entries->p[old_lid] == NULL);
>>+            ids->max_id = old_lid;
>>+        }
>>+    }
>>+
>>+    p->seq = newid/SEQ_MULTIPLIER;
>>+    return 0;
>>+}
>>+
>>+/**
>>  *    ipc_rmid    -    remove an IPC identifier
>>  *    @ids: identifier set
>>  *    @id: Identifier to remove
>>Index: b/ipc/util.h
>>===================================================================
>>--- a/ipc/util.h
>>+++ b/ipc/util.h
>>@@ -63,6 +63,7 @@ int ipc_findkey(struct ipc_ids* ids, key
>> int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size);
>>
>> /* must be called with both locks acquired. */
>>+int ipc_mvid(struct ipc_ids *ids, int oldid, int newid, int size);
>> struct kern_ipc_perm* ipc_rmid(struct ipc_ids* ids, int id);
>>
>> int ipcperms (struct kern_ipc_perm *ipcp, short flg);
>>Index: b/security/selinux/hooks.c
>>===================================================================
>>--- a/security/selinux/hooks.c
>>+++ b/security/selinux/hooks.c
>>@@ -4152,6 +4152,7 @@ static int selinux_msg_queue_msgctl(stru
>>         perms = MSGQ__GETATTR | MSGQ__ASSOCIATE;
>>         break;
>>     case IPC_SET:
>>+    case IPC_SETID:
>>         perms = MSGQ__SETATTR;
>>         break;
>>     case IPC_RMID:
>>@@ -4300,6 +4301,7 @@ static int selinux_shm_shmctl(struct shm
>>         perms = SHM__GETATTR | SHM__ASSOCIATE;
>>         break;
>>     case IPC_SET:
>>+    case IPC_SETID:
>>         perms = SHM__SETATTR;
>>         break;
>>     case SHM_LOCK:
>>@@ -4411,6 +4413,7 @@ static int selinux_sem_semctl(struct sem
>>         perms = SEM__DESTROY;
>>         break;
>>     case IPC_SET:
>>+    case IPC_SETID:
>>         perms = SEM__SETATTR;
>>         break;
>>     case IPC_STAT:
>>Index: b/ipc/shm.c
>>===================================================================
>>--- a/ipc/shm.c
>>+++ b/ipc/shm.c
>>@@ -809,6 +809,42 @@ asmlinkage long sys_shmctl (int shmid, i
>>         break;
>>     }
>>
>>+    case IPC_SETID:
>>+    {
>>+        int nid = (int)buf;
>>+        mutex_lock(&shm_ids(ns).mutex);
>>+        shp = shm_lock(ns, shmid);
>>+        err = -EINVAL;
>>+        if(shp == NULL)
>>+            goto out_up;
>>+        err = shm_checkid(ns, shp,shmid);
&g

Kirill Korotaev wrote:
> Cedric Le Goater wrote:
>> Pierre Peiffer wrote:
>>
>>
>>> This patch adds a new IPC_SETID command to the System V IPCs set of
>>> commands, which allows to change the ID of an existing IPC.
>>>
>>> This command can be used through the semctl/shmctl/msgctl API, with the new
>>> ID passed as the third argument for msgctl and shmctl (instead of a
>>> pointer) and through the fourth argument for semctl.
>>>
>>> To be successful, the following rules must be respected:
>>> - the IPC exists
>>> - the user must be allowed to change the IPC attributes regarding the IPC
>>>  permissions.
>>> - the new ID must satisfy the ID computation rule.
>>> - the entry (in the kernel internal table of IPCs) corresponding to the new
>>>  ID must be free.
>>
>> That's an interesting way to reset the ids of sysv ipcs during a restart (after 
>> a checkpoint) and we're looking for ways to do that among other things.
>>
>> How does it fit openvz ? Is it something openvz could use ? 
> 
> my personal imho is that we should not export such interfaces to user space
> and do the checkpointing from the kernel.
> it simplifies a lot of things and makes checkpointing more elegant.

I agree that we should not export useless interface to user but even
without exporting anything we need support from the kernel internals
(sysvipc in that case) to allow checkpointing. like setting the id. 
right ? 

so there might be some common ground with some new user space interface.
That's what we are looking for.

> So until there is some user-space usage scenario of the patch I missed -
> i wouldn't commit it.

Pierre has a user space tool to use it. quite simple. 

C.
_______________________________________________
Containers mailing list
Containers@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers

Quoting Cedric Le Goater (clg@fr.ibm.com):
> Kirill Korotaev wrote:
> > Cedric Le Goater wrote:
> >> Pierre Peiffer wrote:
> >>
> >>
> >>> This patch adds a new IPC_SETID command to the System V IPCs set of
> >>> commands, which allows to change the ID of an existing IPC.
> >>>
> >>> This command can be used through the semctl/shmctl/msgctl API, with the new
> >>> ID passed as the third argument for msgctl and shmctl (instead of a
> >>> pointer) and through the fourth argument for semctl.
> >>>
> >>> To be successful, the following rules must be respected:
> >>> - the IPC exists
> >>> - the user must be allowed to change the IPC attributes regarding the IPC
> >>>  permissions.
> >>> - the new ID must satisfy the ID computation rule.
> >>> - the entry (in the kernel internal table of IPCs) corresponding to the new
> >>>  ID must be free.
> >>
> >> That's an interesting way to reset the ids of sysv ipcs during a restart (after 
> >> a checkpoint) and we're looking for ways to do that among other things.
> >>
> >> How does it fit openvz ? Is it something openvz could use ? 
> > 
> > my personal imho is that we should not export such interfaces to user space
> > and do the checkpointing from the kernel.
> > it simplifies a lot of things and makes checkpointing more elegant.

You say more elegant, someone else might say less flexible and more
kernel version dependant.

I guess we can discuss this more at the bof next thursday, but this
question, whether to have the checkpoint be kernel-guided, or userspace
guided, is one we really need to talk about.

> I agree that we should not export useless interface to user but even

If we use it to guide checkpointing from the kernel, then none of it is
useless  :)

> without exporting anything we need support from the kernel internals
> (sysvipc in that case) to allow checkpointing. like setting the id. 
> right ? 
> 
> so there might be some common ground with some new user space interface.
> That's what we are looking for.

Pierre, do you want to break out the internal support (either from your
patchset, or from openvz's) and post that separately?  Then the small
patch on top of that to either present the set_id functionality to
userspace or to use it in a kernel-guided restore should be trivial.

thanks,
-serge

> > So until there is some user-space usage scenario of the patch I missed -
> > i wouldn't commit it.
> 
> Pierre has a user space tool to use it. quite simple. 
> 
> C.
> _______________________________________________
> Containers mailing list
> Containers@lists.linux-foundation.org
> https://lists.linux-foundation.org/mailman/listinfo/containers
_______________________________________________
Containers mailing list
Containers@lists.linux-foundation.org
https://lists.linux-foundation.org/mailman/listinfo/containers