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From: Kirill Korotaev <dev@sw.ru>
To: Pierre Peiffer <pierre.peiffer@bull.net>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
	containers@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2.6.24-rc8-mm1 09/15] (RFC) IPC: new kernel API to change an ID
Date: Thu, 31 Jan 2008 12:54:10 +0300	[thread overview]
Message-ID: <47A19AC2.7040709@sw.ru> (raw)
In-Reply-To: <47A18E47.5050206@bull.net>

Why user space can need this API? for checkpointing only?
Then I would not consider it for inclusion until it is clear how to implement checkpointing.

As for me personally - I'm against exporting such APIs, since they are not needed in real-life user space applications and maintaining it forever for compatibility doesn't worth it.
Also such APIs allow creation of non-GPL checkpointing in user-space, which can be of concern as well.

Kirill


Pierre Peiffer wrote:
> Hi again,
> 
> 	Thinking more about this, I think I must clarify why I choose this way.
> In fact, the idea of these patches is to provide the missing user APIs (or
> extend the existing ones) that allow to set or update _all_ properties of all
> IPCs, as needed in the case of the checkpoint/restart of an application (the
> current user API does not allow to specify an ID for a created IPC, for
> example). And this, without changing the existing API of course.
> 
> 	And msgget(), semget() and shmget() does not have any parameter we can use to
> specify an ID.
> 	That's why I've decided to not change these routines and add a new control
> command, IP_SETID, with which we can can change the ID of an IPC. (that looks to
> me more straightforward and logical)
> 
> 	Now, this patch is, in fact, only a preparation for the patch 10/15 which
> really complete the user API by adding this IPC_SETID command.
> 
> (... continuing below ...)
> 
> Alexey Dobriyan wrote:
>> On Tue, Jan 29, 2008 at 05:02:38PM +0100, pierre.peiffer@bull.net wrote:
>>> This patch provides three new API to change the ID of an existing
>>> System V IPCs.
>>>
>>> These APIs are:
>>> 	long msg_chid(struct ipc_namespace *ns, int id, int newid);
>>> 	long sem_chid(struct ipc_namespace *ns, int id, int newid);
>>> 	long shm_chid(struct ipc_namespace *ns, int id, int newid);
>>>
>>> They return 0 or an error code in case of failure.
>>>
>>> They may be useful for setting a specific ID for an IPC when preparing
>>> a restart operation.
>>>
>>> To be successful, the following rules must be respected:
>>> - the IPC exists (of course...)
>>> - the new ID must satisfy the ID computation rule.
>>> - the entry in the idr corresponding to the new ID must be free.
>>>  ipc/util.c          |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>  ipc/util.h          |    1 +
>>>  8 files changed, 197 insertions(+)
>> For the record, OpenVZ uses "create with predefined ID" method which
>> leads to less code. For example, change at the end is all we want from
>> ipc/util.c .
> 
> And in fact, you do that from kernel space, you don't have the constraint to fit
> the existing user API.
> Again, this patch, even if it presents a new kernel API, is in fact a
> preparation for the next patch which introduces a new user API.
> 
> Do you think that this could fit your need ?
> 

  reply	other threads:[~2008-01-31  9:55 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-29 16:02 [PATCH 2.6.24-rc8-mm1 00/15] IPC: code rewrite + new functionalities pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 01/15] IPC/semaphores: code factorisation pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 02/15] IPC/shared memory: introduce shmctl_down pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 03/15] IPC/message queues: introduce msgctl_down pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 04/15] IPC/semaphores: move the rwmutex handling inside semctl_down pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 05/15] IPC/semaphores: remove one unused parameter from semctl_down() pierre.peiffer
2008-01-31  8:32   ` Nadia Derbey
2008-01-31 10:18     ` Pierre Peiffer
2008-01-31 11:30       ` Nadia Derbey
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 06/15] IPC: get rid of the use *_setbuf structure pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 07/15] IPC: introduce ipc_update_perm() pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 08/15] IPC: consolidate all xxxctl_down() functions pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 09/15] (RFC) IPC: new kernel API to change an ID pierre.peiffer
2008-01-29 21:06   ` Alexey Dobriyan
2008-01-30  9:52     ` Pierre Peiffer
2008-01-31  9:00     ` Pierre Peiffer
2008-01-31  9:54       ` Kirill Korotaev [this message]
2008-01-31 11:57         ` Pierre Peiffer
2008-01-31 13:11           ` Kirill Korotaev
2008-01-31 16:10             ` Cedric Le Goater
2008-02-04 13:41               ` Kirill Korotaev
2008-02-04 14:06                 ` [Devel] " Pavel Emelyanov
2008-02-04 15:00                   ` Daniel Lezcano
2008-02-04 15:16                     ` Pavel Emelyanov
2008-02-05  9:51           ` Oren Laadan
2008-02-05 18:00             ` Dave Hansen
2008-02-05 18:42             ` Serge E. Hallyn
2008-02-06  2:07               ` Oren Laadan
2008-02-06  5:00                 ` Serge E. Hallyn
2008-02-08 10:12               ` Pierre Peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 10/15] (RFC) IPC: new IPC_SETID command to modify " pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 11/15] (RFC) IPC: new IPC_SETALL command to modify all settings pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 12/15] (RFC) IPC/semaphores: make use of RCU to free the sem_undo_list pierre.peiffer
2008-01-30 21:26   ` Serge E. Hallyn
2008-01-31  9:52     ` Pierre Peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 13/15] (RFC) IPC/semaphores: per <pid> semundo file in procfs pierre.peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 14/15] (RFC) IPC/semaphores: prepare semundo code to work on another task than current pierre.peiffer
2008-01-30 21:44   ` Serge E. Hallyn
2008-01-31  9:48     ` Pierre Peiffer
2008-01-31 18:01       ` Serge E. Hallyn
2008-02-01 12:09         ` Pierre Peiffer
2008-01-29 16:02 ` [PATCH 2.6.24-rc8-mm1 15/15] (RFC) IPC/semaphores: add write() operation to semundo file in procfs pierre.peiffer
2008-02-02 18:23 ` [PATCH 2.6.24-rc8-mm1 00/15] IPC: code rewrite + new functionalities Pavel Machek
2008-02-04 13:52   ` Pierre Peiffer
2008-02-04 15:44   ` Benjamin Thery
2008-02-04 19:51     ` Pavel Machek

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