[CRIU] [PATCH 3/4] ipc/sysctl: c/r kernel.{msg_next_id, sem_next_id, shm_next_id}

[Pavel Emelyanov]

On 07/13/2016 04:06 PM, Pavel Tikhomirov wrote:
> 
> 
> On 07/13/2016 03:53 PM, Pavel Emelyanov wrote:
>> On 07/04/2016 10:47 AM, Pavel Tikhomirov wrote:
>>> These are only three left in ipc_kern_table which we haven't
>>> checkpointed yet, I'm not sure if somebody really uses them
>>> except criu, but to be consistent, beter not to change them
>>> while c/r.
>>>
>>> *We have these sysctls writable in VZ7 CT.
>>> https://jira.sw.ru/browse/PSBM-48397
>>>
>>> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
>>> ---
>>>  criu/ipc_ns.c        | 33 ++++++++++++++++++++++++++++++++-
>>>  images/ipc-var.proto |  3 +++
>>>  2 files changed, 35 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/criu/ipc_ns.c b/criu/ipc_ns.c
>>> index 02fb9a0..c75cfb5 100644
>>> --- a/criu/ipc_ns.c
>>> +++ b/criu/ipc_ns.c
>>> @@ -313,6 +313,12 @@ static int ipc_sysctl_req(IpcVarEntry *e, int op)
>>>  		{ "fs/mqueue/msgsize_default",	&e->mq_msgsize_default,	CTL_U32 },
>>>  	};
>>>
>>> +	struct sysctl_req req_next[] = {
>>> +		{ "kernel/msg_next_id", &e->msg_next_id, CTL_U32 },
>>> +		{ "kernel/sem_next_id", &e->sem_next_id, CTL_U32 },
>>> +		{ "kernel/shm_next_id", &e->shm_next_id, CTL_U32 },
>>> +	};
>>> +
>>>  	int ret;
>>>
>>>  	ret = sysctl_op(req, ARRAY_SIZE(req), op, CLONE_NEWIPC);
>>> @@ -324,8 +330,19 @@ static int ipc_sysctl_req(IpcVarEntry *e, int op)
>>>  		return 0;
>>>  	}
>>>
>>> -	return sysctl_op(req_mq, ARRAY_SIZE(req_mq) - (e->has_mq_msg_default ? 0 : 2),
>>> +	ret = sysctl_op(req_mq, ARRAY_SIZE(req_mq) - (e->has_mq_msg_default ? 0 : 2),
>>>  	                 op, CLONE_NEWIPC);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	/* Skip xxx_next_id which were -1 or haven't existed on dump */
>>> +	if (e->has_msg_next_id && (ret = sysctl_op(&req_next[0], 1, op, CLONE_NEWIPC)))
>>> +		return ret;
>>> +	if (e->has_sem_next_id && (ret = sysctl_op(&req_next[1], 1, op, CLONE_NEWIPC)))
>>> +		return ret;
>>> +	if (e->has_shm_next_id && (ret = sysctl_op(&req_next[2], 1, op, CLONE_NEWIPC)))
>>
>> Can we do it in one call to sysctl_op?
> 
> We will have to create proper req array for all possible combinations of 
> has_xxx_next_id, for (1,0,1) that don't look good from my POV.

Just declare the op-s array big enough and

if (e->has_foo_next)
	ops[i++] = { "kernel/foo_next", &e->foo_next, CTL_U32 };

or smth like this.

>>
>>> +		return ret;
>>> +	return 0;
>>>  }
>>>
>>>  /*
>>> @@ -421,6 +438,9 @@ static int dump_ipc_var(struct cr_img *img)
>>>  		goto err;
>>>  	var.has_mq_msg_default = true;
>>>  	var.has_mq_msgsize_default = true;
>>> +	var.has_msg_next_id = true;
>>> +	var.has_sem_next_id = true;
>>> +	var.has_shm_next_id = true;
>>>
>>>  	ret = ipc_sysctl_req(&var, CTL_READ);
>>>  	if (ret < 0) {
>>> @@ -428,6 +448,17 @@ static int dump_ipc_var(struct cr_img *img)
>>>  		goto err;
>>>  	}
>>>
>>> +	/*
>>> +	 * One can not write to msg_next_xxx sysctls -1,
>>> +	 * which is their initial value
>>> +	 */
>>> +	if (var.msg_next_id == -1)
>>> +		var.has_msg_next_id = false;
>>> +	if (var.sem_next_id == -1)
>>> +		var.has_sem_next_id = false;
>>> +	if (var.shm_next_id == -1)
>>> +		var.has_shm_next_id = false;
>>> +
>>>  	ret = pb_write_one(img, &var, PB_IPC_VAR);
>>>  	if (ret < 0) {
>>>  		pr_err("Failed to write IPC variables\n");
>>> diff --git a/images/ipc-var.proto b/images/ipc-var.proto
>>> index 153b167..4fd8362 100644
>>> --- a/images/ipc-var.proto
>>> +++ b/images/ipc-var.proto
>>> @@ -13,4 +13,7 @@ message ipc_var_entry {
>>>  	required uint32			mq_msgsize_max		= 12;
>>>  	optional uint32			mq_msg_default		= 13;
>>>  	optional uint32			mq_msgsize_default	= 14;
>>> +	optional uint32			msg_next_id		= 15;
>>> +	optional uint32			sem_next_id		= 16;
>>> +	optional uint32			shm_next_id		= 17;
>>>  }
>>>
>>
>