[CRIU] [PATCH v3 3/4] ipc/sysctl: c/r kernel.{msg_next_id, sem_next_id, shm_next_id}

[Pavel Emelyanov]

On 07/14/2016 05:20 PM, 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
> 
> v3: do one sysctl_op for all xxx_next_id(as sysctl_op is quiet slow)
> 
> Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
> ---
>  criu/ipc_ns.c        | 38 +++++++++++++++++++++++++++++++++++++-
>  images/ipc-var.proto |  3 +++
>  2 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/criu/ipc_ns.c b/criu/ipc_ns.c
> index 02fb9a0..d2eda22 100644
> --- a/criu/ipc_ns.c
> +++ b/criu/ipc_ns.c
> @@ -313,6 +313,15 @@ static int ipc_sysctl_req(IpcVarEntry *e, int op)
>  		{ "fs/mqueue/msgsize_default",	&e->mq_msgsize_default,	CTL_U32 },
>  	};
>  
> +	struct sysctl_req req_next_tmp[] = {
> +		{ "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 },
> +	};
> +
> +	struct sysctl_req req_next[3];
> +	int nr = 0;
> +
>  	int ret;
>  
>  	ret = sysctl_op(req, ARRAY_SIZE(req), op, CLONE_NEWIPC);
> @@ -324,8 +333,21 @@ 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);

First call to sysctl_op ...

> +	if (ret)
> +		return ret;
> +
> +	/* Skip xxx_next_id which were -1 or haven't existed on dump */
> +	if (e->has_msg_next_id)
> +		req_next[nr++] = req_next_tmp[0];
> +	if (e->has_sem_next_id)
> +		req_next[nr++] = req_next_tmp[1];
> +	if (e->has_shm_next_id)
> +		req_next[nr++] = req_next_tmp[2];
> +	if (nr)
> +		return sysctl_op(req_next, nr, op, CLONE_NEWIPC);


... 2nd call to sysctl_op. Please, leave only one, we do tricks
on size calculations anyway.

> +	return 0;
>  }
>  
>  /*
> @@ -421,6 +443,9 @@ 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 +453,17 @@ 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;
>  }
>