Re: [PATCH v8 2/5] ipc: add sysctl to specify desired next objectid

[Stanislav Kinsbursky]

25.10.2012 01:41, Andrew Morton ÐÐÑÐÑ:
> On Wed, 24 Oct 2012 19:35:09 +0400
> Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx> wrote:
>
> > This patch adds 3 new variables and sysctls to tune them (by one "next_id"
> > variable for messages, semaphores and shared memory respectively).
> > This variable can be used to set desired id for next allocated IPC object.
> > By default it's equal to -1 and old behaviour is preserved.
> > If this variable is non-negative, then desired idr will be extracted from it
> > and used as a start value to search for free IDR slot.
> >
> > Notes:
> > 1) this patch doesn't garantee, that new object will have desired id. So it's
> > up to user space how to handle new object with wrong id.
> > 2) After sucessfull id allocation attempt, "next_id" will be set back to -1
> > (if it was non-negative).
> >
> > --- a/ipc/ipc_sysctl.c
> > +++ b/ipc/ipc_sysctl.c
> > @@ -158,6 +158,7 @@ static int proc_ipcauto_dointvec_minmax(ctl_table *table, int write,
> >
> >   static int zero;
> >   static int one = 1;
> > +static int int_max = INT_MAX;
> >
> >   static struct ctl_table ipc_kern_table[] = {
> >   	{
> > @@ -227,6 +228,33 @@ static struct ctl_table ipc_kern_table[] = {
> >   		.extra1		= &zero,
> >   		.extra2		= &one,
> >   	},
> > +	{
> > +		.procname	= "sem_next_id",
> > +		.data		= &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
> > +		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
> > +		.mode		= 0644,
> > +		.proc_handler	= proc_ipc_dointvec_minmax,
> > +		.extra1		= &zero,
> > +		.extra2		= &int_max,
> > +	},
> > +	{
> > +		.procname	= "msg_next_id",
> > +		.data		= &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
> > +		.maxlen		= sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
> > +		.mode		= 0644,
> > +		.proc_handler	= proc_ipc_dointvec_minmax,
> > +		.extra1		= &zero,
> > +		.extra2		= &int_max,
> > +	},
> > +	{
> > +		.procname	= "shm_next_id",
> > +		.data		= &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
> > +		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
> > +		.mode		= 0644,
> > +		.proc_handler	= proc_ipc_dointvec_minmax,
> > +		.extra1		= &zero,
> > +		.extra2		= &int_max,
> > +	},
> >   	{}
> >   };
>
> ipc_kern_table[] is (badly) documented in
> Documentation/sysctl/kernel.txt.  Can we at least mention these
> controls in there?  Better, create a new way of properly documenting
> each control and document these three in that manner?  Better still,
> document all the other ones as well ;)

Yes, sure. I'll do my best.

> The patch adds these controls to CONFIG_CHECKPOINT_RESTORE=n kernels.
> Why is this?

I'll fix this.

--
Best regards,
Stanislav Kinsbursky
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