On Fri, 21 Oct 2005, KAMEZAWA Hiroyuki wrote:
>
> Christoph Lameter wrote:
> > + /* Is the user allowed to access the target nodes? */
> > + if (!nodes_subset(new, cpuset_mems_allowed(task)))
> > + return -EPERM;
> > +
> How about this ?
> +cpuset_update_task_mems_allowed(task, new); (this isn't implemented now)
>
> > + err = do_migrate_pages(mm, &old, &new, MPOL_MF_MOVE);
> > +
>
> or it's user's responsibility to updates his mempolicy before
> calling sys_migrage_pages() ?
>
The user cannot always add a memory node to a cpuset, for example if this
cpuset is inside another cpuset that is owned by another user. (i.e the
case where the administrator wants to dedicate a part of the machine to a
user).
The kernel checks for these permission issues, conflicts with other
mem_exclusive cpusets, etc... when you write in the 'mems' file.
Automatically updating the ->mems_allowed field as you suggest would
require that the kernel do the same checks in sys_migrage_pages(). Sounds
not as a very good idea to me.
Simon.
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