Re: [RFC PATCH 00/11] mm/mempolicy: Make task->mempolicy externally modifiable via syscall and procfs

[Gregory Price <gregory.price@memverge.com>]

On Tue, Nov 28, 2023 at 10:45:02AM +0100, Michal Hocko wrote:
> > 2) Should we combine all the existing operations into set_mempolicy2 and
> >    add an operation arg.
> > 
> >    set_mempolicy2(pidfd, arg_struct, len)
> > 
> >    struct {
> >      int pidfd; /* optional */
> >      int operation; /* describe which op_args to use */
> >      union {
> >        struct {
> >        } set_mempolicy;
> >        struct {
> >        } set_vma_home_node;
> >        struct {
> >        } mbind;
> >        ...
> >      } op_args;
> >    } args;
> > 
> >    capturing:
> >      sys_set_mempolicy
> >      sys_set_mempolicy_home_node
> >      sys_mbind
> > 
> >    or should we just make a separate interface for mbind/home_node to
> >    limit complexity of the single syscall?
> 
> My preference would be to go with specific syscalls. Multiplexing
> syscalls have turned much more complex and less flexible over time.
> Just have a look at futex.

got it, that simplifies things a bit.  I can pull my set/get mempolicy2
work forward and just keep the interfaces pretty much the same. Only
difference being an argument structure that is extensible and possibly
some additional refactoring in do_get_mempolicy to make things a bit
cleaner.

~Gregory