Re: [PATCH] x86: introduce bootmem_state -v2

[Jeremy Fitzhardinge]

Ingo Molnar wrote:
> * Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>   
> > On Fri, 6 Mar 2009 20:12:49 +0100
> > Ingo Molnar <mingo@xxxxxxx> wrote:
> >
> >     
> > > * Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> > >
> > >       
> > > > Impact: cleanup
> > > >
> > > > extend after_bootmem and after_init_bootmem to bootmem_state
> > > > and will have BEFORE_BOOTMEM, DURING_BOOTMEM, AFTER_BOOTMEM
> > > >
> > > > v2: style changes according to ingo
> > > >
> > > > Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> > > >
> > > > ---
> > > >  arch/x86/kernel/setup.c |    1 +
> > > >  arch/x86/mm/init.c      |   13 +++++++------
> > > >  arch/x86/mm/init_32.c   |   28 ++++++++++++++++++++--------
> > > >  arch/x86/mm/init_64.c   |   33 +++++++++++++++++++--------------
> > > >  include/linux/mm.h      |    9 +++++++++
> > > >  5 files changed, 56 insertions(+), 28 deletions(-)
> > > >         
> > > > Index: linux-2.6/include/linux/mm.h
> > > > ===================================================================
> > > > --- linux-2.6.orig/include/linux/mm.h
> > > > +++ linux-2.6/include/linux/mm.h
> > > > @@ -1067,6 +1067,15 @@ extern void __init mmap_init(void);
> > > >  extern void show_mem(void);
> > > >  extern void si_meminfo(struct sysinfo * val);
> > > >  extern void si_meminfo_node(struct sysinfo *val, int nid);
> > > > +
> > > > +enum bootmem_state {
> > > > +	BEFORE_BOOTMEM,
> > > > +	DURING_BOOTMEM,
> > > > +	AFTER_BOOTMEM
> > > > +};
> > > > +
> > > > +extern enum bootmem_state bootmem_state;
> > > > +
> > > >  extern int after_bootmem;
> > > >         
> > > Btw., the after_bootmem variable itself should either move to 
> > > x86 (and arch/sh), or should be defined in mm/bootmem.c.
> > >
> > > Right now we have this weird mm.h construct that is not actually 
> > > useful to generic code.
> > >
> > > Andrew, what would be your preference?
> > >
> > >       
> > If two architectures are using it then it should be provided 
> > by core kernel?
> >
> > This is obvious if the state transitions are occurring in 
> > core-kernel code, but if the transitions are happening in arch 
> > code then making it a core concept assumes consistency between 
> > different architectures which might not exist.
> >
> > IOW: dunno.
> >     
>
> Core kernel could provide a wrapper allocator which calls the 
> right method depending on which state we are in. It will call 
> bootmem_alloc() if called early, and kmalloc() if called later. 
> Or something like that. Would there be any utility in that?
>   

Yes, so long as you're never intending to free the memory (since you 
won't know which free function to use for a given pointer - assuming one 
even exists).  And code which does:

   p = use_anytime_alloctor();

...
   kfree(p);        /* I know it was really allocated by kmalloc */


should be shot.

   J
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