linux-kernel - Re: [PATCH/RFC] mm: add vm_area_add

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Message-ID: <alpine.LFD.2.02.1110062012250.9106@xanadu.home>
Date:	Thu, 6 Oct 2011 20:17:03 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH/RFC] mm: add vm_area_add_early()

On Thu, 6 Oct 2011, Andrew Morton wrote:

> On Wed, 14 Sep 2011 14:35:21 -0400 (EDT)
> Nicolas Pitre <nicolas.pitre@...aro.org> wrote:
> 
> > 
> > The existing vm_area_register_early() allows for early vmalloc space
> > allocation.  However upcoming cleanups in the ARM architecture require
> > that some fixed locations in the vmalloc area be reserved also very early.
> > 
> > The name "vm_area_register_early" would have been a good name for the
> > reservation part without the allocation.  Since it is already in use with
> > different semantics, let's create vm_area_add_early() instead.
> > 
> > Both vm_area_register_early() and vm_area_add_early() can be used together
> > meaning that the former is now implemented using the later where it is
> > ensured that no conflicting areas are added, but no attempt is made to
> > make the allocation scheme in vm_area_register_early() more sophisticated.
> > After all, you must know what you're doing when using those functions.
> > 
> > Signed-off-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> > ---
> > 
> > Comments / ACKs appreciated.
> 
> Deafening silence?

I interpreted it as "no objections".

> > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
> > index 9332e52ea8..e7d2cba995 100644
> > --- a/include/linux/vmalloc.h
> > +++ b/include/linux/vmalloc.h
> > @@ -130,6 +130,7 @@ extern long vwrite(char *buf, char *addr, unsigned long count);
> >   */
> >  extern rwlock_t vmlist_lock;
> >  extern struct vm_struct *vmlist;
> > +extern __init void vm_area_add_early(struct vm_struct *vm);
> >  extern __init void vm_area_register_early(struct vm_struct *vm, size_t align);
> >  
> >  #ifdef CONFIG_SMP
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index 7ef0903058..bf20a0ff95 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -1118,6 +1118,31 @@ void *vm_map_ram(struct page **pages, unsigned int count, int node, pgprot_t pro
> >  EXPORT_SYMBOL(vm_map_ram);
> >  
> >  /**
> > + * vm_area_add_early - add vmap area early during boot
> > + * @vm: vm_struct to add
> > + *
> > + * This function is used to add fixed kernel vm area to vmlist before
> > + * vmalloc_init() is called.  @vm->addr, @vm->size, and @vm->flags
> > + * should contain proper values and the other fields should be zero.
> > + *
> > + * DO NOT USE THIS FUNCTION UNLESS YOU KNOW WHAT YOU'RE DOING.
> > + */
> > +void __init vm_area_add_early(struct vm_struct *vm)
> > +{
> > +	struct vm_struct *tmp, **p;
> > +
> > +	for (p = &vmlist; (tmp = *p) != NULL; p = &tmp->next) {
> > +		if (tmp->addr >= vm->addr) {
> > +			BUG_ON(tmp->addr < vm->addr + vm->size);
> > +			break;
> > +		} else
> > +			BUG_ON(tmp->addr + tmp->size > vm->addr);
> > +	}
> > +	vm->next = *p;
> > +	*p = vm;
> > +}
> > +
> > +/**
> >   * vm_area_register_early - register vmap area early during boot
> >   * @vm: vm_struct to register
> >   * @align: requested alignment
> > @@ -1139,8 +1164,7 @@ void __init vm_area_register_early(struct vm_struct *vm, size_t align)
> >  
> >  	vm->addr = (void *)addr;
> >  
> > -	vm->next = vmlist;
> > -	vmlist = vm;
> > +	vm_area_add_early(vm);
> >  }
> >  
> >  void __init vmalloc_init(void)
> 
> I tossed this into my tree for a bit of testing, assuming it's
> up-to-date and still desired?

Yes it is, on both counts.

> Feel free to add it to some ARM tree.  I'll drop my copy when that
> turns up in linux-next.

So I did, however I'm postponing the whole series that depend on this to 
the next cycle because of other prerequisite cleanups that are going in 
this cycle from different paths.

> Yes, the naming scheme in there is gruseome.

I didn't want to go as far as renaming it across the tree, in case other 
people are relying on the current name in their own tree.


Nicolas
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