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

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Message-Id: <20111006161056.e1cf56ec.akpm@linux-foundation.org>
Date:	Thu, 6 Oct 2011 16:10:56 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Nicolas Pitre <nicolas.pitre@...aro.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 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?

> 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?

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

Yes, the naming scheme in there is gruseome.
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