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Message-ID: <84144f020811172257k2c749bc3g98c3596ebb603cd2@mail.gmail.com>
Date: Tue, 18 Nov 2008 08:57:07 +0200
From: "Pekka Enberg" <penberg@cs.helsinki.fi>
To: "Lai Jiangshan" <laijs@cn.fujitsu.com>
Subject: Re: [PATCH V2 1/1] mm: introduce kvmalloc()/kvfree()
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
       "David Miller" <davem@davemloft.net>, "Dave Airlie" <airlied@gmail.com>,
       "Paul Menage" <menage@google.com>, kamezawa.hiroyu@jp.fujitsu.com,
       "Balbir Singh" <balbir@linux.vnet.ibm.com>,
       "Arjan van de Ven" <arjan@infradead.org>, "Jan Kara" <jack@suse.cz>,
       "Jes Sorensen" <jes@sgi.com>,
       "KOSAKI Motohiro" <kosaki.motohiro@jp.fujitsu.com>, dada1@cosmosbay.com,
       "Alexey Dobriyan" <adobriyan@gmail.com>,
       "Jens Axboe" <jens.axboe@oracle.com>,
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On Mon, Nov 17, 2008 at 2:26 PM, Lai Jiangshan <laijs@cn.fujitsu.com> wrote:
> @@ -163,6 +165,38 @@ char *strndup_user(const char __user *s, long n)
>  }
>  EXPORT_SYMBOL(strndup_user);
>
> +/**
> + * kvmalloc - allocate memory by kmalloc() or vmalloc()
> + *
> + * if @size <= PAGE_SIZE, memory is allocated by kmalloc(),
> + * otherwise by vmalloc().
> + *
> + * NOTICE: Generally, you should use kmalloc() or vmalloc() directly.
> + * kvmalloc() is provided for some special condition.

You might as well explicitly state what those special conditions are here.

> + */
> +void *kvmalloc(unsigned long size, gfp_t flags)
> +{
> +       if (size <= PAGE_SIZE)
> +               return kmalloc(size, flags & ~__GFP_HIGH);
> +       else
> +               return __vmalloc(size, flags | __GFP_HIGHMEM, PAGE_KERNEL);
> +}
> +EXPORT_SYMBOL(kvmalloc);
> +
> +/**
> + * kvfree - free the memory by kfree(), or vfree() if it is vmalloc addr
> + */
> +void kvfree(void *ptr)
> +{
> +       BUG_ON(in_interrupt());

I wonder if this should be a WARN_ON() to let the machine limp along
for a while if it can. At least in the kfree() case people can catch
the oops trace more easily that way.

> +
> +       if (is_vmalloc_addr(ptr))
> +               vfree(ptr);
> +       else
> +               kfree(ptr);
> +}
> +EXPORT_SYMBOL(kvfree);
> +
>  #ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
>  void arch_pick_mmap_layout(struct mm_struct *mm)
>  {
>
>
> --
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