From mboxrd@z Thu Jan  1 00:00:00 1970
From: Changli Gao <xiaosuo@gmail.com>
Subject: Re: [PATCH] fs: use kmalloc() to allocate fdmem if possible
Date: Tue, 4 May 2010 12:20:43 +0800
Message-ID: <h2n412e6f7f1005032120t546ecd99w4e56146c54e5b6ad@mail.gmail.com>
References: <viro@zeniv.linux.org.uk> <1272818776-7729-1-git-send-email-xiaosuo@gmail.com>
	<4BDDB6E9.4060703@redhat.com> <201005030915.FCD09385.FFHVOMJtSLOFQO@I-love.SAKURA.ne.jp>
	<4BDE67DA.4080004@redhat.com> <y2z412e6f7f1005030005vc3be4977z3add08bfc72d1c44@mail.gmail.com>
	<4BDE7E66.8030509@redhat.com> <m2l412e6f7f1005030052ka39a33ceke8c6b61553ba007f@mail.gmail.com>
	<4BDE8E24.5050200@redhat.com> <1272878032.2226.27.camel@edumazet-laptop>
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Cc: Avi Kivity <avi@redhat.com>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	jslaby@suse.cz, akpm@linux-foundation.org,
	paulmck@linux.vnet.ibm.com, adobriyan@gmail.com, mingo@elte.hu,
	peterz@infradead.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
To: Eric Dumazet <eric.dumazet@gmail.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <1272878032.2226.27.camel@edumazet-laptop>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

On Mon, May 3, 2010 at 5:13 PM, Eric Dumazet <eric.dumazet@gmail.com> w=
rote:
>
> /*
> =A0* Warning: if size is not a power of two, kmalloc() might
> =A0* waste memory because of its requirements.
> =A0*/
> void *kvmalloc(size_t size)
> {
> =A0 =A0 =A0 =A0void *ptr =3D kmalloc(size, GFP_KERNEL | __GFP_NOWARN)=
;
>
> =A0 =A0 =A0 =A0if (ptr)
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0return ptr;
> =A0 =A0 =A0 =A0return vmalloc(size);
> }

we can use alloc_pages_exact()/free_pages_exact() when size is larger
than PAGE_SIZE, then size isn't needed to be a power of two.

void *kvmalloc(size_t size)
{
      void *ptr;

      if (size < PAGE_SIZE)
          return kmalloc(size, GFP_KERNEL);
      ptr =3D alloc_pages_exact(size, GFP_KERNEL | __GFP_NOWARN);
      if (ptr)
          return ptr;
      return vmalloc(size);
}

void *kvfree(void *ptr, size_t size)
{
       BUG_ON(in_interrupt());
       if (size < PAGE_SIZE)
            kfree(ptr);
       else if (is_vmalloc_addr(ptr))
            vfree(ptr);
       else
            free_pages_exact(ptr, size);
}

>
> void kvfree(void *ptr)
> {
> =A0 =A0 =A0 =A0BUG_ON(in_interrupt());
> =A0 =A0 =A0 =A0if (is_vmalloc_addr(ptr))
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0vfree(ptr);
> =A0 =A0 =A0 =A0else
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0kfree(ptr);
> }
>