linux-kernel - RE: Could convert a buffer that allocated by vmalloc to pages?

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Message-ID: <Pine.LNX.4.64.0701231449110.16296@hermes-1.csi.cam.ac.uk>
Date:	Tue, 23 Jan 2007 14:50:19 +0000 (GMT)
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	Yu-Chen Wu <g944370@...nthu.edu.tw>
cc:	linux-kernel@...r.kernel.org
Subject: RE: Could convert a buffer that allocated by vmalloc to pages?

On Tue, 23 Jan 2007, Yu-Chen Wu wrote:
> I tried vmalloc_to_page() and I have some question.
> I print the "pages" in vm_struct structure of the buffer to compare the
> address get from vmalloc_to_page(), result as follows:

Both the code you are showing and your question do not make any sense 
to me...  You need to show all of the code not some random fragments...  
What the heck is L2vm for a start?

Best regards,

	Anton

> //===source code====
> L2cache=vmalloc(L2SIZE);// L2SIZE=40960
> printk(KERN_INFO "find_vm_struct OK:%x
> addr:%xnr_pages:%d\n",L2vm,L2vm->addr,L2vm->nr_pages);
> for(i=0;i<L2vm->nr_pages;i++)
>  {
>       if(L2vm->pages[i])
>          printk("page allocated:%x\n",page_address(L2vm->pages[i]));
>  }
> tpage=vmalloc_to_page(L2cache);
> printk(KERN_INFO "vmalloc_to_page tpage :%x\n",tpage);
> //===========info of dmesg==================
> [ 1561.768471] page allocated:73d65000
> [ 1561.768474] page allocated:781e9000
> [ 1561.768476] page allocated:6203f000
> [ 1561.768478] page allocated:57fdf000
> [ 1561.768481] page allocated:56ed4000
> [ 1561.768483] page allocated:56ed5000
> [ 1561.768485] page allocated:64ab6000
> [ 1561.768488] page allocated:7cc1e000
> [ 1561.768490] page allocated:60ea8000
> [ 1561.768492] page allocated:60ea9000
> [ 1561.768497] vmalloc_to_page tpage :7fcf7e18
> 
> Why the page address get from vmalloc_to_page is different with the first
> page address of the vm_struct (73d65000)?
> 
> THX
> -----Original Message-----
> From: linux-kernel-owner@...r.kernel.org
> [mailto:linux-kernel-owner@...r.kernel.org] On Behalf Of Anton Altaparmakov
> Sent: Tuesday, January 23, 2007 9:12 PM
> To: Yu-Chen Wu
> Cc: linux-kernel@...r.kernel.org
> Subject: Re: Could convert a buffer that allocated by vmalloc to pages?
> 
> On Tue, 2007-01-23 at 21:04 +0800, Yu-Chen Wu wrote:
> > Hi,
> > I write a driver have a big buffer (16MB,allocated by vmalloc).
> > I want to use the buffer to do DMA transmission so I need getting the
> pages
> > of the buffer.
> > Have any kernel API can do this?
> > My platform is x86_64 and 2GB RAM
> 
> vmalloc_to_page()...
> 
> See mm/memory.c for the function and how to use it.
> 
> Best regards,
> 
>         Anton
> 

-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/
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