Re: How to get the address of the page structure from the given virtual address?

[Jonathan Corbet <corbet@lwn.net>]

On Tue, 11 Aug 2009 20:01:41 +0530
"B.Vinai Kumar" <vinaibangala2001@gmail.com> wrote:

> 1) I allocated 8 pages using alloc_pages(GFP_KERNEL, 3). This function
> returns the pointer to the first page's page structure.
> How can I get the page structure address of the remaining 7 pages?

They will be immediately following the first page structure in the
system memory map - they are contiguous pages, after all.  So just use
pointer arithmetic to find them.  

Inquiring minds are indeed curious as to why you need them, though :)
> 
> 2) There is a function page_address() which takes the page structure
> as an argument and returns the virtual address of the page
>  that is pointed by that page structure. 

Note that page_address() may not give you a valid address if it's a
high-memory page which is not currently mapped.

> Is there any method which
> retrives the address of the page structure?

Use virt_to_page() for normal kernel virtual addresses,
vmalloc_to_page() for memory in the vmalloc range.

jon