Re: Questions about page IO of swapping

[Andrea Arcangeli <andrea@suse.de>]

On Mon, 22 May 2000, Ingo Oeser wrote:

>I thought encryption should be done before calling brw_page() in 
>mm/page_io.c:rw_swap_page_base()

only in the write case of course.

>and decryption in fs/buffer.c:after_unlock_page(), if the
>page->count is >0 after passing every other of the tests in this
>function.

If the page->count during swapping is zero then it's going to be a
bug. You shouldn't need to check the page count.

>So when is a page actually considered written to disk and when is
>it accessed first after this? 

Of course you have to encrypt on a kind of bounce page, not on the swap
cache. While decrypting you can decrypt in place instead.

>I have also problems tracking reads vs. writes, because this

I see. You can probably check if the page is uptodate or not to know if
it's a read or a write during disk completation.

Andrea

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux.eu.org/Linux-MM/