Re: [PATCH] __free_pages_ok oops

From: Benjamin LaHaise (bcrl@redhat.com)
Date: Thu Feb 07 2002 - 04:48:14 EST


On Wed, Feb 06, 2002 at 10:19:32PM -0800, Andrew Morton wrote:
> It's only a problem if this is the final put_page(). In the
> case of sendfile(), process-context code can be taught to take
> a temporary reference on the page, and only release it after the network
> stack is known to have finished with the page. sendfile is synchronous, yes?
>
> And in the case of all other skb frees, the underlying page
> won't be on the LRU. I hope.

sendfile isn't synchronous, nor is aio, which also relies on freeing pages
acquired from user mappings in irq/bh/whatever context. Restricting where
pages may be freed really ties our hands on what is possible for zero copy
io. (ie O_DIRECT, aio, sendfile, TUX all get hosed by this).

                -ben (who is really on vacation)

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