Re: [RFC] some page can't be migrated

From: Christoph Lameter
Date: Mon Jan 28 2008 - 14:09:28 EST


On Sat, 26 Jan 2008, Andrew Morton wrote:

> We call something(GFP_KERNEL) under rcu_read_lock()? I've lost track of
> the myriad flavours of rcu which we purport to support, but I don't think
> they'll all like us blocking under rcu_read_lock().
>
> We _won't_ block, because try_to_release_page() will see the NULL ->mapping
> and will call the non-blocking try_to_free_buffers(). But still, it looks
> bad, and will cause problems if someone decides to add a might_sleep_if()
> to try_to_release_page().
>
> So... I'd suggest that it would be better to add an apologetic comment and
> call direct into try_to_free_buffers().

Right. Looks good. PageWriteback cannot be set if we do not have a
mappig...

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