Re: [PATCH V5 0/9] Fixes for vhost metadata acceleration

[Jason Wang]

On 2019/8/14 äå12:41, Christoph Hellwig wrote:
> On Tue, Aug 13, 2019 at 08:57:07AM -0300, Jason Gunthorpe wrote:
> > On Tue, Aug 13, 2019 at 04:31:07PM +0800, Jason Wang wrote:
> >
> > > What kind of issues do you see? Spinlock is to synchronize GUP with MMU
> > > notifier in this series.
> > A GUP that can't sleep can't pagefault which makes it a really weird
> > pattern
> get_user_pages/get_user_pages_fast must not be called under a spinlock.
> We have the somewhat misnamed __get_user_page_fast that just does a
> lookup for existing pages and never faults for a few places that need
> to do that lookup from contexts where we can't sleep.


Yes, I do use __get_user_pages_fast() in the code.

Thanks