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

Jason Wang
2019-08-15T03:28:18Z

On 2019/8/14 上午12:41, 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