[openib-general] Re: [PATCH][RFC][0/4] InfiniBand userspace verbs implementation

[Timur Tabi]

Andrew Morton wrote:

> This is because there is no file descriptor or anything else associated
> with the pages which permits the kernel to clean stuff up on unclean
> application exit.  Also there are the obvious issues with permitting
> pinning of unbounded amounts of memory.

Then that might explain the "bug" that we're seeing with get_user_pages().  We've been 
assuming that get_user_pages() mappings are permanent.

Well, I was just about to re-implement get_user_pages() support in our driver to 
demonstrate the bug.  I guess I'll hold off on that.

If you look at the Infiniband code that was recently submitted, I think you'll see it does 
exactly that: after calling mlock(), the driver calls get_user_pages(), and it stores the 
page mappings for future use.

-- 
Timur Tabi
Staff Software Engineer
timur.tabi at ammasso.com

One thing a Southern boy will never say is,
"I don't think duct tape will fix it."
      -- Ed Smylie, NASA engineer for Apollo 13