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

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
[email protected]

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
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