Re: [PATCH V2] highmem: Fix kmap_to_page() for kmap_local_page() addresses

From: Andrew Morton
Date: Thu Oct 06 2022 - 16:33:50 EST

On Wed, 5 Oct 2022 21:05:55 -0700 ira.weiny@xxxxxxxxx wrote:

> kmap_to_page() is used to get the page for a virtual address which may
> be kmap'ed. Unfortunately, kmap_local_page() stores mappings in a
> thread local array separate from kmap(). These mappings were not
> checked by the call.
> Check the kmap_local_page() mappings and return the page if found.
> Because it is intended to remove kmap_to_page() add a warn on once to
> the kmap checks to flag potential issues early.

What were the user-visible runtime effects of this?

Are we able to identify a Fixes:?