Re: [PATCH] Reinstate "resource: avoid unnecessary lookups in find_next_iomem_res()"

[David Hildenbrand (Red Hat)]

On 11/24/25 17:53, Ilias Stamatis wrote:
> Commit 97523a4edb7b ("kernel/resource: remove first_lvl / siblings_only
> logic") removed an optimization introduced by commit 756398750e11
> ("resource: avoid unnecessary lookups in find_next_iomem_res()"). That
> was not called out in the message of the first commit explicitly so it's
> not entirely clear whether removing the optimization happened
> inadvertently or not.

Remembering the history, we have some things where the top might not
fully describe what the lower levels do.

An example is for example found here:

Author: Dan Williams <dan.j.williams@xxxxxxxxx>
Date:   Thu Feb 16 00:36:02 2023 -0800

    dax/kmem: Fix leak of memory-hotplug resources
    
    While experimenting with CXL region removal the following corruption of
    /proc/iomem appeared.
    
    Before:
    f010000000-f04fffffff : CXL Window 0
      f010000000-f02fffffff : region4
        f010000000-f02fffffff : dax4.0
          f010000000-f02fffffff : System RAM (kmem)

The CXL Windows will certainly not match System RAM, as one example.

How would your change affect such cases?


--
Cheers

David