Re: [PATCH v7 4/6] mm/memory-failure: short-circuit PG_reserved before get_hwpoison_page()

[Breno Leitao]

On Wed, May 13, 2026 at 09:49:28PM +0200, David Hildenbrand (Arm) wrote:
> On 5/13/26 17:39, Breno Leitao wrote:
> > The previous patch already classifies PG_reserved pages as
> > MF_MSG_KERNEL through the long path: get_hwpoison_page() calls
> > __get_hwpoison_page() which fails HWPoisonHandlable(), get_any_page()
> > exhausts its shake_page() retry budget, and the resulting
> > -ENOTRECOVERABLE is mapped to MF_MSG_KERNEL by the switch.  The
> > outcome is correct but the work in between is wasted: shake_page()
> > cannot turn a reserved page into a handlable one.
> 
> If really required, can we just move the check right there, into get_any_page() etc?

Sure, we might move it to get_any_page(). I took this current approach
based on the following facts:

1) Lance suggested it, and it sounded a good idea.
	https://lore.kernel.org/all/20260512124837.38883-1-lance.yang@xxxxxxxxx/

2) There is a _similar_ check close to this one in memory_failure(),
   just before this one:

  if (TestSetPageHWPoison(p)) {
  	....
	action_result()
	goto unlock_mutex;
  }

  and now

  if (PageReserved(p)) {
	...
  	action_result()
	goto unlock_mutes;
  }

3) I wanted to give get it as  real layering point, not handwaving.

That said, I will short-circuit reserved pages inside get_any_page(), in
an updated version.

Again, thanks for the review and direction!
--breno