Re: [PATCH v1] mm/gup: remove (VM_)BUG_ONs

[David Hildenbrand <david@redhat.com>]

On 04.06.25 16:05, David Hildenbrand wrote:
> Especially once we hit one of the assertions in
> sanity_check_pinned_pages(), observing follow-up assertions failing
> in other code can give good clues about what went wrong, so use
> VM_WARN_ON_ONCE instead.
> 
> While at it, let's just convert all VM_BUG_ON to VM_WARN_ON_ONCE as
> well. Add one comment for the pfn_valid() check.
> 
> We have to introduce VM_WARN_ON_ONCE_VMA() to make that fly.
> 
> Drop the BUG_ON after mmap_read_lock_killable(), if that ever returns
> something > 0 we're in bigger trouble. Convert the other BUG_ON's into
> VM_WARN_ON_ONCE as well, they are in a similar domain "should never
> happen", but more reasonable to check for during early testing.
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: "Liam R. Howlett" <Liam.Howlett@oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Mike Rapoport <rppt@kernel.org>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Cc: Peter Xu <peterx@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> 
> Wanted to do this for a long time, but my todo list keeps growing ...
> 
> Based on mm/mm-unstable

Thanks everybody for the review -- that must be one of my patches with
most RB's/ACK's/feedback :)

The following fixup on top to use the _FOLIO variant where possible
(thanks Lorenzo).

 From c3b2567f169f10f96b94d61369d8492e3095f187 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Fri, 6 Jun 2025 10:08:20 +0200
Subject: [PATCH] fixup

Signed-off-by: David Hildenbrand <david@redhat.com>
---
  mm/gup.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/gup.c b/mm/gup.c
index 3c3931fcdd820..25fd0d895e453 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -64,7 +64,7 @@ static inline void sanity_check_pinned_pages(struct page **pages,
  		    !folio_test_anon(folio))
  			continue;
  		if (!folio_test_large(folio) || folio_test_hugetlb(folio))
-			VM_WARN_ON_ONCE_PAGE(!PageAnonExclusive(&folio->page), page);
+			VM_WARN_ON_ONCE_FOLIO(!PageAnonExclusive(&folio->page), folio);
  		else
  			/* Either a PTE-mapped or a PMD-mapped THP. */
  			VM_WARN_ON_ONCE_PAGE(!PageAnonExclusive(&folio->page) &&
-- 
2.49.0


-- 
Cheers,

David / dhildenb