Commit 792b429d authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/gup: remove (VM_)BUG_ONs 

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.

[david@redhat.com: use the _FOLIO variant where possible, per Lorenzo]
  Link: https://lkml.kernel.org/r/844bd929-a551-48e3-a12e-285cd65ba580@redhat.com
Link: https://lkml.kernel.org/r/20250604140544.688711-1-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarSuren Baghdasaryan <surenb@google.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: default avatarSeongJae Park <sj@kernel.org>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7c33c6c4

include/linux/mmdebug.h

+12 −0
Original line number Diff line number Diff line
@@ -89,6 +89,17 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi); 
	}								\

	unlikely(__ret_warn_once);					\

})

#define VM_WARN_ON_ONCE_VMA(cond, vma)		({			\

	static bool __section(".data..once") __warned;			\

	int __ret_warn_once = !!(cond);					\

									\

	if (unlikely(__ret_warn_once && !__warned)) {			\

		dump_vma(vma);						\

		__warned = true;					\

		WARN_ON(1);						\

	}								\

	unlikely(__ret_warn_once);					\

})

#define VM_WARN_ON_VMG(cond, vmg)		({			\

	int __ret_warn = !!(cond);					\

									\
@@ -115,6 +126,7 @@ void vma_iter_dump_tree(const struct vma_iterator *vmi); 
#define VM_WARN_ON_FOLIO(cond, folio)  BUILD_BUG_ON_INVALID(cond)

#define VM_WARN_ON_ONCE_FOLIO(cond, folio)  BUILD_BUG_ON_INVALID(cond)

#define VM_WARN_ON_ONCE_MM(cond, mm)  BUILD_BUG_ON_INVALID(cond)

#define VM_WARN_ON_ONCE_VMA(cond, vma)  BUILD_BUG_ON_INVALID(cond)

#define VM_WARN_ON_VMG(cond, vmg)  BUILD_BUG_ON_INVALID(cond)

#define VM_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)

#define VM_WARN(cond, format...) BUILD_BUG_ON_INVALID(cond)

mm/gup.c

+19 −22
Original line number Diff line number Diff line
@@ -64,10 +64,10 @@ 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_BUG_ON_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_BUG_ON_PAGE(!PageAnonExclusive(&folio->page) &&

			VM_WARN_ON_ONCE_PAGE(!PageAnonExclusive(&folio->page) &&

					     !PageAnonExclusive(page), page);

	}

}
@@ -760,7 +760,7 @@ static struct page *follow_huge_pmd(struct vm_area_struct *vma, 
	if (!pmd_write(pmdval) && gup_must_unshare(vma, flags, page))

		return ERR_PTR(-EMLINK);



	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&

	VM_WARN_ON_ONCE_PAGE((flags & FOLL_PIN) && PageAnon(page) &&

			     !PageAnonExclusive(page), page);



	ret = try_grab_folio(page_folio(page), 1, flags);
@@ -899,7 +899,7 @@ static struct page *follow_page_pte(struct vm_area_struct *vma, 
		goto out;

	}



	VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&

	VM_WARN_ON_ONCE_PAGE((flags & FOLL_PIN) && PageAnon(page) &&

			     !PageAnonExclusive(page), page);



	/* try_grab_folio() does nothing unless FOLL_GET or FOLL_PIN is set. */
@@ -1180,7 +1180,7 @@ static int faultin_page(struct vm_area_struct *vma, 
	if (unshare) {

		fault_flags |= FAULT_FLAG_UNSHARE;

		/* FAULT_FLAG_WRITE and FAULT_FLAG_UNSHARE are incompatible */

		VM_BUG_ON(fault_flags & FAULT_FLAG_WRITE);

		VM_WARN_ON_ONCE(fault_flags & FAULT_FLAG_WRITE);

	}



	ret = handle_mm_fault(vma, address, fault_flags, NULL);
@@ -1760,10 +1760,7 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, 
		}



		/* VM_FAULT_RETRY or VM_FAULT_COMPLETED cannot return errors */

		if (!*locked) {

			BUG_ON(ret < 0);

			BUG_ON(ret >= nr_pages);

		}

		VM_WARN_ON_ONCE(!*locked && (ret < 0 || ret >= nr_pages));



		if (ret > 0) {

			nr_pages -= ret;
@@ -1808,7 +1805,6 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, 


		ret = mmap_read_lock_killable(mm);

		if (ret) {

			BUG_ON(ret > 0);

			if (!pages_done)

				pages_done = ret;

			break;
@@ -1819,11 +1815,11 @@ static __always_inline long __get_user_pages_locked(struct mm_struct *mm, 
				       pages, locked);

		if (!*locked) {

			/* Continue to retry until we succeeded */

			BUG_ON(ret != 0);

			VM_WARN_ON_ONCE(ret != 0);

			goto retry;

		}

		if (ret != 1) {

			BUG_ON(ret > 1);

			VM_WARN_ON_ONCE(ret > 1);

			if (!pages_done)

				pages_done = ret;

			break;
@@ -1885,10 +1881,10 @@ long populate_vma_page_range(struct vm_area_struct *vma, 
	int gup_flags;

	long ret;



	VM_BUG_ON(!PAGE_ALIGNED(start));

	VM_BUG_ON(!PAGE_ALIGNED(end));

	VM_BUG_ON_VMA(start < vma->vm_start, vma);

	VM_BUG_ON_VMA(end   > vma->vm_end, vma);

	VM_WARN_ON_ONCE(!PAGE_ALIGNED(start));

	VM_WARN_ON_ONCE(!PAGE_ALIGNED(end));

	VM_WARN_ON_ONCE_VMA(start < vma->vm_start, vma);

	VM_WARN_ON_ONCE_VMA(end   > vma->vm_end, vma);

	mmap_assert_locked(mm);



	/*
@@ -1957,8 +1953,8 @@ long faultin_page_range(struct mm_struct *mm, unsigned long start, 
	int gup_flags;

	long ret;



	VM_BUG_ON(!PAGE_ALIGNED(start));

	VM_BUG_ON(!PAGE_ALIGNED(end));

	VM_WARN_ON_ONCE(!PAGE_ALIGNED(start));

	VM_WARN_ON_ONCE(!PAGE_ALIGNED(end));

	mmap_assert_locked(mm);



	/*
@@ -2914,7 +2910,8 @@ static int gup_fast_pte_range(pmd_t pmd, pmd_t *pmdp, unsigned long addr, 
		} else if (pte_special(pte))

			goto pte_unmap;



		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));

		/* If it's not marked as special it must have a valid memmap. */

		VM_WARN_ON_ONCE(!pfn_valid(pte_pfn(pte)));

		page = pte_page(pte);



		folio = try_grab_folio_fast(page, 1, flags);