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mm/gup: remove (VM_)BUG_ONs

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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: David Hildenbrand <david@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: John 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2025-06-04 16:05:44 +02:00 • committed by Andrew Morton
parent 7c33c6c474
commit 792b429db7
2 changed files with 31 additions and 22 deletions
Download patch file Download diff file Expand all files Collapse all files

12
include/linux/mmdebug.h
View file

@ -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)

41
mm/gup.c
View file

@ -64,11 +64,11 @@ 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) &&
!PageAnonExclusive(page), page);
VM_WARN_ON_ONCE_PAGE(!PageAnonExclusive(&folio->page) &&
!PageAnonExclusive(page), page);
}
}
@ -760,8 +760,8 @@ 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) &&
!PageAnonExclusive(page), page);
VM_WARN_ON_ONCE_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
!PageAnonExclusive(page), page);
ret = try_grab_folio(page_folio(page), 1, flags);
if (ret)
@ -899,8 +899,8 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
goto out;
}
VM_BUG_ON_PAGE((flags & FOLL_PIN) && PageAnon(page) &&
!PageAnonExclusive(page), 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. */
ret = try_grab_folio(folio, 1, flags);
@ -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 @@ retry:
ret = mmap_read_lock_killable(mm);
if (ret) {
BUG_ON(ret > 0);
if (!pages_done)
pages_done = ret;
break;
@ -1819,11 +1815,11 @@ retry:
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);