folio_dup_file_rmap_pmd() passes PGTABLE_LEVEL_PTE to
__folio_dup_file_rmap() for HPAGE_PMD_NR pages, so it adds HPAGE_PMD_NR
PTE mappings to the folio instead of one PMD mapping. Each unmap of the
PMD removes one PMD mapping:
- the folio's mapcount never returns to zero, and removing the folio
from the page cache reports "Bad page cache", or hits a VM_BUG_ON
with CONFIG_DEBUG_VM;
- the first unmap already counts as the last one and drops the
PMD-mapped statistics while the other mm still maps the folio;
- the second one drives the entire mapcount below zero and drops them
again.
The helper has no caller yet, the next patch adds the first one. Pass
PGTABLE_LEVEL_PMD, as folio_try_dup_anon_rmap_pmd() does.
Fixes: d8ef5e311d7b ("mm/rmap: convert page_dup_file_rmap() to
folio_dup_file_rmap_[pte|ptes|pmd]()")
Signed-off-by: Konstantin Khorenko <[email protected]>
---
include/linux/rmap.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 0b332770abeed..7562017416094 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -558,7 +558,7 @@ static inline void folio_dup_file_rmap_pmd(struct folio
*folio,
struct page *page, struct vm_area_struct *dst_vma)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- __folio_dup_file_rmap(folio, page, HPAGE_PMD_NR, dst_vma,
PGTABLE_LEVEL_PTE);
+ __folio_dup_file_rmap(folio, page, HPAGE_PMD_NR, dst_vma,
PGTABLE_LEVEL_PMD);
#else
WARN_ON_ONCE(true);
#endif
--
2.43.0
