mm: thp: avoid false positive VM_BUG_ON_PAGE in page_move_anon_rmap()

If page_move_anon_rmap() is refiling a pmd-splitted THP mapped in a tail page from a pte, the "address" must be THP aligned in order for the page->index bugcheck to pass in the CONFIG_DEBUG_VM=y builds. Link: http://lkml.kernel.org/r/1464253620-106404-1-git-send-email-kirill.shutemov@linux.intel.com Fixes: 6d0a07e ("mm: thp: calculate the mapcount correctly for THP pages during WP faults") Signed-off-by: Kirill A. Shutemov <[email protected]> Reported-by: Mika Westerberg <[email protected]> Tested-by: Mika Westerberg <[email protected]> Reviewed-by: Andrea Arcangeli <[email protected]> Cc: <[email protected]> [4.5] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
akeromi · May 27, 2016 · 0798d3c · 0798d3c
1 parent e2fe145
commit 0798d3c
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/mm/rmap.c b/mm/rmap.c
@@ -1098,6 +1098,8 @@ void page_move_anon_rmap(struct page *page,
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
 	VM_BUG_ON_VMA(!anon_vma, vma);
+	if (IS_ENABLED(CONFIG_DEBUG_VM) && PageTransHuge(page))
+		address &= HPAGE_PMD_MASK;
 	VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
 
 	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;