| From: Hugh Dickins <hughd@google.com> |
| Subject: mm,thp,rmap: subpages_mapcount of PTE-mapped subpages: fix |
| Date: Fri, 18 Nov 2022 17:35:05 -0800 (PST) |
| |
| Yu Zhao reports compiler warning in page_add_anon_rmap(): |
| |
| mm/rmap.c:1236:13: warning: variable 'first' is used uninitialized |
| whenever 'if' condition is false [-Wsometimes-uninitialized] |
| } else if (PageTransHuge(page)) { |
| ^~~~~~~~~~~~~~~~~~~ |
| mm/rmap.c:1248:18: note: uninitialized use occurs here |
| VM_BUG_ON_PAGE(!first && (flags & RMAP_EXCLUSIVE), page); |
| ^~~~~ |
| |
| We do need to fix that, even though it's only uninitialized in an |
| impossible condition: I've chosen to initialize "first" true, to |
| minimize the BUGs it might then hit; but you could just as well |
| choose to initialize it false, to maximize the BUGs it might hit. |
| |
| Link: https://lkml.kernel.org/r/7a4f5e5e-de33-dace-c526-4a3d3cf5f6e0@google.com |
| Signed-off-by: Hugh Dickins <hughd@google.com> |
| Reported-by: Yu Zhao <yuzhao@google.com> |
| Cc: "Kirill A. Shutemov" <kirill@shutemov.name> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/rmap.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/mm/rmap.c~mmthprmap-subpages_mapcount-of-pte-mapped-subpages-fix |
| +++ a/mm/rmap.c |
| @@ -1281,7 +1281,7 @@ void page_add_anon_rmap(struct page *pag |
| struct compound_mapcounts mapcounts; |
| int nr = 0, nr_pmdmapped = 0; |
| bool compound = flags & RMAP_COMPOUND; |
| - bool first; |
| + bool first = true; |
| |
| if (unlikely(PageKsm(page))) |
| lock_page_memcg(page); |
| _ |
