Messages in this thread Patch in this message | | | Date | Fri, 18 Nov 2022 17:35:05 -0800 (PST) | From | Hugh Dickins <> | Subject | [PATCH 1/3 fix] mm,thp,rmap: subpages_mapcount of PTE-mapped subpages: fix |
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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.
Reported-by: Yu Zhao <yuzhao@google.com> Signed-off-by: Hugh Dickins <hughd@google.com> --- mm/rmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/rmap.c b/mm/rmap.c index 66be8cae640f..25b720d5ba17 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1281,7 +1281,7 @@ void page_add_anon_rmap(struct page *page, 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); -- 2.35.3
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