The patch titled
Subject: mm,thp,rmap: subpages_mapcount of PTE-mapped subpages: fix
has been added to the -mm mm-unstable branch. Its filename is
mmthprmap-subpages_mapcount-of-pte-mapped-subpages-fix.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmthprmap-subpages_mapcount-of-pte-mapped-subpages-fix.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
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@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reported-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mmhugetlb-use-folio-fields-in-second-tail-page.patch
mmhugetlb-use-folio-fields-in-second-tail-page-fix.patch
mmthprmap-simplify-compound-page-mapcount-handling.patch
mmthprmap-lock_compound_mapcounts-on-thp-mapcounts.patch
mmthprmap-handle-the-normal-pagecompound-case-first.patch
mmthprmap-subpages_mapcount-of-pte-mapped-subpages.patch
mmthprmap-subpages_mapcount-of-pte-mapped-subpages-fix.patch
mmthprmap-subpages_mapcount-compound_mapped-if-pmd-mapped.patch
mmthprmap-clean-up-the-end-of-__split_huge_pmd_locked.patch
