The patch titled
Subject: mm: avoid endless recursion in dump_page()
has been added to the -mm tree. Its filename is
mm-avoid-endless-recursion-in-dump_page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-avoid-endless-recursion-in-dump_page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-avoid-endless-recursion-in-dump_page.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: avoid endless recursion in dump_page()
dump_page() uses page_mapcount() to get mapcount of the page.
page_mapcount() has VM_BUG_ON_PAGE(PageSlab(page)) as mapcount doesn't
make sense for slab pages and the field in struct page used for other
information.
It leads to recursion if dump_page() called for slub page and DEBUG_VM
is enabled:
dump_page() -> page_mapcount() -> VM_BUG_ON_PAGE() -> dump_page -> ...
Let's avoid calling page_mapcount() for slab pages in dump_page().
Link: http://lkml.kernel.org/r/20160908082137.131076-1-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff -puN mm/debug.c~mm-avoid-endless-recursion-in-dump_page mm/debug.c
--- a/mm/debug.c~mm-avoid-endless-recursion-in-dump_page
+++ a/mm/debug.c
@@ -42,9 +42,11 @@ const struct trace_print_flags vmaflag_n
void __dump_page(struct page *page, const char *reason)
{
+ int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
+
pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
- page, page_ref_count(page), page_mapcount(page),
- page->mapping, page->index);
+ page, page_ref_count(page), mapcount,
+ page->mapping, page_to_pgoff(page));
if (PageCompound(page))
pr_cont(" compound_mapcount: %d", compound_mapcount(page));
pr_cont("\n");
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
khugepaged-fix-use-after-free-in-collapse_huge_page.patch
mm-avoid-endless-recursion-in-dump_page.patch
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