The patch titled
Subject: mm: clarify why we avoid page_mapcount() for slab pages in dump_page()
has been added to the -mm tree. Its filename is
mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page.patch
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: clarify why we avoid page_mapcount() for slab pages in dump_page()
Let's add comment on why we skip page_mapcount() for sl[aou]b pages.
Link: http://lkml.kernel.org/r/20160922105532.GB24593@node
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/debug.c | 5 +++++
1 file changed, 5 insertions(+)
diff -puN mm/debug.c~mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page mm/debug.c
--- a/mm/debug.c~mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page
+++ a/mm/debug.c
@@ -42,6 +42,11 @@ const struct trace_print_flags vmaflag_n
void __dump_page(struct page *page, const char *reason)
{
+ /*
+ * Avoid VM_BUG_ON() in page_mapcount().
+ * page->_mapcount space in struct page is used by sl[aou]b pages to
+ * encode own info.
+ */
int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-clarify-why-we-avoid-page_mapcount-for-slab-pages-in-dump_page.patch
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