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", _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
