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mm: avoid endless recursion in dump_page()

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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@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov 2016-09-19 14:44:07 -07:00 committed by Linus Torvalds
parent 982785c6b0
commit 4d35427ad7
1 changed files with 4 additions and 2 deletions
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6
mm/debug.c
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@ -42,9 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
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");