linux-kernel - [PATCH 0/2] Reintroduce picky __compound_tail

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Date:	Tue, 28 Apr 2015 19:24:56 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrea Arcangeli <aarcange@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Hugh Dickins <hughd@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 0/2] Reintroduce picky __compound_tail_refcounted()

Hi Andrew,

My patch 8d63d99a5dfb which was merged during 4.1 merge window caused
regression:

  page:ffffea0010a15040 count:0 mapcount:1 mapping:          (null) index:0x0
  flags: 0x8000000000008014(referenced|dirty|tail)
  page dumped because: VM_BUG_ON_PAGE(page_mapcount(page) != 0)
  ------------[ cut here ]------------
  kernel BUG at mm/swap.c:134!

The patch was reverted by Linus.

This VM_BUG_ON_PAGE() is bogus. The first patch explains why the assert is
wrong and removes it. The second re-introduces original patch.

Kirill A. Shutemov (2):
  mm: drop bogus VM_BUG_ON_PAGE assert in put_page() codepath
  mm: avoid tail page refcounting on non-THP compound pages

 include/linux/mm.h | 2 +-
 mm/swap.c          | 1 -
 2 files changed, 1 insertion(+), 2 deletions(-)

-- 
2.1.4

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