linux-kernel - Re: [PATCH] mm/huge_memory: replace VM_NO_THP VM_BUG

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Date:	Mon, 4 Apr 2016 14:36:35 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Konstantin Khlebnikov <koct9i@...il.com>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Dmitry Vyukov <dvyukov@...gle.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH] mm/huge_memory: replace VM_NO_THP VM_BUG_ON with actual
 VMA check

On 04/02/2016 05:37 PM, Konstantin Khlebnikov wrote:
> Khugepaged detects own VMAs by checking vm_file and vm_ops but this
> way it cannot distinguish private /dev/zero mappings from other special
> mappings like /dev/hpet which has no vm_ops and popultes PTEs in mmap.
>
> This fixes false-positive VM_BUG_ON and prevents installing THP where
> they are not expected.
>
> Signed-off-by: Konstantin Khlebnikov <koct9i@...il.com>
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Link: http://lkml.kernel.org/r/CACT4Y+ZmuZMV5CjSFOeXviwQdABAgT7T+StKfTqan9YDtgEi5g@mail.gmail.com
> Fixes: 78f11a255749 ("mm: thp: fix /dev/zero MAP_PRIVATE and vm_flags cleanups")
> Cc: stable <stable@...r.kernel.org>

Acked-by: Vlastimil Babka <vbabka@...e.cz>