From: Michal Hocko <mhocko@kernel.org>
To: Wang Xiaoqiang <wang_xiaoq@126.com>
Cc: vbabka@suse.cz, n-horiguchi@ah.jp.nec.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: Question About Functions "__free_pages_check" and "check_new_page" in page_alloc.c
Date: Mon, 16 May 2016 17:16:57 +0200 [thread overview]
Message-ID: <20160516151657.GC23251@dhcp22.suse.cz> (raw)
In-Reply-To: <7374bd2e.da35.154b9cda7d2.Coremail.wang_xiaoq@126.com>
On Mon 16-05-16 21:42:23, Wang Xiaoqiang wrote:
> Hi all,
>
> I am really confused about these two functions. The following code snippet:
>
> if(unlikely(atomic_read(&page->_mapcount) != -1))
> bad_reason ="nonzero mapcount";if(unlikely(page->mapping != NULL))
> bad_reason ="non-NULL mapping";if(unlikely(page_ref_count(page) !=0))
> bad_reason ="nonzero _count";
> ...
> Wouldn't the previous value of "bad_reason" be overwritten by
> the later? Hope to receive from you.
yes it would. Why that would matter. The checks should be in an order
which could give us a more specific reason with later checks. bad_page()
will then print more detailed information.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-05-16 15:17 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-16 13:42 Wang Xiaoqiang
2016-05-16 15:16 ` Michal Hocko [this message]
2016-05-17 1:06 ` Wang Xiaoqiang
2016-05-17 5:14 ` Vlastimil Babka
2016-05-17 8:17 ` Wang Xiaoqiang
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