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Subject: Re: [PATCH] fix page_count in ->iomap_migrate_page()
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From: Gao Xiang <hsiangkao@aol.com>
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Date: Fri, 14 Dec 2018 21:55:01 +0800
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To: Richard Weinberger <richard@nod.at>
Cc: Artem Bityutskiy <dedekind1@gmail.com>, zhangjun <openzhangj@gmail.com>, Alexander Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, "Darrick J . Wong" <darrick.wong@oracle.com>, hch@lst.de, bfoster@redhat.com, Dave Chinner <david@fromorbit.com>, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, mhocko@suse.com, n-horiguchi@ah.jp.nec.com, mgorman@techsingularity.net, aarcange@redhat.com, willy@infradead.org, linux@dominikbrodowski.net, linux-mm@kvack.org, Gao Xiang <gaoxiang25@huawei.com>

Hi Richard,

On 2018/12/14 21:35, Richard Weinberger wrote:
> Hmm, in case of UBIFS it seems easy. We can add a get/put_page() around setting/clearing
> the flag.
> I did that now and so far none of my tests exploded.

Yes, many existed codes are based on this restriction in order to be freeable race-free.
and that's it since PG_Private was once introduced at first by Andrew Morton in 2002
for many Linux versions....and it's not bad I think... :)

Thanks,
Gao Xiang