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Subject: Re: [PATCH -next 2/3] md/raid10: convert resync_lock to use seqlock
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To:     Yu Kuai <yukuai1@huaweicloud.com>, song@kernel.org
Cc:     linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org,
        yukuai3@huawei.com, yi.zhang@huawei.com
References: <20220829131502.165356-1-yukuai1@huaweicloud.com>
 <20220829131502.165356-3-yukuai1@huaweicloud.com>
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From:   Guoqing Jiang <guoqing.jiang@linux.dev>
Message-ID: <3d8859bc-80d6-08b0-fd40-8874df4d3419@linux.dev>
Date:   Fri, 2 Sep 2022 17:42:42 +0800
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Hi,

On 8/29/22 9:15 PM, Yu Kuai wrote:
> +static bool wait_barrier_nolock(struct r10conf *conf)
> +{
> +	unsigned int seq = raw_read_seqcount(&conf->resync_lock.seqcount);
> +
> +	if (seq & 1)
> +		return false;
> +
> +	if (READ_ONCE(conf->barrier))
> +		return false;
> +
> +	atomic_inc(&conf->nr_pending);
> +	if (!read_seqcount_retry(&conf->resync_lock.seqcount, seq))

I think 'seq' is usually get from read_seqcount_begin.

> +		return true;
> +
> +	atomic_dec(&conf->nr_pending);
> +	return false;
> +

Thanks,
Guoqing