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Subject: Re: [RFC] iomap: fix race between readahead and direct write
To:     Jan Kara <jack@suse.cz>
CC:     <hch@infradead.org>, <darrick.wong@oracle.com>,
        <linux-xfs@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <houtao1@huawei.com>,
        <zhengbin13@huawei.com>, <yi.zhang@huawei.com>
References: <20200116063601.39201-1-yukuai3@huawei.com>
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From:   "yukuai (C)" <yukuai3@huawei.com>
Message-ID: <ce4bc2f3-a23e-f6ba-0ef1-66231cd1057d@huawei.com>
Date:   Fri, 17 Jan 2020 17:39:03 +0800
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On 2020/1/16 23:32, Jan Kara wrote:
> Thanks for the report and the patch. But the data integrity when mixing
> buffered and direct IO like this is best effort only. We definitely do not
> want to sacrifice performance of common cases or code complexity to make
> cases like this work reliably.

In the patch, the only thing that is diffrent is that iomap_begin() will
be called for each page. However, it seems the performance in sequential
read didn't get worse. Is there a specific case that the performance
will get worse?

Thanks!
Yu Kuai!