linux-kernel - Re: [RFC] iomap: fix race between readahead and direct write

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Message-ID: <ce4bc2f3-a23e-f6ba-0ef1-66231cd1057d@huawei.com>
Date:   Fri, 17 Jan 2020 17:39:03 +0800
From:   "yukuai (C)" <yukuai3@...wei.com>
To:     Jan Kara <jack@...e.cz>
CC:     <hch@...radead.org>, <darrick.wong@...cle.com>,
        <linux-xfs@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <houtao1@...wei.com>,
        <zhengbin13@...wei.com>, <yi.zhang@...wei.com>
Subject: Re: [RFC] iomap: fix race between readahead and direct write



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!