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Date: Wed, 28 Aug 2024 07:11:10 +0200
From: Christoph Hellwig <hch@lst.de>
To: Hongbo Li <lihongbo22@huawei.com>
Cc: ebiggers@google.com, Christian Brauner <brauner@kernel.org>, hch@lst.de,
	linux-nilfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Ryusuke Konishi <konishi.ryusuke@gmail.com>
Subject: Re: [PATCH -next] nilfs2: support STATX_DIOALIGN for statx file
Message-ID: <20240828051110.GA31869@lst.de>
References: <20240827015152.222983-1-lihongbo22@huawei.com> <CAKFNMomMtJbEbZNRAzari3koP1eRHOrUDQ=rAxDbL6yfHHG=gg@mail.gmail.com> <86e1541f-0d8b-4479-b8d1-bb5a9f5849d4@huawei.com>
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On Wed, Aug 28, 2024 at 09:12:50AM +0800, Hongbo Li wrote:
>> I checked the STATX_DIOALIGN specification while looking at the
>> implementation of other file systems, and I thought that if DIO
>> support is incomplete, the dio_xx_align member should be set to 0.
>>
>> Due to the nature of NILFS2 as a log-structured file system, DIO
>> writes fall back to buffered io.  (DIO reads are supported)
>>
> That's really a question. How to handle the asymmetric situation of 
> O_DIRECT read and write?
>
> The STATX_DIOALIGN specification does not define this case.

Yes, it needs separate reporting for the read alignment.  I actually
wrote patches for that a few days ago, but never got around to testing
them.  I'll send out what I have.