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Date: Thu, 21 Dec 2023 07:50:31 +0100
From: Christoph Hellwig <hch@lst.de>
To: John Garry <john.g.garry@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>, "Darrick J. Wong" <djwong@kernel.org>,
	axboe@kernel.dk, kbusch@kernel.org, sagi@grimberg.me,
	jejb@linux.ibm.com, martin.petersen@oracle.com,
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	jack@suse.cz, linux-block@vger.kernel.org,
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	ming.lei@redhat.com, jaswin@linux.ibm.com, bvanassche@acm.org
Subject: Re: [PATCH v2 00/16] block atomic writes
Message-ID: <20231221065031.GA25778@lst.de>
References: <20231212110844.19698-1-john.g.garry@oracle.com> <20231212163246.GA24594@lst.de> <b8b0a9d7-88d2-45a9-877a-ecc5e0f1e645@oracle.com> <20231213154409.GA7724@lst.de> <c729b03c-b1d1-4458-9983-113f8cd752cd@oracle.com> <20231219051456.GB3964019@frogsfrogsfrogs> <20231219052121.GA338@lst.de> <76c85021-dd9e-49e3-80e3-25a17c7ca455@oracle.com> <20231219151759.GA4468@lst.de> <fff50006-ccd2-4944-ba32-84cbb2dbd1f4@oracle.com>
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On Tue, Dec 19, 2023 at 04:53:27PM +0000, John Garry wrote:
> On 19/12/2023 15:17, Christoph Hellwig wrote:
>> On Tue, Dec 19, 2023 at 12:41:37PM +0000, John Garry wrote:
>>> How about something based on fcntl, like below? We will prob also require
>>> some per-FS flag for enabling atomic writes without HW support. That flag
>>> might be also useful for XFS for differentiating forcealign for atomic
>>> writes with just forcealign.
>> I would have just exposed it through a user visible flag instead of
>> adding yet another ioctl/fcntl opcode and yet another method.
>>
>
> Any specific type of flag?
>
> I would suggest a file attribute which we can set via chattr, but that is 
> still using an ioctl and would require a new inode flag; but at least there 
> is standard userspace support.

I'd be fine with that, but we're kinda running out of flag there.
That's why I suggested the FS_XFLAG_ instead, which basically works
the same.