linux-kernel - Re: [PATCH v2 00/16] block atomic writes

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Date: Thu, 21 Dec 2023 07:50:31 +0100
From: Christoph Hellwig <hch@....de>
To: John Garry <john.g.garry@...cle.com>
Cc: Christoph Hellwig <hch@....de>, "Darrick J. Wong" <djwong@...nel.org>,
	axboe@...nel.dk, kbusch@...nel.org, sagi@...mberg.me,
	jejb@...ux.ibm.com, martin.petersen@...cle.com,
	viro@...iv.linux.org.uk, brauner@...nel.org, dchinner@...hat.com,
	jack@...e.cz, linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	tytso@....edu, jbongio@...gle.com, linux-scsi@...r.kernel.org,
	ming.lei@...hat.com, jaswin@...ux.ibm.com, bvanassche@....org
Subject: Re: [PATCH v2 00/16] block atomic writes

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.