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

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Date: Tue, 19 Dec 2023 16:53:27 +0000
From: John Garry <john.g.garry@...cle.com>
To: Christoph Hellwig <hch@....de>
Cc: "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 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.

> And yes, for anything that doesn't always support atomic writes it would
> need to be persisted.