linux-kernel - Re: [PATCH v3 00/15] block atomic writes

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Date: Tue, 6 Feb 2024 18:44:36 +0000
From: John Garry <john.g.garry@...cle.com>
To: Christoph Hellwig <hch@....de>
Cc: axboe@...nel.dk, kbusch@...nel.org, sagi@...mberg.me, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, djwong@...nel.org, 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, ojaswin@...ux.ibm.com,
        bvanassche@....org
Subject: Re: [PATCH v3 00/15] block atomic writes

On 29/01/2024 06:18, Christoph Hellwig wrote:
> Do you have a git tree with all patches somewhere?
> 

Hi Christoph,

Please let me know if you had a chance to look at this series or what 
your plans are.

BTW, about testing, it would be good to know your thoughts on power-fail 
testing.

I have done much testing for ensuring that writes are properly issued to 
HW with no undesired splitting/merging, etc for normal operation. I have 
also tested crashing the kernel only to see if atomic writes get 
corrupted. This all looks ok.

About PF testing, I have an NVMe M.2 drive, but it supports just 4K 
nawupf. In addition, unfortunately the port on my machine does not allow 
me to power it off, so I need to plug out the power cable to test PF :(

We do also support atomic writes on our SCSI storage servers, but it is 
not practically possible to PF them.

For actual PF testing, I have been using fio in crc64 verify mode with a 
couple of tweaks to support atomic writes.

What I find from limited testing for XFS and bdev atomic writes on that 
NVMe card is that indeed 4K writes are PF-safe, but 16K (this is an 
arbitrary large block size which I chose) is not. But I think all cards 
will be 4K PF safe, even if not declared.

Thanks,
John