Re: [PATCH 03/21] fs/bdev: Add atomic write support info to statx

Christoph Hellwig
2023-11-09T15:15:39Z

On Mon, Oct 02, 2023 at 08:28:04PM -0400, Martin K. Petersen wrote:
>
> Bart,
>
> > Neither the SCSI SBC standard nor the NVMe standard defines a "minimum
> > atomic write unit". So why to introduce something in the Linux kernel
> > that is not defined in common storage standards?
>
> >From SBC-5:
>
> "The ATOMIC TRANSFER LENGTH GRANULARITY field indicates the minimum
> transfer length for an atomic write command."

I would suggest that we don't try to claim any atomic write capability
if this is not a logical block as such devices are completely useless.
In fact I'd add a big warning to the kernel log if a device claims this,
as this breaks all the implicit assumptions that a single logical
block write is atomic.