Re: [PATCH v5] generic: add a test for atomic writes

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, May 02, 2025 at 12:12:12AM -0700, Christoph Hellwig wrote:
> This fails in my zoned device tests with;
> 
> mkfs.xfs: error - cannot set blocksize 512 on block device /dev/nvme3n1: Invalid argument
> 
> that error turns to be because the scratch rtdev /dev/nvme3n1 has a 4k
> LBA size, while the main scratch device has a 512 byte sector size,
> which is a configuration common for but not exclusive to zoned device,
> and which means that we can't use a 512 byte block size for the file
> system.
> 
> I'm not really sure how to best add the case of a larger LBA size on
> the rt device to this test, though.

Me neither.  We can't write 512b blocks to the rt device obviously, but
I think the whole point of the separate "sector" size is that's the
maximum size that the fs knows it can write to the device without
tearing.

Maybe there's a way out of this: the only metadata on the realtime
volume is the rt superblock, whose size is a full fsblock.  Perhaps we
could set/validate the block size of the rt dev with the fsblock size
instead?

--D