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

[Christoph Hellwig]

On Tue, Jan 09, 2024 at 09:55:24AM +0000, John Garry wrote:
> So a user can issue:
>
> >xfs_io -c "atomic-writes 64K" mnt/file
> >xfs_io -c "atomic-writes" mnt/file
> [65536] mnt/file

Let me try to decipher that:

 - the first call sets a 64k fsx_atomicwrites_size size
 - the secon call queries fsx_atomicwrites_size?

> The user will still have to issue statx to get the actual atomic write 
> limit for a file, as 'xfs_io -c "atomic-writes"' does not take into account 
> any HW/linux block layer atomic write limits.

So will the set side never fail?

> Is this the sort of userspace API which you would like to see?

What I had in mind (and that's doesn't mean it's right..) was that
the user just sets a binary flag, and the fs reports the best it
could.  But there might be reasons to do it differently.