Re: [PATCH] mkfs: use stx_blksize for dev block size by default

[Christoph Hellwig <hch@infradead.org>]

On Thu, Feb 13, 2025 at 02:26:37PM +0100, Daniel Gomez wrote:
> That's a good question. The stx_blksize field description indicates the value
> should be referring to the fs block size that avoids RMW.

One that is optimal, the RMW is an example.  This what Posix says:

blksize_t st_blksize    A file system-specific preferred I/O block size 
                        for this object. In some file system types, this 
			may vary from file to file. 

> So I think, if devices report high values in stx_blksize, it is either because
> smaller values than the reported one cause RMW or they are incorrectly reporting
> a value in the wrong statx field.

Or it is just more efficient.  E.g. on NFS or XFS you'll get fairly
big values.

> The commit I refer in the commit message maps the minimum_io_size reported by
> the block layer with stx_blksize.

Yes, and that was my question again - minimum_io_size for block
devices is specified even more handwavy.

In other words I'm really sceptical this is going to be a net win.
To win me over you'll need to show a improvement over a wide variety
of devіces and workloads.