Re: [PATCH 13/21] xfs: require file system block size alignment when using data checksums

[Christoph Hellwig <hch@lst.de>]

On Fri, Sep 25, 2026 at 04:24:56PM -0700, Darrick J. Wong wrote:
> > +	/*
> > +	 * Each checksums covers a whole file system block, and thus sub-fsblock
> > +	 * reads are not supported for file systems using data checksums.
> > +	 */
> > +	if (xfs_is_rtcsum_inode(ip))
> > +		stat->dio_read_offset_align = xfs_inode_alloc_unitsize(ip);
> 
> The allocation unit could be larger than the fsblock size, why is it
> necessary to have such large directio reads on a checksummed file?
> Though come to think of it zoned mode doesn't allow rtextsize > 1fsb
> so this question might be hair-splitting.

Exactly, allocsize is always the blocksize here.

> 
> I think you could reuse xfs_read_bounce_minsize() here.

Not a bad idea.  Let's see if our header mess allows doing that as an
inline, as doing function call for it would be a bit silly.