Re: [PATCH v7 11/11] xfs: enable block size larger than page size support

Christoph Hellwig
2024-06-17T06:51:09Z

On Mon, Jun 17, 2024 at 11:29:42AM +1000, Dave Chinner wrote:
> > > + if (mp->m_sb.sb_blocksize > PAGE_SIZE)
> > > + igeo->min_folio_order = mp->m_sb.sb_blocklog - PAGE_SHIFT;
> > > + else
> > > + igeo->min_folio_order = 0;
> > > }
> >
> > The minimum folio order isn't really part of the inode (allocation)
> > geometry, is it?
>
> I suggested it last time around instead of calculating the same
> constant on every inode allocation. We're already storing in-memory
> strunct xfs_inode allocation init values in this structure. e.g. in
> xfs_inode_alloc() we see things like this:

While new_diflags2 isn't exactly inode geometry, it at least is part
of the inode allocation. Folio min order for file data has nothing
to do with this at all.

> The only other place we might store it is the struct xfs_mount, but
> given all the inode allocation constants are already in the embedded
> mp->m_ino_geo structure, it just seems like a much better idea to
> put it will all the other inode allocation constants than dump it
> randomly into the struct xfs_mount....

Well, it is very closely elated to say the m_blockmask field in
struct xfs_mount. The again modern CPUs tend to get a you simple
subtraction for free in most pipelines doing other things, so I'm
not really sure it's worth caching for use in inode allocation to
start with, but I don't care strongly about that.