Re: [PATCH v10 10/10] xfs: enable block size larger than page size support

Darrick J. Wong
2024-07-16T17:40:17Z

On Tue, Jul 16, 2024 at 04:29:05PM +0100, Matthew Wilcox wrote:
> On Mon, Jul 15, 2024 at 11:44:57AM +0200, Pankaj Raghav (Samsung) wrote:
> > +++ b/fs/xfs/xfs_super.c
> > @@ -1638,16 +1638,30 @@ xfs_fs_fill_super(
> > goto out_free_sb;
> > }
> >
> > - /*
> > - * Until this is fixed only page-sized or smaller data blocks work.
> > - */
> > if (mp->m_sb.sb_blocksize > PAGE_SIZE) {
> > - xfs_warn(mp,
> > - "File system with blocksize %d bytes. "
> > - "Only pagesize (%ld) or less will currently work.",
> > + size_t max_folio_size = mapping_max_folio_size_supported();
> > +
> > + if (!xfs_has_crc(mp)) {
> > + xfs_warn(mp,
> > +"V4 Filesystem with blocksize %d bytes. Only pagesize (%ld) or less is supported.",
> > mp->m_sb.sb_blocksize, PAGE_SIZE);
> > - error = -ENOSYS;
> > - goto out_free_sb;
> > + error = -ENOSYS;
> > + goto out_free_sb;
> > + }
> > +
> > + if (mp->m_sb.sb_blocksize > max_folio_size) {
> > + xfs_warn(mp,
> > +"block size (%u bytes) not supported; maximum folio size supported in "\
> > +"the page cache is (%ld bytes). Check MAX_PAGECACHE_ORDER (%d)",
> > + mp->m_sb.sb_blocksize, max_folio_size,
> > + MAX_PAGECACHE_ORDER);
>
> Again, too much message. Way too much. We shouldn't even allow block
> devices to be created if their block size is larger than the max supported
> by the page cache.

Filesystem blocksize != block device blocksize. xfs still needs this
check because one can xfs_copy a 64k-fsblock xfs to a hdd with 512b
sectors and try to mount that on x86.

Assuming there /is/ some fs that allows 1G blocksize, you'd then really
want a mount check that would prevent you from mounting that.

--D