Re: [PATCH v2] mm: shmem: don't set large-order range for internal shmem mount

[Matthew Wilcox]

On Wed, Apr 15, 2026 at 04:22:53PM +0800, Baolin Wang wrote:
> +	/*
> +	 * Only set the large order range for tmpfs mounts. The large order
> +	 * selection for the internal shmem mount is configured dynamically
> +	 * via the 'shmem_enabled' interfaces, so there is no need to set a
> +	 * large order range for the internal shmem mount's mapping.
> +	 *
> +	 * Note: Don't consider 'deny' for emergencies and 'force' for
> +	 * testing.
> +	 */
> +	if (sbinfo->huge && !(sb->s_flags & SB_KERNMOUNT))
>  		mapping_set_large_folios(inode->i_mapping);

This isn't how mapping_set_large_folios() is supposed to be used.
It's supposed to indicate "does the filesystem support large folios".
shmem should be setting it unconditionally and if there needs to be some
other way to prevent large folios from being created, we should do that
instead.

The current code is wrong too.