Re: [PATCH] mm: thp: Deny THP for guest_memfd and secretmem in file_thp_enabled()

[Deepanshu Kartikey <kartikey406@gmail.com>]

On Tue, Feb 10, 2026 at 1:43 AM David Hildenbrand (Arm)
<david@kernel.org> wrote:
>

> The following is a bit nasty as well but should do the trick until we rip
> out the CONFIG_READ_ONLY_THP_FOR_FS stuff.
>
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 03886d4ccecc..4ac1cb36b861 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -40,6 +40,7 @@
>   #include <linux/pgalloc.h>
>   #include <linux/pgalloc_tag.h>
>   #include <linux/pagewalk.h>
> +#include <linux/secretmem.h>
>
>   #include <asm/tlb.h>
>   #include "internal.h"
> @@ -94,6 +95,10 @@ static inline bool file_thp_enabled(struct vm_area_struct *vma)
>
>          inode = file_inode(vma->vm_file);
>
> +       if (mapping_inaccessible(inode->i_mapping) ||
> +           secretmem_mapping(inode->i_mapping))
> +               return false;
> +
>          return !inode_is_open_for_write(inode) && S_ISREG(inode->i_mode);
>   }
>
>

Hi David,

Agreed, using mapping_inaccessible() for guest_memfd and
secretmem_mapping() for secretmem is much simpler than introducing a
new AS flag. No changes needed outside of file_thp_enabled().

I will send a v2 with your suggested diff and test it on syzbot.

Thanks,
Deepanshu