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

[David Hildenbrand (Arm)]

On 2/10/26 02:51, Deepanshu Kartikey wrote:
> On Tue, Feb 10, 2026 at 1:43 AM David Hildenbrand (Arm)
> <david@xxxxxxxxxx> 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.

Let's wait a bit until we are in agreement that this is the right thing 
to do :)

--
Cheers,

David