From: "Pratyush Yadav (Google)" <pratyush@kernel.org>

The Live Update Orchestrator's (LUO) memfd preservation works by
preserving all the folios of a memfd, re-creating an empty memfd on the
next boot, and then inserting back the preserved folios.

Currently it creates the file by directly calling shmem_file_setup().
This leaves out other work done by alloc_file() like setting up the file
mode, flags, or calling the security hooks.

Export alloc_file() to let memfd_luo use it. Rename it to
memfd_alloc_file() since it is no longer private and thus needs a
subsystem prefix.

Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
---
 include/linux/memfd.h | 6 ++++++
 mm/memfd.c            | 4 ++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/linux/memfd.h b/include/linux/memfd.h
index cc74de3dbcfe..c328a7b356d0 100644
--- a/include/linux/memfd.h
+++ b/include/linux/memfd.h
@@ -17,6 +17,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx);
  * to by vm_flags_ptr.
  */
 int memfd_check_seals_mmap(struct file *file, vm_flags_t *vm_flags_ptr);
+struct file *memfd_alloc_file(const char *name, unsigned int flags);
 #else
 static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned int a)
 {
@@ -31,6 +32,11 @@ static inline int memfd_check_seals_mmap(struct file *file,
 {
 	return 0;
 }
+
+static inline struct file *memfd_alloc_file(const char *name, unsigned int flags)
+{
+	return ERR_PTR(-EINVAL);
+}
 #endif
 
 #endif /* __LINUX_MEMFD_H */
diff --git a/mm/memfd.c b/mm/memfd.c
index ab5312aff14b..f032c6052926 100644
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -456,7 +456,7 @@ static char *alloc_name(const char __user *uname)
 	return ERR_PTR(error);
 }
 
-static struct file *alloc_file(const char *name, unsigned int flags)
+struct file *memfd_alloc_file(const char *name, unsigned int flags)
 {
 	unsigned int *file_seals;
 	struct file *file;
@@ -520,5 +520,5 @@ SYSCALL_DEFINE2(memfd_create,
 		return PTR_ERR(name);
 
 	fd_flags = (flags & MFD_CLOEXEC) ? O_CLOEXEC : 0;
-	return FD_ADD(fd_flags, alloc_file(name, flags));
+	return FD_ADD(fd_flags, memfd_alloc_file(name, flags));
 }
-- 
2.52.0.457.g6b5491de43-goog

> ---
>  include/linux/memfd.h | 6 ++++++
>  mm/memfd.c            | 4 ++--
>  2 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/memfd.h b/include/linux/memfd.h
> index cc74de3dbcfe..c328a7b356d0 100644
> --- a/include/linux/memfd.h
> +++ b/include/linux/memfd.h
> @@ -17,6 +17,7 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx);
>   * to by vm_flags_ptr.
>   */
>  int memfd_check_seals_mmap(struct file *file, vm_flags_t *vm_flags_ptr);
> +struct file *memfd_alloc_file(const char *name, unsigned int flags);
>  #else
>  static inline long memfd_fcntl(struct file *f, unsigned int c, unsigned int a)
>  {
> @@ -31,6 +32,11 @@ static inline int memfd_check_seals_mmap(struct file *file,
>  {
>         return 0;
>  }
> +
> +static inline struct file *memfd_alloc_file(const char *name, unsigned int flags)
> +{
> +       return ERR_PTR(-EINVAL);
> +}
>  #endif
>
>  #endif /* __LINUX_MEMFD_H */
> diff --git a/mm/memfd.c b/mm/memfd.c
> index ab5312aff14b..f032c6052926 100644
> --- a/mm/memfd.c
> +++ b/mm/memfd.c
> @@ -456,7 +456,7 @@ static char *alloc_name(const char __user *uname)
>         return ERR_PTR(error);
>  }
>
> -static struct file *alloc_file(const char *name, unsigned int flags)
> +struct file *memfd_alloc_file(const char *name, unsigned int flags)
>  {
>         unsigned int *file_seals;
>         struct file *file;
> @@ -520,5 +520,5 @@ SYSCALL_DEFINE2(memfd_create,
>                 return PTR_ERR(name);
>
>         fd_flags = (flags & MFD_CLOEXEC) ? O_CLOEXEC : 0;
> -       return FD_ADD(fd_flags, alloc_file(name, flags));
> +       return FD_ADD(fd_flags, memfd_alloc_file(name, flags));
>  }

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>

On Thu, Jan 22, 2026 at 04:18:39PM +0100, Pratyush Yadav wrote:
> From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
> 
> The Live Update Orchestrator's (LUO) memfd preservation works by
> preserving all the folios of a memfd, re-creating an empty memfd on the
> next boot, and then inserting back the preserved folios.
> 
> Currently it creates the file by directly calling shmem_file_setup().
> This leaves out other work done by alloc_file() like setting up the file
> mode, flags, or calling the security hooks.
> 
> Export alloc_file() to let memfd_luo use it. Rename it to
> memfd_alloc_file() since it is no longer private and thus needs a
> subsystem prefix.
> 
> Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

-- 
Sincerely yours,
Mike.