Add the drm_gem_huge_mnt_create() and drm_gem_get_huge_mnt() helpers
to avoid code duplication in the i915, V3D, Panfrost and Panthor
drivers. The former creates and mounts a dedicated huge tmpfs
mountpoint, for the lifetime of a DRM device, used at GEM object
initialization. The latter retrieves the dedicated huge tmpfs
mountpoint used by a DRM device.

The next commits will port drivers to these helpers.

v3:
- store huge tmpfs mountpoint in drm_device

v4:
- return 0 in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
- return 0 when huge_mnt already exists
- use new vfs_parse_fs_string() helper

v5:
- remove warning on !dev->huge_mnt and reset to NULL on free
- inline drm_gem_huge_mnt_create() to remove func from text and avoid
  calls in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
- compile out drm_device's huge_mnt field in builds with
  CONFIG_TRANSPARENT_HUGEPAGE=n
- add drm_gem_has_huge_mnt() helper

v6:
- move huge_mnt doc into ifdef'd section
- either inline or export drm_gem_huge_mnt_create()

v7:
- include <drm/drm_device.h> in drm_gem.h

v9:
- replace drm_gem_has_huge_mnt() by drm_gem_get_huge_mnt()

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
---
 drivers/gpu/drm/drm_gem.c | 57 +++++++++++++++++++++++++++++++++++++++
 include/drm/drm_device.h  | 15 +++++++++++
 include/drm/drm_gem.h     | 33 +++++++++++++++++++++++
 3 files changed, 105 insertions(+)

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index 41d344c270a7..94e5e04865ba 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -29,6 +29,9 @@
 #include <linux/export.h>
 #include <linux/file.h>
 #include <linux/fs.h>
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#include <linux/fs_context.h>
+#endif
 #include <linux/iosys-map.h>
 #include <linux/mem_encrypt.h>
 #include <linux/mm.h>
@@ -82,6 +85,60 @@
  * up at a later date, and as our interface with shmfs for memory allocation.
  */
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+static void drm_gem_huge_mnt_free(struct drm_device *dev, void *data)
+{
+	kern_unmount(dev->huge_mnt);
+}
+
+/**
+ * drm_gem_huge_mnt_create - Create, mount and use a huge tmpfs mountpoint
+ * @dev: DRM device a huge tmpfs mountpoint should be used with
+ * @value: huge tmpfs mount option value
+ *
+ * This function creates and mounts a dedicated huge tmpfs mountpoint for the
+ * lifetime of the DRM device @dev which is used at GEM object initialization
+ * with drm_gem_object_init().
+ *
+ * The most common option value @value is "within_size" which only allocates
+ * huge pages if the page will be fully within the GEM object size. "always",
+ * "advise" and "never" are supported too but the latter would just create a
+ * mountpoint similar to the default one (`shm_mnt`). See shmemfs and
+ * Transparent Hugepage for more information.
+ *
+ * Returns:
+ * 0 on success or a negative error code on failure.
+ */
+int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value)
+{
+	struct file_system_type *type;
+	struct fs_context *fc;
+	int ret;
+
+	if (unlikely(drm_gem_get_huge_mnt(dev)))
+		return 0;
+
+	type = get_fs_type("tmpfs");
+	if (unlikely(!type))
+		return -EOPNOTSUPP;
+	fc = fs_context_for_mount(type, SB_KERNMOUNT);
+	if (IS_ERR(fc))
+		return PTR_ERR(fc);
+	ret = vfs_parse_fs_string(fc, "source", "tmpfs");
+	if (unlikely(ret))
+		return -ENOPARAM;
+	ret = vfs_parse_fs_string(fc, "huge", value);
+	if (unlikely(ret))
+		return -ENOPARAM;
+
+	dev->huge_mnt = fc_mount_longterm(fc);
+	put_fs_context(fc);
+
+	return drmm_add_action_or_reset(dev, drm_gem_huge_mnt_free, NULL);
+}
+EXPORT_SYMBOL_GPL(drm_gem_huge_mnt_create);
+#endif
+
 static void
 drm_gem_init_release(struct drm_device *dev, void *ptr)
 {
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 5af49c5c3778..7dc560ad14fc 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -3,6 +3,9 @@
 
 #include <linux/list.h>
 #include <linux/kref.h>
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#include <linux/mount.h>
+#endif
 #include <linux/mutex.h>
 #include <linux/idr.h>
 #include <linux/sched.h>
@@ -168,6 +171,18 @@ struct drm_device {
 	 */
 	struct drm_master *master;
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	/**
+	 * @huge_mnt:
+	 *
+	 * Huge tmpfs mountpoint used at GEM object initialization
+	 * drm_gem_object_init(). Drivers can call drm_gem_huge_mnt_create() to
+	 * create a huge tmfps mountpoint. The default tmpfs mountpoint
+	 * (`shm_mnt`) is used if NULL.
+	 */
+	struct vfsmount *huge_mnt;
+#endif
+
 	/**
 	 * @driver_features: per-device driver features
 	 *
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 7c8bd67d087c..4e9ab5d294ac 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -40,6 +40,9 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#include <drm/drm_device.h>
+#endif
 #include <drm/drm_vma_manager.h>
 
 struct iosys_map;
@@ -492,6 +495,36 @@ struct drm_gem_object {
 		DRM_GEM_FOPS,\
 	}
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value);
+#else
+static inline int drm_gem_huge_mnt_create(struct drm_device *dev,
+					  const char *value)
+{
+	return 0;
+}
+#endif
+
+/**
+ * drm_gem_get_huge_mnt - Get the huge tmpfs mountpoint used by a DRM device
+ * @dev: DRM device
+
+ * This function gets the huge tmpfs mountpoint used by DRM device @dev. A huge
+ * tmpfs mountpoint is used after a successful call to drm_gem_huge_mnt_create()
+ * on builds with Transparent Hugepage enabled.
+
+ * Returns:
+ * The huge tmpfs mountpoint in use, NULL otherwise.
+ */
+static inline struct vfsmount *drm_gem_get_huge_mnt(struct drm_device *dev)
+{
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	return dev->huge_mnt;
+#else
+	return NULL;
+#endif
+}
+
 void drm_gem_object_release(struct drm_gem_object *obj);
 void drm_gem_object_free(struct kref *kref);
 int drm_gem_object_init(struct drm_device *dev,
-- 
2.47.3

Hi Loïc,

On 28/11/25 15:52, Loïc Molinari wrote:
> Add the drm_gem_huge_mnt_create() and drm_gem_get_huge_mnt() helpers
> to avoid code duplication in the i915, V3D, Panfrost and Panthor
> drivers. The former creates and mounts a dedicated huge tmpfs
> mountpoint, for the lifetime of a DRM device, used at GEM object
> initialization. The latter retrieves the dedicated huge tmpfs
> mountpoint used by a DRM device.
> 
> The next commits will port drivers to these helpers.
> 
> v3:
> - store huge tmpfs mountpoint in drm_device
> 
> v4:
> - return 0 in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
> - return 0 when huge_mnt already exists
> - use new vfs_parse_fs_string() helper
> 
> v5:
> - remove warning on !dev->huge_mnt and reset to NULL on free
> - inline drm_gem_huge_mnt_create() to remove func from text and avoid
>    calls in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
> - compile out drm_device's huge_mnt field in builds with
>    CONFIG_TRANSPARENT_HUGEPAGE=n
> - add drm_gem_has_huge_mnt() helper
> 
> v6:
> - move huge_mnt doc into ifdef'd section
> - either inline or export drm_gem_huge_mnt_create()
> 
> v7:
> - include <drm/drm_device.h> in drm_gem.h
> 
> v9:
> - replace drm_gem_has_huge_mnt() by drm_gem_get_huge_mnt()
> 
> Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>

Reviewed-by: Maíra Canal <mcanal@igalia.com>

Some suggestions below (feel free to ignore):

> ---
>   drivers/gpu/drm/drm_gem.c | 57 +++++++++++++++++++++++++++++++++++++++
>   include/drm/drm_device.h  | 15 +++++++++++
>   include/drm/drm_gem.h     | 33 +++++++++++++++++++++++
>   3 files changed, 105 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 41d344c270a7..94e5e04865ba 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -29,6 +29,9 @@
>   #include <linux/export.h>
>   #include <linux/file.h>
>   #include <linux/fs.h>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <linux/fs_context.h>
> +#endif
>   #include <linux/iosys-map.h>
>   #include <linux/mem_encrypt.h>
>   #include <linux/mm.h>
> @@ -82,6 +85,60 @@
>    * up at a later date, and as our interface with shmfs for memory allocation.
>    */
>   
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static void drm_gem_huge_mnt_free(struct drm_device *dev, void *data)
> +{
> +	kern_unmount(dev->huge_mnt);
> +}
> +
> +/**
> + * drm_gem_huge_mnt_create - Create, mount and use a huge tmpfs mountpoint
> + * @dev: DRM device a huge tmpfs mountpoint should be used with

Suggestion: "DRM device that will use the huge tmpfs mountpoint"

> + * @value: huge tmpfs mount option value
> + *
> + * This function creates and mounts a dedicated huge tmpfs mountpoint for the
> + * lifetime of the DRM device @dev which is used at GEM object initialization
> + * with drm_gem_object_init().
> + *
> + * The most common option value @value is "within_size" which only allocates

Suggestion: "The most common option for @value is..."

> + * huge pages if the page will be fully within the GEM object size. "always",
> + * "advise" and "never" are supported too but the latter would just create a
> + * mountpoint similar to the default one (`shm_mnt`). See shmemfs and
> + * Transparent Hugepage for more information.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */

[...]

> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 5af49c5c3778..7dc560ad14fc 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -3,6 +3,9 @@
>   
>   #include <linux/list.h>
>   #include <linux/kref.h>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <linux/mount.h>
> +#endif
>   #include <linux/mutex.h>
>   #include <linux/idr.h>
>   #include <linux/sched.h>
> @@ -168,6 +171,18 @@ struct drm_device {
>   	 */
>   	struct drm_master *master;
>   
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	/**
> +	 * @huge_mnt:
> +	 *
> +	 * Huge tmpfs mountpoint used at GEM object initialization
> +	 * drm_gem_object_init(). Drivers can call drm_gem_huge_mnt_create() to

Suggestion: "Drivers can call drm_gem_huge_mnt_create() to mount and use
it."

> +	 * create a huge tmfps mountpoint. The default tmpfs mountpoint
> +	 * (`shm_mnt`) is used if NULL.
> +	 */
> +	struct vfsmount *huge_mnt;
> +#endif
> +
>   	/**
>   	 * @driver_features: per-device driver features
>   	 *
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 7c8bd67d087c..4e9ab5d294ac 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -40,6 +40,9 @@
>   #include <linux/list.h>
>   #include <linux/mutex.h>
>   
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <drm/drm_device.h>
> +#endif
>   #include <drm/drm_vma_manager.h>
>   
>   struct iosys_map;
> @@ -492,6 +495,36 @@ struct drm_gem_object {
>   		DRM_GEM_FOPS,\
>   	}
>   
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value);
> +#else
> +static inline int drm_gem_huge_mnt_create(struct drm_device *dev,
> +					  const char *value)
> +{
> +	return 0;
> +}
> +#endif
> +
> +/**
> + * drm_gem_get_huge_mnt - Get the huge tmpfs mountpoint used by a DRM device
> + * @dev: DRM device
> +
> + * This function gets the huge tmpfs mountpoint used by DRM device @dev. A huge
> + * tmpfs mountpoint is used after a successful call to drm_gem_huge_mnt_create()

Suggestion: "A huge tmpfs is used instead of `shm_mnt` after a
successful call to drm_gem_huge_mnt_create() when
CONFIG_TRANSPARENT_HUGEPAGE is enabled"

Best Regards,
- Maíra

On Fri, 28 Nov 2025 19:52:46 +0100
Loïc Molinari <loic.molinari@collabora.com> wrote:

> Add the drm_gem_huge_mnt_create() and drm_gem_get_huge_mnt() helpers
> to avoid code duplication in the i915, V3D, Panfrost and Panthor
> drivers. The former creates and mounts a dedicated huge tmpfs
> mountpoint, for the lifetime of a DRM device, used at GEM object
> initialization. The latter retrieves the dedicated huge tmpfs
> mountpoint used by a DRM device.
> 
> The next commits will port drivers to these helpers.
> 
> v3:
> - store huge tmpfs mountpoint in drm_device
> 
> v4:
> - return 0 in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
> - return 0 when huge_mnt already exists
> - use new vfs_parse_fs_string() helper
> 
> v5:
> - remove warning on !dev->huge_mnt and reset to NULL on free
> - inline drm_gem_huge_mnt_create() to remove func from text and avoid
>   calls in builds with CONFIG_TRANSPARENT_HUGEPAGE=n
> - compile out drm_device's huge_mnt field in builds with
>   CONFIG_TRANSPARENT_HUGEPAGE=n
> - add drm_gem_has_huge_mnt() helper
> 
> v6:
> - move huge_mnt doc into ifdef'd section
> - either inline or export drm_gem_huge_mnt_create()
> 
> v7:
> - include <drm/drm_device.h> in drm_gem.h
> 
> v9:
> - replace drm_gem_has_huge_mnt() by drm_gem_get_huge_mnt()
> 
> Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>

> ---
>  drivers/gpu/drm/drm_gem.c | 57 +++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_device.h  | 15 +++++++++++
>  include/drm/drm_gem.h     | 33 +++++++++++++++++++++++
>  3 files changed, 105 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 41d344c270a7..94e5e04865ba 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -29,6 +29,9 @@
>  #include <linux/export.h>
>  #include <linux/file.h>
>  #include <linux/fs.h>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <linux/fs_context.h>
> +#endif
>  #include <linux/iosys-map.h>
>  #include <linux/mem_encrypt.h>
>  #include <linux/mm.h>
> @@ -82,6 +85,60 @@
>   * up at a later date, and as our interface with shmfs for memory allocation.
>   */
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +static void drm_gem_huge_mnt_free(struct drm_device *dev, void *data)
> +{
> +	kern_unmount(dev->huge_mnt);
> +}
> +
> +/**
> + * drm_gem_huge_mnt_create - Create, mount and use a huge tmpfs mountpoint
> + * @dev: DRM device a huge tmpfs mountpoint should be used with
> + * @value: huge tmpfs mount option value
> + *
> + * This function creates and mounts a dedicated huge tmpfs mountpoint for the
> + * lifetime of the DRM device @dev which is used at GEM object initialization
> + * with drm_gem_object_init().
> + *
> + * The most common option value @value is "within_size" which only allocates
> + * huge pages if the page will be fully within the GEM object size. "always",
> + * "advise" and "never" are supported too but the latter would just create a
> + * mountpoint similar to the default one (`shm_mnt`). See shmemfs and
> + * Transparent Hugepage for more information.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value)
> +{
> +	struct file_system_type *type;
> +	struct fs_context *fc;
> +	int ret;
> +
> +	if (unlikely(drm_gem_get_huge_mnt(dev)))
> +		return 0;
> +
> +	type = get_fs_type("tmpfs");
> +	if (unlikely(!type))
> +		return -EOPNOTSUPP;
> +	fc = fs_context_for_mount(type, SB_KERNMOUNT);
> +	if (IS_ERR(fc))
> +		return PTR_ERR(fc);
> +	ret = vfs_parse_fs_string(fc, "source", "tmpfs");
> +	if (unlikely(ret))
> +		return -ENOPARAM;
> +	ret = vfs_parse_fs_string(fc, "huge", value);
> +	if (unlikely(ret))
> +		return -ENOPARAM;
> +
> +	dev->huge_mnt = fc_mount_longterm(fc);
> +	put_fs_context(fc);
> +
> +	return drmm_add_action_or_reset(dev, drm_gem_huge_mnt_free, NULL);
> +}
> +EXPORT_SYMBOL_GPL(drm_gem_huge_mnt_create);
> +#endif
> +
>  static void
>  drm_gem_init_release(struct drm_device *dev, void *ptr)
>  {
> diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
> index 5af49c5c3778..7dc560ad14fc 100644
> --- a/include/drm/drm_device.h
> +++ b/include/drm/drm_device.h
> @@ -3,6 +3,9 @@
>  
>  #include <linux/list.h>
>  #include <linux/kref.h>
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <linux/mount.h>
> +#endif
>  #include <linux/mutex.h>
>  #include <linux/idr.h>
>  #include <linux/sched.h>
> @@ -168,6 +171,18 @@ struct drm_device {
>  	 */
>  	struct drm_master *master;
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	/**
> +	 * @huge_mnt:
> +	 *
> +	 * Huge tmpfs mountpoint used at GEM object initialization
> +	 * drm_gem_object_init(). Drivers can call drm_gem_huge_mnt_create() to
> +	 * create a huge tmfps mountpoint. The default tmpfs mountpoint
> +	 * (`shm_mnt`) is used if NULL.
> +	 */
> +	struct vfsmount *huge_mnt;
> +#endif
> +
>  	/**
>  	 * @driver_features: per-device driver features
>  	 *
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index 7c8bd67d087c..4e9ab5d294ac 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -40,6 +40,9 @@
>  #include <linux/list.h>
>  #include <linux/mutex.h>
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +#include <drm/drm_device.h>
> +#endif
>  #include <drm/drm_vma_manager.h>
>  
>  struct iosys_map;
> @@ -492,6 +495,36 @@ struct drm_gem_object {
>  		DRM_GEM_FOPS,\
>  	}
>  
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value);
> +#else
> +static inline int drm_gem_huge_mnt_create(struct drm_device *dev,
> +					  const char *value)
> +{
> +	return 0;
> +}
> +#endif
> +
> +/**
> + * drm_gem_get_huge_mnt - Get the huge tmpfs mountpoint used by a DRM device
> + * @dev: DRM device
> +
> + * This function gets the huge tmpfs mountpoint used by DRM device @dev. A huge
> + * tmpfs mountpoint is used after a successful call to drm_gem_huge_mnt_create()
> + * on builds with Transparent Hugepage enabled.
> +
> + * Returns:
> + * The huge tmpfs mountpoint in use, NULL otherwise.
> + */
> +static inline struct vfsmount *drm_gem_get_huge_mnt(struct drm_device *dev)
> +{
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	return dev->huge_mnt;
> +#else
> +	return NULL;
> +#endif
> +}
> +
>  void drm_gem_object_release(struct drm_gem_object *obj);
>  void drm_gem_object_free(struct kref *kref);
>  int drm_gem_object_init(struct drm_device *dev,