Re: [PATCH v7 06/11] drm/v3d: Use huge tmpfs mountpoint helpers

[Boris Brezillon <boris.brezillon@collabora.com>]

On Mon, 10 Nov 2025 16:49:54 +0100
Loïc Molinari <loic.molinari@collabora.com> wrote:

> Make use of the new drm_gem_huge_mnt_create() and
> drm_gem_has_huge_mnt() helpers to avoid code duplication. Now that
> it's just a few lines long, the single function in v3d_gemfs.c is
> moved into v3d_gem.c.
> 
> v3:
> - use huge tmpfs mountpoint in drm_device
> - move v3d_gemfs.c into v3d_gem.c
> 
> v4:
> - clean up mountpoint creation error handling
> 
> v5:
> - fix CONFIG_TRANSPARENT_HUGEPAGE check
> - use drm_gem_has_huge_mnt() helper
> 
> Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
> ---
>  drivers/gpu/drm/v3d/Makefile    |  3 +-
>  drivers/gpu/drm/v3d/v3d_bo.c    |  5 ++-
>  drivers/gpu/drm/v3d/v3d_drv.c   |  2 +-
>  drivers/gpu/drm/v3d/v3d_drv.h   | 11 +-----
>  drivers/gpu/drm/v3d/v3d_gem.c   | 27 ++++++++++++--
>  drivers/gpu/drm/v3d/v3d_gemfs.c | 62 ---------------------------------
>  6 files changed, 30 insertions(+), 80 deletions(-)
>  delete mode 100644 drivers/gpu/drm/v3d/v3d_gemfs.c
> 
> diff --git a/drivers/gpu/drm/v3d/Makefile b/drivers/gpu/drm/v3d/Makefile
> index fcf710926057..b7d673f1153b 100644
> --- a/drivers/gpu/drm/v3d/Makefile
> +++ b/drivers/gpu/drm/v3d/Makefile
> @@ -13,8 +13,7 @@ v3d-y := \
>  	v3d_trace_points.o \
>  	v3d_sched.o \
>  	v3d_sysfs.o \
> -	v3d_submit.o \
> -	v3d_gemfs.o
> +	v3d_submit.o
>  
>  v3d-$(CONFIG_DEBUG_FS) += v3d_debugfs.o
>  
> diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
> index d9547f5117b9..99c6a775d18b 100644
> --- a/drivers/gpu/drm/v3d/v3d_bo.c
> +++ b/drivers/gpu/drm/v3d/v3d_bo.c
> @@ -114,7 +114,7 @@ v3d_bo_create_finish(struct drm_gem_object *obj)
>  	if (IS_ERR(sgt))
>  		return PTR_ERR(sgt);
>  
> -	if (!v3d->gemfs)
> +	if (!drm_gem_has_huge_mnt(obj->dev))
>  		align = SZ_4K;
>  	else if (obj->size >= SZ_1M)
>  		align = SZ_1M;
> @@ -150,12 +150,11 @@ struct v3d_bo *v3d_bo_create(struct drm_device *dev, struct drm_file *file_priv,
>  			     size_t unaligned_size)
>  {
>  	struct drm_gem_shmem_object *shmem_obj;
> -	struct v3d_dev *v3d = to_v3d_dev(dev);
>  	struct v3d_bo *bo;
>  	int ret;
>  
>  	shmem_obj = drm_gem_shmem_create_with_mnt(dev, unaligned_size,
> -						  v3d->gemfs);
> +						  dev->huge_mnt);

I thought you needed some kind of drm_gem_huge_mnt() helper to cover
for the fact drm_device::huge_mnt does not exist if
CONFIG_TRANSPARENT_HUGEPAGE=n.


>  	if (IS_ERR(shmem_obj))
>  		return ERR_CAST(shmem_obj);
>  	bo = to_v3d_bo(&shmem_obj->base);
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.c b/drivers/gpu/drm/v3d/v3d_drv.c
> index e8a46c8bad8a..30b55a00eeda 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.c
> +++ b/drivers/gpu/drm/v3d/v3d_drv.c
> @@ -107,7 +107,7 @@ static int v3d_get_param_ioctl(struct drm_device *dev, void *data,
>  		args->value = v3d->perfmon_info.max_counters;
>  		return 0;
>  	case DRM_V3D_PARAM_SUPPORTS_SUPER_PAGES:
> -		args->value = !!v3d->gemfs;
> +		args->value = drm_gem_has_huge_mnt(dev);
>  		return 0;
>  	case DRM_V3D_PARAM_GLOBAL_RESET_COUNTER:
>  		mutex_lock(&v3d->reset_lock);
> diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h
> index 1884686985b8..99a39329bb85 100644
> --- a/drivers/gpu/drm/v3d/v3d_drv.h
> +++ b/drivers/gpu/drm/v3d/v3d_drv.h
> @@ -158,11 +158,6 @@ struct v3d_dev {
>  	struct drm_mm mm;
>  	spinlock_t mm_lock;
>  
> -	/*
> -	 * tmpfs instance used for shmem backed objects
> -	 */
> -	struct vfsmount *gemfs;
> -
>  	struct work_struct overflow_mem_work;
>  
>  	struct v3d_queue_state queue[V3D_MAX_QUEUES];
> @@ -569,6 +564,7 @@ extern const struct dma_fence_ops v3d_fence_ops;
>  struct dma_fence *v3d_fence_create(struct v3d_dev *v3d, enum v3d_queue q);
>  
>  /* v3d_gem.c */
> +extern bool super_pages;
>  int v3d_gem_init(struct drm_device *dev);
>  void v3d_gem_destroy(struct drm_device *dev);
>  void v3d_reset_sms(struct v3d_dev *v3d);
> @@ -576,11 +572,6 @@ void v3d_reset(struct v3d_dev *v3d);
>  void v3d_invalidate_caches(struct v3d_dev *v3d);
>  void v3d_clean_caches(struct v3d_dev *v3d);
>  
> -/* v3d_gemfs.c */
> -extern bool super_pages;
> -void v3d_gemfs_init(struct v3d_dev *v3d);
> -void v3d_gemfs_fini(struct v3d_dev *v3d);
> -
>  /* v3d_submit.c */
>  void v3d_job_cleanup(struct v3d_job *job);
>  void v3d_job_put(struct v3d_job *job);
> diff --git a/drivers/gpu/drm/v3d/v3d_gem.c b/drivers/gpu/drm/v3d/v3d_gem.c
> index 5a180dc6c452..f316f67364d2 100644
> --- a/drivers/gpu/drm/v3d/v3d_gem.c
> +++ b/drivers/gpu/drm/v3d/v3d_gem.c
> @@ -259,6 +259,30 @@ v3d_invalidate_caches(struct v3d_dev *v3d)
>  	v3d_invalidate_slices(v3d, 0);
>  }
>  
> +static void
> +v3d_huge_mnt_init(struct v3d_dev *v3d)
> +{
> +	int err = 0;
> +
> +	/*
> +	 * By using a huge shmemfs mountpoint when the user wants to
> +	 * enable Super Pages, we can pass in mount flags that better
> +	 * match our usecase.
> +	 */
> +
> +	if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && super_pages)
> +		err = drm_gem_huge_mnt_create(&v3d->drm, "within_size");
> +
> +	if (drm_gem_has_huge_mnt(&v3d->drm))
> +		drm_info(&v3d->drm, "Using Transparent Hugepages\n");
> +	else if (err)
> +		drm_warn(&v3d->drm, "Can't use Transparent Hugepages (%d)\n",
> +			 err);
> +	else
> +		drm_notice(&v3d->drm,
> +			   "Transparent Hugepage support is recommended for optimal performance on this platform!\n");
> +}
> +
>  int
>  v3d_gem_init(struct drm_device *dev)
>  {
> @@ -310,7 +334,7 @@ v3d_gem_init(struct drm_device *dev)
>  	v3d_init_hw_state(v3d);
>  	v3d_mmu_set_page_table(v3d);
>  
> -	v3d_gemfs_init(v3d);
> +	v3d_huge_mnt_init(v3d);
>  
>  	ret = v3d_sched_init(v3d);
>  	if (ret) {
> @@ -330,7 +354,6 @@ v3d_gem_destroy(struct drm_device *dev)
>  	enum v3d_queue q;
>  
>  	v3d_sched_fini(v3d);
> -	v3d_gemfs_fini(v3d);
>  
>  	/* Waiting for jobs to finish would need to be done before
>  	 * unregistering V3D.
> diff --git a/drivers/gpu/drm/v3d/v3d_gemfs.c b/drivers/gpu/drm/v3d/v3d_gemfs.c
> deleted file mode 100644
> index bf351fc0d488..000000000000
> --- a/drivers/gpu/drm/v3d/v3d_gemfs.c
> +++ /dev/null
> @@ -1,62 +0,0 @@
> -// SPDX-License-Identifier: GPL-2.0+
> -/* Copyright (C) 2024 Raspberry Pi */
> -
> -#include <linux/fs.h>
> -#include <linux/mount.h>
> -#include <linux/fs_context.h>
> -
> -#include <drm/drm_print.h>
> -
> -#include "v3d_drv.h"
> -
> -void v3d_gemfs_init(struct v3d_dev *v3d)
> -{
> -	struct file_system_type *type;
> -	struct fs_context *fc;
> -	struct vfsmount *gemfs;
> -	int ret;
> -
> -	/*
> -	 * By creating our own shmemfs mountpoint, we can pass in
> -	 * mount flags that better match our usecase. However, we
> -	 * only do so on platforms which benefit from it.
> -	 */
> -	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> -		goto err;
> -
> -	/* The user doesn't want to enable Super Pages */
> -	if (!super_pages)
> -		goto err;
> -
> -	type = get_fs_type("tmpfs");
> -	if (!type)
> -		goto err;
> -
> -	fc = fs_context_for_mount(type, SB_KERNMOUNT);
> -	if (IS_ERR(fc))
> -		goto err;
> -	ret = vfs_parse_fs_string(fc, "source", "tmpfs");
> -	if (!ret)
> -		ret = vfs_parse_fs_string(fc, "huge", "within_size");
> -	if (!ret)
> -		gemfs = fc_mount_longterm(fc);
> -	put_fs_context(fc);
> -	if (ret)
> -		goto err;
> -
> -	v3d->gemfs = gemfs;
> -	drm_info(&v3d->drm, "Using Transparent Hugepages\n");
> -
> -	return;
> -
> -err:
> -	v3d->gemfs = NULL;
> -	drm_notice(&v3d->drm,
> -		   "Transparent Hugepage support is recommended for optimal performance on this platform!\n");
> -}
> -
> -void v3d_gemfs_fini(struct v3d_dev *v3d)
> -{
> -	if (v3d->gemfs)
> -		kern_unmount(v3d->gemfs);
> -}