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

["Loïc Molinari" <loic.molinari@collabora.com>]

On 12/11/2025 10:25, Boris Brezillon wrote:
> 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.

Ah right. For this one in v8, I've just added a temporary ifdef that 
gets removed in the next commit while getting rif of the *_with_mnt 
functions.

> 
>>   	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);
>> -}
>