On Sat, 4 Oct 2025 11:30:46 +0200 Loïc Molinari <[email protected]> wrote:
> Add the drm_gem_huge_mnt_create() helper to avoid code duplication in > the i915, V3D, Panfrost and Panthor drivers. It creates and mounts a > dedicated huge tmpfs mountpoint, for the lifetime of a drm device, > used at GEM object initialization. > > The next commits will port drivers to this helper. > > v3: > - store huge tmpfs mountpoint in drm_device > > Signed-off-by: Loïc Molinari <[email protected]> > --- > drivers/gpu/drm/drm_gem.c | 67 +++++++++++++++++++++++++++++++++++++++ > include/drm/drm_device.h | 11 +++++++ > include/drm/drm_gem.h | 1 + > 3 files changed, 79 insertions(+) > > diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c > index f5a10ff363c9..b4e4947210ef 100644 > --- a/drivers/gpu/drm/drm_gem.c > +++ b/drivers/gpu/drm/drm_gem.c > @@ -29,6 +29,7 @@ > #include <linux/export.h> > #include <linux/file.h> > #include <linux/fs.h> > +#include <linux/fs_context.h> > #include <linux/iosys-map.h> > #include <linux/mem_encrypt.h> > #include <linux/mm.h> > @@ -82,6 +83,72 @@ > * up at a later date, and as our interface with shmfs for memory allocation. > */ > > +static int drm_gem_add_fc_param(struct fs_context *fc, const char *key, > + const char *value) > +{ > + return vfs_parse_fs_string(fc, key, value, strlen(value)); > +} > + > +static void drm_gem_huge_mnt_free(struct drm_device *dev, void *data) > +{ > + drm_WARN_ON(dev, dev->huge_mnt == NULL); > + > + kern_unmount(dev->huge_mnt); > + dev->huge_mnt = NULL; > +} > + > +/** > + * 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. Returns -EEXIST if > called > + * more than once for the lifetime of the drm device. > + */ > +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 (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) > + return -EOPNOTSUPP; If we return 0 here, we can get rid of the if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) tests in all the drivers and let them call drm_gem_huge_mnt_create() unconditionally. > + > + type = get_fs_type("tmpfs"); > + if (unlikely(!type)) > + return -EOPNOTSUPP; > + > + if (unlikely(dev->huge_mnt)) > + return -EEXIST; > + > + fc = fs_context_for_mount(type, SB_KERNMOUNT); > + if (IS_ERR(fc)) > + return PTR_ERR(fc); > + ret = drm_gem_add_fc_param(fc, "source", "tmpfs"); > + if (unlikely(ret)) > + return -ENOPARAM; > + ret = drm_gem_add_fc_param(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); > + > 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 59fd3f4d5995..895b0ced972e 100644 > --- a/include/drm/drm_device.h > +++ b/include/drm/drm_device.h > @@ -3,6 +3,7 @@ > > #include <linux/list.h> > #include <linux/kref.h> > +#include <linux/mount.h> > #include <linux/mutex.h> > #include <linux/idr.h> > #include <linux/sched.h> > @@ -168,6 +169,16 @@ struct drm_device { > */ > struct drm_master *master; > > + /** > + * @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; > + > /** > * @driver_features: per-device driver features > * > diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h > index 7c8bd67d087c..7285a62d9afc 100644 > --- a/include/drm/drm_gem.h > +++ b/include/drm/drm_gem.h > @@ -492,6 +492,7 @@ struct drm_gem_object { > DRM_GEM_FOPS,\ > } > > +int drm_gem_huge_mnt_create(struct drm_device *dev, const char *value); > 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,
