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Mon, 6 Oct 2025 09:02:35 +0200 (CEST) Date: Mon, 6 Oct 2025 09:02:30 +0200 From: Boris Brezillon To: =?UTF-8?B?TG/Dr2M=?= Molinari Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Rob Herring , Steven Price , Liviu Dudau , Melissa Wen , =?UTF-8?B?TWHDrXJh?= Canal , Hugh Dickins , Baolin Wang , Andrew Morton , Al Viro , =?UTF-8?B?TWlrb8WCYWo=?= Wasiak , Christian Brauner , Nitin Gote , Andi Shyti , Christopher Healy , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org, kernel@collabora.com Subject: Re: [PATCH v3 03/10] drm/gem: Add huge tmpfs mount point helper Message-ID: <20251006090230.087021bd@fedora> In-Reply-To: <20251004093054.21388-4-loic.molinari@collabora.com> References: <20251004093054.21388-1-loic.molinari@collabora.com> <20251004093054.21388-4-loic.molinari@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 546E21C000A X-Stat-Signature: 5q9m478kf7zfqcjiiipgmigp6sjnepea X-Rspam-User: X-HE-Tag: 1759734158-592474 X-HE-Meta: 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 JA60HbpC x4zVyozBTUUHcEI0sghVi+FEiWVt4R/Jif4YPzkUT0unaS3e3TRYDL3tChhxjTAi/Qa7aBdX7hMDCVWVXJ+sCvbSrK0JEUTAgEpawJM/25ogHMrE+OpyQviVpM/6ZwW6BAl5x0kg9PLfNMA6n4F5KlKrKusV9epbePgdy/DczTnyJBiq9f3DIlS67N191QmLRBUDJhiZwOEBqE0+7xJq0jAKj2p9axH1bJWftWEtUsaNErIVJfLgOe6dboqwEXLFJ516oPHXPcwNA8ludyUBpSYM1vrJ3TEwGJzoLdM6gtVhClp6TJ0H113XB5LiAKNMJyeyNxSA4B6wrx7K30VYBoDUux1bMsYf75OAp5YfnqsCEBOcoNswWRhFUTg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sat, 4 Oct 2025 11:30:46 +0200 Lo=C3=AFc Molinari 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. >=20 > The next commits will port drivers to this helper. >=20 > v3: > - store huge tmpfs mountpoint in drm_device >=20 > Signed-off-by: Lo=C3=AFc Molinari > --- > drivers/gpu/drm/drm_gem.c | 67 +++++++++++++++++++++++++++++++++++++++ > include/drm/drm_device.h | 11 +++++++ > include/drm/drm_gem.h | 1 + > 3 files changed, 79 insertions(+) >=20 > 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 > #include > #include > +#include > #include > #include > #include > @@ -82,6 +83,72 @@ > * up at a later date, and as our interface with shmfs for memory alloca= tion. > */ > =20 > +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 =3D=3D NULL); > + > + kern_unmount(dev->huge_mnt); > + dev->huge_mnt =3D NULL; > +} > + > +/** > + * drm_gem_huge_mnt_create - Create, mount and use a huge tmpfs mountpoi= nt > + * @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 fo= r the > + * lifetime of the drm device @dev which is used at GEM object initializ= ation > + * with drm_gem_object_init(). > + * > + * The most common option value @value is "within_size" which only alloc= ates > + * huge pages if the page will be fully within the GEM object size. "alw= ays", > + * "advise" and "never" are supported too but the latter would just crea= te 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; > + > + type =3D get_fs_type("tmpfs"); > + if (unlikely(!type)) > + return -EOPNOTSUPP; > + > + if (unlikely(dev->huge_mnt)) > + return -EEXIST; Do we even care about reporting an error when the huge mount point already exists? Can we just return 0 in that case, which simplifies the call sites since they don't have to check for EEXIST anymore. > + > + fc =3D fs_context_for_mount(type, SB_KERNMOUNT); > + if (IS_ERR(fc)) > + return PTR_ERR(fc); > + ret =3D drm_gem_add_fc_param(fc, "source", "tmpfs"); > + if (unlikely(ret)) > + return -ENOPARAM; > + ret =3D drm_gem_add_fc_param(fc, "huge", value); > + if (unlikely(ret)) > + return -ENOPARAM; > + > + dev->huge_mnt =3D 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 @@ > =20 > #include > #include > +#include > #include > #include > #include > @@ -168,6 +169,16 @@ struct drm_device { > */ > struct drm_master *master; > =20 > + /** > + * @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,\ > } > =20 > +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,