Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   =?UTF-8?q?Micha=C5=82=20Winiarski?= <michal.winiarski@intel.com>
To:     <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
        <intel-gfx@lists.freedesktop.org>
CC:     David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
        "Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Simon Ser <contact@emersion.fr>,
        Matthew Wilcox <willy@infradead.org>,
        =?UTF-8?q?Micha=C5=82=20Winiarski?= <michal.winiarski@intel.com>
Subject: [PATCH v5 1/3] drm: Use XArray instead of IDR for minors
Date:   Sun, 11 Sep 2022 23:14:41 +0200
Message-ID: <20220911211443.581481-2-michal.winiarski@intel.com>
In-Reply-To: <20220911211443.581481-1-michal.winiarski@intel.com>
References: <20220911211443.581481-1-michal.winiarski@intel.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?Q215V2NqS2w4b3BJVGpDYmhSZnp2Vklra0RxeWdjN25YL1VtcVRLVFR1RmxS?=
 =?utf-8?B?TER1Sm5QcmxHQzZXODUvSmc2eXdIei9uTVA2UnVKT0ZVWVlhbEJ2bHNYc1Jo?=
 =?utf-8?B?TXZROUltbElUMFNwbjd1MUpNTG1kRitaSmh1bDBxOWhzcHlQNHp5b2tUZ3Bm?=
 =?utf-8?B?NXhwMU9QVVdQcXlEMTJFOE9YQU0xcWxFOUtoazJBZDE3WE93SCtPTHFPWklB?=
 =?utf-8?B?REREakFuK0lYTFJPdXdlSlBXSDJObktWWGthYTZuQkZheTNwU3c2WkhNMG1m?=
 =?utf-8?B?bnlFWVdwU0hvWXo1RUYvaE1zUTVxVk1RWnlqa1Jja24raldHblEyTmNicnF4?=
 =?utf-8?B?MjFxQjlSK0U4VjFzZ3dISFEzVnVuN25XN2J2MitSdks5akRiU3BKNHg5M1Z3?=
 =?utf-8?B?VmtvSlJmM3lWeXQvaVYwYW11aEMvRjFUY1NxejZYczNJanFpdlBJODBXM05p?=
 =?utf-8?B?dW1ZOGlLckVZTnZlY1hWMFNwOUVOb2J6MzBTVWVvSXJZNnhSS0RpTDMrd1hx?=
 =?utf-8?B?Mkh6NEFGY0FRM0dhVzZvYlQwWFAveVI1U1RsS2hteWs1RWVyZ21FSGtHSWd3?=
 =?utf-8?B?bGRWOWxPcWFRdHhDTUtvLzRIUmYweW1EYjhlckFYOVFVRkFzNjlRVlZUd3Vz?=
 =?utf-8?B?QWZmZlpBL3dvNmJzd28zRjRiZnFGb0I1b2pNTE5YN3hyTWtESXpJL3VUWGJp?=
 =?utf-8?B?ZlRGalhxQTNIYXZET0IrMXVGM0ttMS9sRFoxMFV3Ukl1eS9KbkwrU3JoSmlm?=
 =?utf-8?B?eUtMMXZzaTRaZGF1SmhucTVINVlnUnY5R094WU1mSjdUWVNGZmZYOEJyL3Fy?=
 =?utf-8?B?cENvUUcwaTNKZzR3cHBsSmd5blY5cFcyMWFuc0lTS0E1Nnp4K3ZlVjRaajVh?=
 =?utf-8?B?TC9Wa3ROUnVweUtOK2dVVzZEWWJ3Yzg1ZXRJVWhRYmpNZEJQNVNxb01TYStj?=
 =?utf-8?B?MmY0S1YvOFRRQ1N5c0p2N241N3FBejFrWU1XRS9ad0g5NkdsSDdkQ3k1ODJi?=
 =?utf-8?B?VE8xbFoyU293OEtuUjdCWkx6K1hHaERiSXdYbWtEMThPQTRXMXhMNDNERjI2?=
 =?utf-8?B?WGxwdXJqMndHU0kwU2JLTm9NSDJDVzhRRmVaOXpxSDBiUW5iWnoycVdNSEx0?=
 =?utf-8?B?N2dzQUVFd3dmMEFXTG5Ub0JVRXlERVBPekxOdU1VaEI0U2EzaE15M3JZZXFX?=
 =?utf-8?B?VmtjSnhFaW44YTUrNnNzUTZrZHJqa2oxUTNweEdxZW5NRDlsYnJWdE0yTE5o?=
 =?utf-8?B?RU1nK0F5UG1Qb0NRMGdXQ0h6WjNvbjd4QWpVK0tCbUNER3o1eUY4eGZzcU50?=
 =?utf-8?B?TXo1eUFtMlEvV0dYdlEwRW1lVFNyYlNXRkFINVBTUUJVWWVBelVNdzh3SmFn?=
 =?utf-8?B?THZDaTU1ME9KeExnajdRUUJqMzRpY2RVamx0L3RKOGFIenNHcDFOWTBlS0Zy?=
 =?utf-8?B?OXluamZPMEVjZEdhMG5uTXM2V1kwWmIwbENsYjVnbmNhMWc3MFBYeEJ2c2E4?=
 =?utf-8?B?ZU9kcndWdkFLTzVGN1dkQmRha1pnWFM2WjA5YnZNajV5MWFUQ2dNcVNZeW16?=
 =?utf-8?B?RjluRmo3TEVzTFR5bEVBdGtsTTBZMXpacGxoUDdLbkJqTDhXanBpeFFlRDkv?=
 =?utf-8?B?cWRjZ1ZKMUxNSnpsaEZyaVJYc0RHdG5FeGtEcW85SFpFMFoyRXMxbVAwYnFR?=
 =?utf-8?B?YlFiTUtWTU5LclZlY2YrUzZ0VUMrYURkZEVrN0xxOXVxN2VZYlRYaGVSVFJ1?=
 =?utf-8?B?bWpscitqWForSGVmVzRkc2VUMGFRNVpHZVNmSnlUVi9Yb0JsNGUvNXBORW1B?=
 =?utf-8?B?b3Yrb1BLTWR4RVZ2YTdINFZnQ2dDM3F6Ym9tbXJzUzRFU1ZWdnJLNVdqNlZQ?=
 =?utf-8?B?N1NYeXpsd2N0dS8yd01XMjNsb2lnZUhjcWxPRlNUaTMrNVNreUZDQzdDOG9y?=
 =?utf-8?B?dXJIV2t0T3Myc2RWaEtMcFphRFBzeTlIZ0JRVmlJUkFPay9vYU9GR0tGbVFU?=
 =?utf-8?B?d0pVMmVPSlVubVI0WHZDcnhyRXNsVTNMSDF6WVFtVzcwZnl5VVlkZGhJYy9B?=
 =?utf-8?B?WTBneHZjbmdsZzFhNWdzQmRIYWgvT05nOFNBWDE1elIyazhsQmZFNjZTaFhw?=
 =?utf-8?B?dG82NGViN1ZrWWJLWFFkOG9lRjA3dDNlT1V5c1hPL2o2bkIxenorSk1mTjY5?=
 =?utf-8?B?cHc9PQ==?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 76301df8-9415-4a71-e135-08da943aff27
X-MS-Exchange-CrossTenant-AuthSource: DM4PR11MB5373.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 11 Sep 2022 21:17:13.7101
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: cEtUsDVqkIZHemli3VY03qJdtjUYkl2ANR4l4s7jLZATOWb/ZIY5b/mF2hzNRCmXPqGda8IJfAsuiokC0sLS03lfDp9Juc1jUwyRyQfleWY=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR11MB6065
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-7.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_HI,
        SPF_HELO_NONE,SPF_NONE,T_SCC_BODY_TEXT_LINE autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

IDR is deprecated, and since XArray manages its own state with internal
locking, it simplifies the locking on DRM side.
Additionally, don't use the IRQ-safe variant, since operating on drm
minor is not done in IRQ context.

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
---
 drivers/gpu/drm/drm_drv.c | 51 ++++++++++++++-------------------------
 1 file changed, 18 insertions(+), 33 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 8214a0b1ab7f..61d24cdcd0f8 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -34,6 +34,7 @@
 #include <linux/pseudo_fs.h>
 #include <linux/slab.h>
 #include <linux/srcu.h>
+#include <linux/xarray.h>
 
 #include <drm/drm_cache.h>
 #include <drm/drm_client.h>
@@ -53,8 +54,7 @@ MODULE_AUTHOR("Gareth Hughes, Leif Delgass, José Fonseca, Jon Smirl");
 MODULE_DESCRIPTION("DRM shared core routines");
 MODULE_LICENSE("GPL and additional rights");
 
-static DEFINE_SPINLOCK(drm_minor_lock);
-static struct idr drm_minors_idr;
+static DEFINE_XARRAY_ALLOC(drm_minors_xa);
 
 /*
  * If the drm core fails to init for whatever reason,
@@ -98,21 +98,19 @@ static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
 static void drm_minor_alloc_release(struct drm_device *dev, void *data)
 {
 	struct drm_minor *minor = data;
-	unsigned long flags;
 
 	WARN_ON(dev != minor->dev);
 
 	put_device(minor->kdev);
 
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	idr_remove(&drm_minors_idr, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	xa_erase(&drm_minors_xa, minor->index);
 }
 
+#define DRM_MINOR_LIMIT(t) ({ typeof(t) _t = (t); XA_LIMIT(64 * _t, 64 * _t + 63); })
+
 static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 	int r;
 
 	minor = drmm_kzalloc(dev, sizeof(*minor), GFP_KERNEL);
@@ -122,21 +120,10 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 	minor->type = type;
 	minor->dev = dev;
 
-	idr_preload(GFP_KERNEL);
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	r = idr_alloc(&drm_minors_idr,
-		      NULL,
-		      64 * type,
-		      64 * (type + 1),
-		      GFP_NOWAIT);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
-	idr_preload_end();
-
+	r = xa_alloc(&drm_minors_xa, &minor->index, NULL, DRM_MINOR_LIMIT(type), GFP_KERNEL);
 	if (r < 0)
 		return r;
 
-	minor->index = r;
-
 	r = drmm_add_action_or_reset(dev, drm_minor_alloc_release, minor);
 	if (r)
 		return r;
@@ -152,7 +139,7 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 static int drm_minor_register(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
+	void *entry;
 	int ret;
 
 	DRM_DEBUG("\n");
@@ -172,9 +159,12 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
 		goto err_debugfs;
 
 	/* replace NULL with @minor so lookups will succeed from now on */
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	idr_replace(&drm_minors_idr, minor, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	entry = xa_cmpxchg(&drm_minors_xa, minor->index, NULL, &minor, GFP_KERNEL);
+	if (xa_is_err(entry)) {
+		ret = xa_err(entry);
+		goto err_debugfs;
+	}
+	WARN_ON(entry);
 
 	DRM_DEBUG("new minor registered %d\n", minor->index);
 	return 0;
@@ -187,16 +177,13 @@ static int drm_minor_register(struct drm_device *dev, unsigned int type)
 static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 
 	minor = *drm_minor_get_slot(dev, type);
 	if (!minor || !device_is_registered(minor->kdev))
 		return;
 
 	/* replace @minor with NULL so lookups will fail from now on */
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	idr_replace(&drm_minors_idr, NULL, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	xa_store(&drm_minors_xa, minor->index, NULL, GFP_KERNEL);
 
 	device_del(minor->kdev);
 	dev_set_drvdata(minor->kdev, NULL); /* safety belt */
@@ -215,13 +202,12 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 struct drm_minor *drm_minor_acquire(unsigned int minor_id)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	minor = idr_find(&drm_minors_idr, minor_id);
+	xa_lock(&drm_minors_xa);
+	minor = xa_load(&drm_minors_xa, minor_id);
 	if (minor)
 		drm_dev_get(minor->dev);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	xa_unlock(&drm_minors_xa);
 
 	if (!minor) {
 		return ERR_PTR(-ENODEV);
@@ -1037,7 +1023,7 @@ static void drm_core_exit(void)
 	unregister_chrdev(DRM_MAJOR, "drm");
 	debugfs_remove(drm_debugfs_root);
 	drm_sysfs_destroy();
-	idr_destroy(&drm_minors_idr);
+	WARN_ON(!xa_empty(&drm_minors_xa));
 	drm_connector_ida_destroy();
 }
 
@@ -1046,7 +1032,6 @@ static int __init drm_core_init(void)
 	int ret;
 
 	drm_connector_ida_init();
-	idr_init(&drm_minors_idr);
 	drm_memcpy_init_early();
 
 	ret = drm_sysfs_init();
-- 
2.37.3