[PATCH 01/34] drm: Convert drm_minors_idr to XArray

[Matthew Wilcox]

Divide all the indices by 64 to save memory.

Signed-off-by: Matthew Wilcox <willy at infradead.org>
---
 drivers/gpu/drm/drm_drv.c | 49 ++++++++++++++-------------------------
 1 file changed, 17 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 12e5e2be7890..17ed29f49060 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -64,8 +64,7 @@ MODULE_PARM_DESC(debug, "Enable debug output, where each bit enables a debug cat
 "\t\tBit 8 (0x100) will enable DP messages (displayport code)");
 module_param_named(debug, drm_debug, int, 0600);
 
-static DEFINE_SPINLOCK(drm_minor_lock);
-static struct idr drm_minors_idr;
+static DEFINE_XARRAY_FLAGS(drm_minors, XA_FLAGS_ALLOC | XA_FLAGS_LOCK_IRQ);
 
 /*
  * If the drm core fails to init for whatever reason,
@@ -109,7 +108,6 @@ static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
 static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *minor;
-	unsigned long flags;
 	int r;
 
 	minor = kzalloc(sizeof(*minor), GFP_KERNEL);
@@ -118,22 +116,12 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 
 	minor->type = type;
 	minor->dev = dev;
+	minor->index = 64 * type;
 
-	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_insert_irq(&drm_minors, minor->index / 64, NULL, GFP_KERNEL);
 	if (r < 0)
 		goto err_free;
 
-	minor->index = r;
-
 	minor->kdev = drm_sysfs_minor_alloc(minor);
 	if (IS_ERR(minor->kdev)) {
 		r = PTR_ERR(minor->kdev);
@@ -144,9 +132,7 @@ static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
 	return 0;
 
 err_index:
-	spin_lock_irqsave(&drm_minor_lock, flags);
-	idr_remove(&drm_minors_idr, minor->index);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	xa_erase_irq(&drm_minors, minor->index / 64);
 err_free:
 	kfree(minor);
 	return r;
@@ -164,9 +150,9 @@ static void drm_minor_free(struct drm_device *dev, unsigned int type)
 
 	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_lock_irqsave(&drm_minors, flags);
+	__xa_erase(&drm_minors, minor->index / 64);
+	xa_unlock_irqrestore(&drm_minors, flags);
 
 	kfree(minor);
 	*slot = NULL;
@@ -195,9 +181,9 @@ 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);
+	xa_lock_irqsave(&drm_minors, flags);
+	__xa_store(&drm_minors, minor->index / 64, minor, 0);
+	xa_unlock_irqrestore(&drm_minors, flags);
 
 	DRM_DEBUG("new minor registered %d\n", minor->index);
 	return 0;
@@ -217,9 +203,9 @@ static void drm_minor_unregister(struct drm_device *dev, unsigned int type)
 		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_lock_irqsave(&drm_minors, flags);
+	__xa_store(&drm_minors, minor->index / 64, NULL, 0);
+	xa_unlock_irqrestore(&drm_minors, flags);
 
 	device_del(minor->kdev);
 	dev_set_drvdata(minor->kdev, NULL); /* safety belt */
@@ -240,11 +226,11 @@ 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_irqsave(&drm_minors, flags);
+	minor = xa_load(&drm_minors, minor_id / 64);
 	if (minor)
 		drm_dev_get(minor->dev);
-	spin_unlock_irqrestore(&drm_minor_lock, flags);
+	xa_unlock_irqrestore(&drm_minors, flags);
 
 	if (!minor) {
 		return ERR_PTR(-ENODEV);
@@ -958,7 +944,7 @@ 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));
 	drm_connector_ida_destroy();
 }
 
@@ -967,7 +953,6 @@ static int __init drm_core_init(void)
 	int ret;
 
 	drm_connector_ida_init();
-	idr_init(&drm_minors_idr);
 
 	ret = drm_sysfs_init();
 	if (ret < 0) {
-- 
2.20.1