From 81f9aea3dbdec74149aaa1c58ceacfa9b63ed33f Mon Sep 17 00:00:00 2001
From: Matthew Wilcox <willy@infradead.org>
Date: Wed, 9 Jan 2019 08:34:37 -0500
Subject: [PATCH] target: Convert devices_idr to XArray

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
 drivers/target/target_core_device.c | 94 +++++++++++------------------
 1 file changed, 34 insertions(+), 60 deletions(-)

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 04bf2acd3800..1c86613a5cc4 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -36,9 +36,7 @@
 #include "target_core_pr.h"
 #include "target_core_ua.h"
 
-static DEFINE_MUTEX(device_mutex);
-static LIST_HEAD(device_list);
-static DEFINE_IDR(devices_idr);
+static DEFINE_XARRAY_ALLOC(device_list);
 
 static struct se_hba *lun0_hba;
 /* not static, needed by tpg.c */
@@ -853,42 +851,6 @@ sector_t target_to_linux_sector(struct se_device *dev, sector_t lb)
 }
 EXPORT_SYMBOL(target_to_linux_sector);
 
-struct devices_idr_iter {
-	struct config_item *prev_item;
-	int (*fn)(struct se_device *dev, void *data);
-	void *data;
-};
-
-static int target_devices_idr_iter(int id, void *p, void *data)
-	 __must_hold(&device_mutex)
-{
-	struct devices_idr_iter *iter = data;
-	struct se_device *dev = p;
-	int ret;
-
-	config_item_put(iter->prev_item);
-	iter->prev_item = NULL;
-
-	/*
-	 * We add the device early to the idr, so it can be used
-	 * by backend modules during configuration. We do not want
-	 * to allow other callers to access partially setup devices,
-	 * so we skip them here.
-	 */
-	if (!target_dev_configured(dev))
-		return 0;
-
-	iter->prev_item = config_item_get_unless_zero(&dev->dev_group.cg_item);
-	if (!iter->prev_item)
-		return 0;
-	mutex_unlock(&device_mutex);
-
-	ret = iter->fn(dev, iter->data);
-
-	mutex_lock(&device_mutex);
-	return ret;
-}
-
 /**
  * target_for_each_device - iterate over configured devices
  * @fn: iterator function
@@ -900,20 +862,41 @@ static int target_devices_idr_iter(int id, void *p, void *data)
 int target_for_each_device(int (*fn)(struct se_device *dev, void *data),
 			   void *data)
 {
-	struct devices_idr_iter iter = { .fn = fn, .data = data };
-	int ret;
+	unsigned long i;
+	struct se_device *dev;
+	int ret = 0;
+
+	xa_for_each(&device_list, i, dev) {
+		struct config_item *item;
+
+		/*
+		 * We add the device early to the list, so it can be used
+		 * by backend modules during configuration. We do not want
+		 * to allow other callers to access partially setup devices,
+		 * so we skip them here.
+		 */
+		if (!target_dev_configured(dev))
+			continue;
+
+		item = config_item_get_unless_zero(&dev->dev_group.cg_item);
+		if (!item)
+			continue;
+
+		ret = fn(dev, data);
+
+		config_item_put(item);
+		if (ret)
+			break;
+	}
 
-	mutex_lock(&device_mutex);
-	ret = idr_for_each(&devices_idr, target_devices_idr_iter, &iter);
-	mutex_unlock(&device_mutex);
-	config_item_put(iter.prev_item);
 	return ret;
 }
 
 int target_configure_device(struct se_device *dev)
 {
+	static u32 next;
 	struct se_hba *hba = dev->se_hba;
-	int ret, id;
+	int ret;
 
 	if (target_dev_configured(dev)) {
 		pr_err("se_dev->se_dev_ptr already set for storage"
@@ -924,19 +907,15 @@ int target_configure_device(struct se_device *dev)
 	/*
 	 * Add early so modules like tcmu can use during its
 	 * configuration.
-	 */
-	mutex_lock(&device_mutex);
-	/*
 	 * Use cyclic to try and avoid collisions with devices
 	 * that were recently removed.
 	 */
-	id = idr_alloc_cyclic(&devices_idr, dev, 0, INT_MAX, GFP_KERNEL);
-	mutex_unlock(&device_mutex);
-	if (id < 0) {
+	ret = xa_alloc_cyclic(&device_list, &dev->dev_index, dev, xa_limit_32b,
+			&next, GFP_KERNEL);
+	if (ret < 0) {
 		ret = -ENOMEM;
 		goto out;
 	}
-	dev->dev_index = id;
 
 	ret = dev->transport->configure_device(dev);
 	if (ret)
@@ -979,9 +958,7 @@ int target_configure_device(struct se_device *dev)
 out_destroy_device:
 	dev->transport->destroy_device(dev);
 out_free_index:
-	mutex_lock(&device_mutex);
-	idr_remove(&devices_idr, dev->dev_index);
-	mutex_unlock(&device_mutex);
+	xa_erase(&device_list, dev->dev_index);
 out:
 	se_release_vpd_for_dev(dev);
 	return ret;
@@ -995,10 +972,7 @@ void target_free_device(struct se_device *dev)
 
 	if (target_dev_configured(dev)) {
 		dev->transport->destroy_device(dev);
-
-		mutex_lock(&device_mutex);
-		idr_remove(&devices_idr, dev->dev_index);
-		mutex_unlock(&device_mutex);
+		xa_erase(&device_list, dev->dev_index);
 
 		spin_lock(&hba->device_lock);
 		hba->dev_count--;
-- 
2.50.1