From: Matthew Wilcox <willy@infradead.org>
Date: Mon, 18 Feb 2019 21:29:20 +0000 (-0500)
Subject: pps: Convert pps_idr to XArray
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3bf1580b76a56c487cc3365d7d9c579fb1734d9d;p=users%2Fwilly%2Fxarray.git

pps: Convert pps_idr to XArray

The pps_idr_lock mutex is unnecessary thanks to the included xa_lock.

Signed-off-by: Matthew Wilcox <willy@infradead.org>
---

diff --git a/drivers/pps/kapi.c b/drivers/pps/kapi.c
index d9d566f70ed1..cd3172a69d2f 100644
--- a/drivers/pps/kapi.c
+++ b/drivers/pps/kapi.c
@@ -89,8 +89,9 @@ struct pps_device *pps_register_source(struct pps_source_info *info,
 		goto pps_register_source_exit;
 	}
 
-	/* These initializations must be done before calling idr_alloc()
-	 * in order to avoid reces into pps_event().
+	/*
+	 * These initializations must be done before calling
+	 * pps_register_cdev() in order to avoid races in pps_event().
 	 */
 	pps->params.api_version = PPS_API_VERS;
 	pps->params.mode = default_params;
diff --git a/drivers/pps/pps.c b/drivers/pps/pps.c
index 22a65ad4e46e..c7215782893d 100644
--- a/drivers/pps/pps.c
+++ b/drivers/pps/pps.c
@@ -12,12 +12,12 @@
 #include <linux/init.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
-#include <linux/idr.h>
 #include <linux/mutex.h>
 #include <linux/cdev.h>
 #include <linux/poll.h>
 #include <linux/pps_kernel.h>
 #include <linux/slab.h>
+#include <linux/xarray.h>
 
 #include "kc.h"
 
@@ -28,8 +28,7 @@
 static dev_t pps_devt;
 static struct class *pps_class;
 
-static DEFINE_MUTEX(pps_idr_lock);
-static DEFINE_IDR(pps_idr);
+static DEFINE_XARRAY_ALLOC(pps_devs);
 
 /*
  * Char device methods
@@ -336,9 +335,7 @@ static void pps_device_destruct(struct device *dev)
 
 	/* Now we can release the ID for re-use */
 	pr_debug("deallocating pps%d\n", pps->id);
-	mutex_lock(&pps_idr_lock);
-	idr_remove(&pps_idr, pps->id);
-	mutex_unlock(&pps_idr_lock);
+	xa_erase(&pps_devs, pps->id);
 
 	kfree(dev);
 	kfree(pps);
@@ -349,22 +346,19 @@ int pps_register_cdev(struct pps_device *pps)
 	int err;
 	dev_t devt;
 
-	mutex_lock(&pps_idr_lock);
 	/*
-	 * Get new ID for the new PPS source.  After idr_alloc() calling
-	 * the new source will be freely available into the kernel.
+	 * Get new ID for the new PPS source.  After this call
+	 * the new source will be freely available in the kernel.
 	 */
-	err = idr_alloc(&pps_idr, pps, 0, PPS_MAX_SOURCES, GFP_KERNEL);
+	err = xa_alloc(&pps_devs, &pps->id, pps,
+			XA_LIMIT(0, PPS_MAX_SOURCES - 1), GFP_KERNEL);
 	if (err < 0) {
-		if (err == -ENOSPC) {
+		if (err == -EBUSY) {
 			pr_err("%s: too many PPS sources in the system\n",
 			       pps->info.name);
-			err = -EBUSY;
 		}
-		goto out_unlock;
+		goto out;
 	}
-	pps->id = err;
-	mutex_unlock(&pps_idr_lock);
 
 	devt = MKDEV(MAJOR(pps_devt), pps->id);
 
@@ -375,7 +369,7 @@ int pps_register_cdev(struct pps_device *pps)
 	if (err) {
 		pr_err("%s: failed to add char device %d:%d\n",
 				pps->info.name, MAJOR(pps_devt), pps->id);
-		goto free_idr;
+		goto erase;
 	}
 	pps->dev = device_create(pps_class, pps->info.dev, devt, pps,
 							"pps%d", pps->id);
@@ -394,12 +388,9 @@ int pps_register_cdev(struct pps_device *pps)
 
 del_cdev:
 	cdev_del(&pps->cdev);
-
-free_idr:
-	mutex_lock(&pps_idr_lock);
-	idr_remove(&pps_idr, pps->id);
-out_unlock:
-	mutex_unlock(&pps_idr_lock);
+erase:
+	xa_erase(&pps_devs, pps->id);
+out:
 	return err;
 }
 
@@ -425,19 +416,17 @@ void pps_unregister_cdev(struct pps_device *pps)
  *
  * The cookie is automatically set to NULL in pps_unregister_source()
  * so that it will not be used again, even if the pps device cannot
- * be removed from the idr due to pending references holding the minor
+ * be removed from the array due to pending references holding the minor
  * number in use.
  */
 struct pps_device *pps_lookup_dev(void const *cookie)
 {
 	struct pps_device *pps;
-	unsigned id;
+	unsigned long id;
 
-	rcu_read_lock();
-	idr_for_each_entry(&pps_idr, pps, id)
+	xa_for_each(&pps_devs, id, pps)
 		if (cookie == pps->lookup_cookie)
 			break;
-	rcu_read_unlock();
 	return pps;
 }
 EXPORT_SYMBOL(pps_lookup_dev);