linux-kernel - [PATCH v2] block/rnbd: Remove a useless mutex

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Date:   Mon,  7 Feb 2022 21:48:19 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     "Md. Haris Iqbal" <haris.iqbal@...os.com>,
        Jack Wang <jinpu.wang@...os.com>, Jens Axboe <axboe@...nel.dk>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        linux-block@...r.kernel.org
Subject: [PATCH v2] block/rnbd: Remove a useless mutex

According to lib/idr.c,
   The IDA handles its own locking.  It is safe to call any of the IDA
   functions without synchronisation in your code.

so the 'ida_lock' mutex can just be removed.
It is here only to protect some ida_simple_get()/ida_simple_remove() calls.

While at it, switch to ida_alloc_XXX()/ida_free() instead to
ida_simple_get()/ida_simple_remove().
The latter is deprecated and more verbose.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 drivers/block/rnbd/rnbd-clt.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/block/rnbd/rnbd-clt.c b/drivers/block/rnbd/rnbd-clt.c
index 9a880d559ab8..1f63f308eb39 100644
--- a/drivers/block/rnbd/rnbd-clt.c
+++ b/drivers/block/rnbd/rnbd-clt.c
@@ -23,7 +23,6 @@ MODULE_LICENSE("GPL");
 
 static int rnbd_client_major;
 static DEFINE_IDA(index_ida);
-static DEFINE_MUTEX(ida_lock);
 static DEFINE_MUTEX(sess_lock);
 static LIST_HEAD(sess_list);
 
@@ -55,9 +54,7 @@ static void rnbd_clt_put_dev(struct rnbd_clt_dev *dev)
 	if (!refcount_dec_and_test(&dev->refcount))
 		return;
 
-	mutex_lock(&ida_lock);
-	ida_simple_remove(&index_ida, dev->clt_device_id);
-	mutex_unlock(&ida_lock);
+	ida_free(&index_ida, dev->clt_device_id);
 	kfree(dev->hw_queues);
 	kfree(dev->pathname);
 	rnbd_clt_put_sess(dev->sess);
@@ -1460,10 +1457,8 @@ static struct rnbd_clt_dev *init_dev(struct rnbd_clt_session *sess,
 		goto out_alloc;
 	}
 
-	mutex_lock(&ida_lock);
-	ret = ida_simple_get(&index_ida, 0, 1 << (MINORBITS - RNBD_PART_BITS),
-			     GFP_KERNEL);
-	mutex_unlock(&ida_lock);
+	ret = ida_alloc_max(&index_ida, 1 << (MINORBITS - RNBD_PART_BITS),
+			    GFP_KERNEL);
 	if (ret < 0) {
 		pr_err("Failed to initialize device '%s' from session %s, allocating idr failed, err: %d\n",
 		       pathname, sess->sessname, ret);
-- 
2.32.0