                                                                                                                                                                                                                                                               
Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: [PATCH v2 2/2] elevator: acquire q->sysfs_lock in elevator_change()
To:	linux-kernel@vger.kernel.org
From:	Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Cc:	axboe@kernel.dk, tj@kernel.org, seiji.aguchi@hds.com,
	vgoyal@redhat.com, majianpeng@gmail.com
Date:	Fri, 30 Aug 2013 18:47:16 -0400
Message-ID: <20130830224716.21812.99333.stgit@hds.com>
In-Reply-To: <20130830224707.21812.63516.stgit@hds.com>
References: <20130830224707.21812.63516.stgit@hds.com>
User-Agent: StGit/0.16
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Sender:	linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add locking of q->sysfs_lock into elevator_change() (an exported function)
to ensure it is held to protect q->elevator from elevator_init(), even if
elevator_change() is called from non-sysfs paths.
sysfs path (elv_iosched_store) uses __elevator_change(), non-locking
version, as the lock is already taken by elv_iosched_store().

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
---
 block/elevator.c |   16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 02d4390..6d765f7 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -965,7 +965,7 @@ fail_init:
 /*
  * Switch this queue to the given IO scheduler.
  */
-int elevator_change(struct request_queue *q, const char *name)
+static int __elevator_change(struct request_queue *q, const char *name)
 {
 	char elevator_name[ELV_NAME_MAX];
 	struct elevator_type *e;
@@ -987,6 +987,18 @@ int elevator_change(struct request_queue *q, const char *name)
 
 	return elevator_switch(q, e);
 }
+
+int elevator_change(struct request_queue *q, const char *name)
+{
+	int ret;
+
+	/* Protect q->elevator from elevator_init() */
+	mutex_lock(&q->sysfs_lock);
+	ret = __elevator_change(q, name);
+	mutex_unlock(&q->sysfs_lock);
+
+	return ret;
+}
 EXPORT_SYMBOL(elevator_change);
 
 ssize_t elv_iosched_store(struct request_queue *q, const char *name,
@@ -997,7 +1009,7 @@ ssize_t elv_iosched_store(struct request_queue *q, const char *name,
 	if (!q->elevator)
 		return count;
 
-	ret = elevator_change(q, name);
+	ret = __elevator_change(q, name);
 	if (!ret)
 		return count;
 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/