Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Received-SPF: Pass (protection.outlook.com: domain of nokia.com designates
 131.228.2.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=131.228.2.17; helo=fihe3nok0735.emea.nsn-net.net;
From:   Alexander A Sverdlin <alexander.sverdlin@nokia.com>
To:     linux-mtd@lists.infradead.org
Cc:     Alexander Sverdlin <alexander.sverdlin@nokia.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] mtd: char: Get rid of Big MTD Lock
Date:   Wed, 17 Feb 2021 22:18:45 +0100
Message-Id: <20210217211845.43364-2-alexander.sverdlin@nokia.com>
In-Reply-To: <20210217211845.43364-1-alexander.sverdlin@nokia.com>
References: <20210217211845.43364-1-alexander.sverdlin@nokia.com>
MIME-Version: 1.0
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Feb 2021 21:18:53.1978
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 2e665b0a-8223-4e2d-1ad2-08d8d389a0b3
X-MS-Exchange-CrossTenant-Id: 5d471751-9675-428d-917b-70f44f9630b0
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=5d471751-9675-428d-917b-70f44f9630b0;Ip=[131.228.2.17];Helo=[fihe3nok0735.emea.nsn-net.net]
X-MS-Exchange-CrossTenant-AuthSource: VE1EUR03FT011.eop-EUR03.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR07MB7430
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

From: Alexander Sverdlin <alexander.sverdlin@nokia.com>

Get rid of central chrdev MTD lock, which prevents simultaneous operations
on completely independent physical MTD chips. Replace it with newly
introduced per-master mutex.

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
---
 drivers/mtd/mtdchar.c   | 14 ++++++++------
 drivers/mtd/mtdcore.c   |  1 +
 include/linux/mtd/mtd.h |  1 +
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index f31390d..57c4a2f 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -27,8 +27,6 @@
 
 #include "mtdcore.h"
 
-static DEFINE_MUTEX(mtd_mutex);
-
 /*
  * Data structure to hold the pointer to the mtd device as well
  * as mode information of various use cases.
@@ -1020,11 +1018,14 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
 
 static long mtdchar_unlocked_ioctl(struct file *file, u_int cmd, u_long arg)
 {
+	struct mtd_file_info *mfi = file->private_data;
+	struct mtd_info *mtd = mfi->mtd;
+	struct mtd_info *master = mtd_get_master(mtd);
 	int ret;
 
-	mutex_lock(&mtd_mutex);
+	mutex_lock(&master->master.chrdev_lock);
 	ret = mtdchar_ioctl(file, cmd, arg);
-	mutex_unlock(&mtd_mutex);
+	mutex_unlock(&master->master.chrdev_lock);
 
 	return ret;
 }
@@ -1045,10 +1046,11 @@ static long mtdchar_compat_ioctl(struct file *file, unsigned int cmd,
 {
 	struct mtd_file_info *mfi = file->private_data;
 	struct mtd_info *mtd = mfi->mtd;
+	struct mtd_info *master = mtd_get_master(mtd);
 	void __user *argp = compat_ptr(arg);
 	int ret = 0;
 
-	mutex_lock(&mtd_mutex);
+	mutex_lock(&master->master.chrdev_lock);
 
 	switch (cmd) {
 	case MEMWRITEOOB32:
@@ -1111,7 +1113,7 @@ static long mtdchar_compat_ioctl(struct file *file, unsigned int cmd,
 		ret = mtdchar_ioctl(file, cmd, (unsigned long)argp);
 	}
 
-	mutex_unlock(&mtd_mutex);
+	mutex_unlock(&master->master.chrdev_lock);
 
 	return ret;
 }
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 2d6423d..0b09597 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -773,6 +773,7 @@ static void mtd_set_dev_defaults(struct mtd_info *mtd)
 
 	INIT_LIST_HEAD(&mtd->partitions);
 	mutex_init(&mtd->master.partitions_lock);
+	mutex_init(&mtd->master.chrdev_lock);
 }
 
 /**
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 157357e..ceabc2c 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -229,6 +229,7 @@ struct mtd_part {
  */
 struct mtd_master {
 	struct mutex partitions_lock;
+	struct mutex chrdev_lock;
 	unsigned int suspended : 1;
 };
 
-- 
2.10.2