From a231e6283e1c79a33d6f3bdf786832f10e355d0c Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Fri, 17 Jul 2020 18:19:58 +0200
Subject: [KERNEL] Trying to get locking under control

Current code doesn't pay much attention to properly locking when
accessing structures that are being used in multiple workers/threads.
Try to fix this, slowly.
---
 src/kernel/core.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

(limited to 'src/kernel/core.c')

diff --git a/src/kernel/core.c b/src/kernel/core.c
index 35ea1ef..8da2b39 100644
--- a/src/kernel/core.c
+++ b/src/kernel/core.c
@@ -124,6 +124,7 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 	switch (cmd) {
 	case IOCTL_OPEN:
 		debug_dev(dev, "ioctl open");
+		mutex_lock(&dev->device_lock);
 		if (dev->imgname != NULL) {
 			result = -EBUSY;
 		} else if (imgname == NULL) {
@@ -131,7 +132,6 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 		} else if (msg == NULL) {
 			result = -EINVAL;
 		} else {
-			mutex_lock(&dev->device_lock);
 			if (sizeof(msg->host) != sizeof(dnbd3_host_t)) {
 				warn_dev(dev, "odd size bug#1 triggered in ioctl");
 			}
@@ -154,7 +154,6 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 			} else {
 				dev->number_connections = msg->number_connections;
 			}
-			mutex_unlock(&dev->device_lock);
 
 			result = dnbd3_net_connect(dev);
 			if (result) {
@@ -165,10 +164,12 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 			}
 			imgname = NULL;
 		}
+		mutex_unlock(&dev->device_lock);
 		break;
 
 	case IOCTL_CLOSE:
 		debug_dev(dev, "ioctl close");
+		mutex_lock(&dev->device_lock);
 		result = dnbd3_net_disconnect(dev);
 		set_capacity(dev->disk, 0);
 		if (dev->imgname) {
@@ -177,6 +178,7 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 		}
 		dev->rid = 0;
 		dev->reported_size = 0;
+		mutex_unlock(&dev->device_lock);
 		break;
 
 	case IOCTL_SWITCH:
@@ -187,6 +189,7 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 	case IOCTL_ADD_SRV:
 	case IOCTL_REM_SRV:
 		debug_dev(dev, "ioctl add/rem srv");
+		mutex_lock(&dev->device_lock);
 		if (dev->imgname == NULL) {
 			result = -ENOENT;
 		} else if (dev->new_servers_num >= NUMBER_SERVERS) {
@@ -194,16 +197,15 @@ static int dnbd3_ioctl(struct block_device *bdev, fmode_t mode,
 		} else if (msg == NULL) {
 			result = -EINVAL;
 		} else {
-			mutex_lock(&dev->device_lock);
 			memcpy(&dev->new_servers[dev->new_servers_num].host,
 					&msg->host, sizeof(msg->host));
 			/* 0 = ADD, 1 = REM */
 			dev->new_servers[dev->new_servers_num].failures =
 					(cmd == IOCTL_ADD_SRV ? 0 : 1);
 			dev->new_servers_num++;
-			mutex_unlock(&dev->device_lock);
 			result = 0;
 		}
+		mutex_unlock(&dev->device_lock);
 		break;
 
 	case BLKFLSBUF:
@@ -417,7 +419,7 @@ static void dnbd3_dev_remove(struct dnbd3_device *dev)
 	struct gendisk *disk = dev->disk;
 	struct request_queue *q;
 
-	if (dev->connected) {
+	if (dev->socks) {
 		dnbd3_net_disconnect(dev);
 	}
 
-- 
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