Cluster Project branch, RHEL5, updated. cmirror_1_1_15-120-g656a865

[bmarzins@sourceware.org]

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- Log -----------------------------------------------------------------
commit 656a865047bb5f6f9461a7cde7a78d45602fc1fa
Author: Benjamin Marzinski <bmarzins@redhat.com>
Date:   Thu Jun 19 13:14:43 2008 -0500

    gnbd-kernel: Fix receiver race
    
    It is possible to have the gnbd receiver process finish and end a request before
    the sending process has finished using the request structure.  This can cause a
    kernel panic.
    
    This fix adds a waitqueue (tx_wait) and a pointer to the request currently
    being send (current_request) to the gnbd device structure.  current_request is
    set before any request is sent to the server. When the send is complete, it is
    cleared and the wait_queue is woken.  A new function, wait_for_send() is called
    whenever it is possible for a call to gnbd_end_request() to interleave with a
    send. It waits on the waitqueue if the request about to be ended is currently
    being sent.

-----------------------------------------------------------------------

Summary of changes:
 gnbd-kernel/src/gnbd.c |   47 +++++++++++++++++++++++++++++++++++++++++++----
 gnbd-kernel/src/gnbd.h |    2 ++
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/gnbd-kernel/src/gnbd.c b/gnbd-kernel/src/gnbd.c
index d637141..41b0c2b 100644
--- a/gnbd-kernel/src/gnbd.c
+++ b/gnbd-kernel/src/gnbd.c
@@ -267,6 +267,26 @@ static const char *gnbdcmd_to_ascii(int cmd)
 }
 #endif /* NDEBUG */
 
+
+static int wait_for_send(struct request *req, struct gnbd_device *dev)
+{
+	DECLARE_WAITQUEUE(wait, current);
+
+	add_wait_queue(&dev->tx_wait, &wait);
+	while(dev->current_request == req) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		if (signal_pending(current)) {
+			printk(KERN_WARNING "gnbd (pid %d: %s) wait interrupted by signal\n",
+				current->pid, current->comm);
+			return -EINTR;
+		}
+		schedule();
+	}
+	set_current_state(TASK_RUNNING);
+	remove_wait_queue(&dev->tx_wait, &wait);
+	return 0;
+}
+
 static void gnbd_end_request(struct request *req)
 {
 	int uptodate = (req->errors == 0) ? 1 : 0;
@@ -396,13 +416,14 @@ int __gnbd_send_req(struct gnbd_device *dev, struct socket *sock,
 			gnbdcmd_to_ascii(gnbd_cmd(req)),
 			(unsigned long long)req->sector << 9,
 			req->nr_sectors << 9);
+	dev->current_request = req;
 	result = sock_xmit(sock, 1, &request, sizeof(request),
 			(gnbd_cmd(req) == GNBD_CMD_WRITE)? MSG_MORE: 0,
 			can_signal);
 	if (result < 0) {
 		printk(KERN_ERR "%s: Send control failed (result %d)\n",
 				dev->disk->disk_name, result);
-		goto error_out;
+		goto send_error_out;
 	}
 
 	if (gnbd_cmd(req) == GNBD_CMD_WRITE) {
@@ -426,14 +447,19 @@ int __gnbd_send_req(struct gnbd_device *dev, struct socket *sock,
 					printk(KERN_ERR "%s: Send data failed (result %d)\n",
 							dev->disk->disk_name,
 							result);
-					goto error_out;
+					goto send_error_out;
 				}
 			}
 		}
 	}
+	dev->current_request = NULL;
+	wake_up(&dev->tx_wait);
 	up(&dev->tx_lock);
 	return 0;
 
+send_error_out:
+	dev->current_request = NULL;
+	wake_up(&dev->tx_wait);
 error_out:
 	up(&dev->tx_lock);
 	return result;
@@ -530,6 +556,9 @@ int gnbd_do_it(struct gnbd_device *dev)
 				return result;
 		}
 remove_req:
+		result = wait_for_send(req, dev);
+		if (result != 0)
+			return result;
 		spin_lock(&dev->queue_lock);
 		list_del_init(&req->queuelist);
 		dev->last_received = jiffies;
@@ -542,8 +571,9 @@ remove_req:
 	return result;
 }
 
-void gnbd_clear_que(struct gnbd_device *dev)
+int gnbd_clear_que(struct gnbd_device *dev)
 {
+	int err;
 	struct request *req;
 
 	BUG_ON(dev->magic != GNBD_MAGIC);
@@ -552,6 +582,9 @@ void gnbd_clear_que(struct gnbd_device *dev)
 		req = NULL;
 		if (!list_empty(&dev->queue_head)) {
 			req = list_entry(dev->queue_head.next, struct request, queuelist);
+			err = wait_for_send(req, dev);
+			if (err)
+				return err;
 			list_del_init(&req->queuelist);
 		}
 		if (req && req != &ping_req) {
@@ -559,6 +592,8 @@ void gnbd_clear_que(struct gnbd_device *dev)
 			gnbd_end_request(req);
 		}
 	} while (req);
+
+	return 0;
 }
 
 /*
@@ -712,7 +747,9 @@ static int gnbd_ctl_ioctl(struct inode *inode, struct file *file,
 		if (down_interruptible(&dev->do_it_lock))
 			return -EBUSY;
 		dev->receiver_pid = -1;
-		gnbd_clear_que(dev);
+		error = gnbd_clear_que(dev);
+		if (error)
+			return error;
 		bdev = dev->bdev;
 		if (bdev) {
 			blk_run_queue(dev->disk->queue);
@@ -982,6 +1019,8 @@ static int __init gnbd_init(void)
 		INIT_LIST_HEAD(&gnbd_dev[i].queue_head);
 		init_MUTEX(&gnbd_dev[i].tx_lock);
 		init_MUTEX(&gnbd_dev[i].do_it_lock);
+		init_waitqueue_head(&gnbd_dev[i].tx_wait);
+		gnbd_dev[i].current_request = NULL;
 		gnbd_dev[i].class_dev.class = &gnbd_class;
 		sprintf(gnbd_dev[i].class_dev.class_id, "gnbd%d", i);
 		err = class_device_register(&gnbd_dev[i].class_dev);
diff --git a/gnbd-kernel/src/gnbd.h b/gnbd-kernel/src/gnbd.h
index b88ad26..50da10b 100644
--- a/gnbd-kernel/src/gnbd.h
+++ b/gnbd-kernel/src/gnbd.h
@@ -56,6 +56,8 @@ struct gnbd_device {
 	char name[32];
 	unsigned long last_received;
 	struct block_device *bdev;
+	struct request *current_request;
+	wait_queue_head_t tx_wait;
 };
 
 #endif /* __KERNEL__ */


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