linux-kernel - [PATCH] firewire: fail open() quickly if the node doesn't exist anymore

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Date:	Sun, 27 Jan 2008 18:21:56 +0100 (CET)
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	linux1394-devel@...ts.sourceforge.net
cc:	Jarod Wilson <jwilson@...hat.com>,
	Kristian Høgsberg <krh@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] firewire: fail open() quickly if the node doesn't exist
 anymore

Scenario:  Process A keeps the character device file of node N open.
N is being unplugged.  File /dev/fwN won't be destroyed as long as A
doesn't close it.  Now, process B opens /dev/fwN as well.  Previously
it would succeed but be unable to do any IO on it of course.  With this
patch, process B's open() will fail immediately with -ENODEV.

Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
---
 drivers/firewire/fw-device.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Index: linux/drivers/firewire/fw-device.c
===================================================================
--- linux.orig/drivers/firewire/fw-device.c
+++ linux/drivers/firewire/fw-device.c
@@ -616,8 +616,12 @@ struct fw_device *fw_device_from_devt(de
 
 	down_read(&idr_rwsem);
 	device = idr_find(&fw_device_idr, MINOR(devt));
-	if (device)
-		fw_device_get(device);
+	if (device) {
+		if (fw_device_is_shutdown(device))
+			device = NULL;
+		else
+			fw_device_get(device);
+	}
 	up_read(&idr_rwsem);
 
 	return device;

-- 
Stefan Richter
-=====-==--- ---= ==-==
http://arcgraph.de/sr/

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