[lkcd-devel] [PATCH] reset default polling value on device setup error

[Greg E. <edw...@sg...>]

While tracking down some other issues relating to passing a bogus dump
device to /sys/dump/dumpdev, one of the unintended results of passing in
a bad device is the default polling value is switched.  For systems that
need to use polling, this means you would need to

	echo 1 > /sys/dump/polling

before it would set up a [correct] device.  This includes running
configdump.  Patch below saves off the default value and resets it at
the end if the call to dump_block_intr_open() also failed.

Greg

---
 drivers/dump/dump_blockdev.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Index: linux-2.6.16/drivers/dump/dump_blockdev.c
===================================================================
--- linux-2.6.16.orig/drivers/dump/dump_blockdev.c	2006-05-12 13:26:49.698440429 -0500
+++ linux-2.6.16/drivers/dump/dump_blockdev.c	2006-05-12 13:44:59.522854094 -0500
@@ -468,6 +468,8 @@ static int
 dump_block_open(struct dump_dev *dev, const char *arg)
 {
 	unsigned long devid;
+	int poll = dump_config.polling;
+	int ret;
 
 	if ((sscanf(arg, "%lx", &devid)) != 1)
 		return -EINVAL;
@@ -475,21 +477,27 @@ dump_block_open(struct dump_dev *dev, co
 	if (devid < 0)
 		return -EINVAL;
 
-	if (dump_config.polling){
+	if (poll) {
 		polling_mode = 1;
 		if (!dump_block_poll_open(dev, devid)) {
 			return 0;
 		} else {
 			/*
-			 * If polling I/O isn't supported by this
-			 * device, fall back to interrupt-driven mode.
+			 * Either polling I/O isn't supported by this
+			 * device, or we were fed a bogus device.  Let's
+			 * try to fall back to interrupt-driven mode.
 			 */
 			dump_config.polling = 0;
 		}
 	}
 
 	polling_mode = 0;
-	return dump_block_intr_open(dev, devid);
+	ret = dump_block_intr_open(dev, devid);
+	if (ret && (dump_config.polling != poll)) {
+		/* reset default polling value */
+		dump_config.polling = poll;
+	}
+	return ret;
 }
 
 /*