From 8e0578365057642ce232c0d36c088f838e6c6aba Mon Sep 17 00:00:00 2001
From: Alasdair G Kergon <agk@redhat.com>
Date: Thu, 2 Apr 2009 19:55:28 +0100
Subject: [PATCH] --- yaml --- r: 140159 b: refs/heads/master c:
 570b9d968bf9b16974252ef7cbce73fa6dac34f3 h: refs/heads/master i:   140157:
 2c35c9dd62ecef01cd04bd14e84772cb2ab9c8bf   140155:
 ed398d7de115bf31a42e6dc3dd0710837f04bd45   140151:
 5548fac611293843b834c21bf5841de47710a682   140143:
 fef02563e4996efe5ed7e3e0e4861270312f70bc   140127:
 b5edb1e09a4fa20c334cc7bd30c848862631f58c   140095:
 2447ac733b009ab374864d9bc12c69159b193c4f   140031:
 c7c9efaf6cf9201b35104eeafb3c21b4af3a27b6 v: v3

---
 [refs]                      |  2 +-
 trunk/drivers/md/dm-table.c | 26 ++++++++++++++------------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/[refs] b/[refs]
index 9d0c297c7551..5eba613857da 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: aea9058801c0acfa2831af1714da412dfb0018c2
+refs/heads/master: 570b9d968bf9b16974252ef7cbce73fa6dac34f3
diff --git a/trunk/drivers/md/dm-table.c b/trunk/drivers/md/dm-table.c
index 2fd66c30f7f8..e8361b191b9b 100644
--- a/trunk/drivers/md/dm-table.c
+++ b/trunk/drivers/md/dm-table.c
@@ -399,28 +399,30 @@ static int check_device_area(struct dm_dev_internal *dd, sector_t start,
 }
 
 /*
- * This upgrades the mode on an already open dm_dev.  Being
+ * This upgrades the mode on an already open dm_dev, being
  * careful to leave things as they were if we fail to reopen the
- * device.
+ * device and not to touch the existing bdev field in case
+ * it is accessed concurrently inside dm_table_any_congested().
  */
 static int upgrade_mode(struct dm_dev_internal *dd, fmode_t new_mode,
 			struct mapped_device *md)
 {
 	int r;
-	struct dm_dev_internal dd_copy;
-	dev_t dev = dd->dm_dev.bdev->bd_dev;
+	struct dm_dev_internal dd_new, dd_old;
 
-	dd_copy = *dd;
+	dd_new = dd_old = *dd;
+
+	dd_new.dm_dev.mode |= new_mode;
+	dd_new.dm_dev.bdev = NULL;
+
+	r = open_dev(&dd_new, dd->dm_dev.bdev->bd_dev, md);
+	if (r)
+		return r;
 
 	dd->dm_dev.mode |= new_mode;
-	dd->dm_dev.bdev = NULL;
-	r = open_dev(dd, dev, md);
-	if (!r)
-		close_dev(&dd_copy, md);
-	else
-		*dd = dd_copy;
+	close_dev(&dd_old, md);
 
-	return r;
+	return 0;
 }
 
 /*