From 3ea0a8b182b2ed64368c48f30be58f187a2986ad Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@suse.de>
Date: Thu, 15 Apr 2010 10:13:47 +1000
Subject: [PATCH] --- yaml --- r: 197470 b: refs/heads/master c:
 b6eb127d274385d81ce8dd45c98190f097bce1b4 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/drivers/md/md.c | 41 +++++++++++++++++++++++++++++++----------
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/[refs] b/[refs]
index 8f2ca3ffa48e..dc3d2c79e318 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: ef2f80ff7325b2c1888ff02ead28957b5840bf51
+refs/heads/master: b6eb127d274385d81ce8dd45c98190f097bce1b4
diff --git a/trunk/drivers/md/md.c b/trunk/drivers/md/md.c
index 08f665178c3b..edf777f6fe56 100644
--- a/trunk/drivers/md/md.c
+++ b/trunk/drivers/md/md.c
@@ -507,9 +507,32 @@ static inline int mddev_trylock(mddev_t * mddev)
 	return mutex_trylock(&mddev->reconfig_mutex);
 }
 
+static struct attribute_group md_redundancy_group;
+
 static inline void mddev_unlock(mddev_t * mddev)
 {
-	mutex_unlock(&mddev->reconfig_mutex);
+	if (mddev->pers == NULL && mddev->private) {
+		/* These cannot be removed under reconfig_mutex as
+		 * an access to the files will try to take reconfig_mutex
+		 * while holding the file unremovable, which leads to
+		 * a deadlock.
+		 * So hold open_mutex instead - we are allowed to take
+		 * it while holding reconfig_mutex, and md_run can
+		 * use it to wait for the remove to complete.
+		 */
+		mutex_lock(&mddev->open_mutex);
+		mutex_unlock(&mddev->reconfig_mutex);
+
+		sysfs_remove_group(&mddev->kobj, &md_redundancy_group);
+		if (mddev->private != (void*)1)
+			sysfs_remove_group(&mddev->kobj, mddev->private);
+		if (mddev->sysfs_action)
+			sysfs_put(mddev->sysfs_action);
+		mddev->sysfs_action = NULL;
+		mddev->private = NULL;
+		mutex_unlock(&mddev->open_mutex);
+	} else
+		mutex_unlock(&mddev->reconfig_mutex);
 
 	md_wakeup_thread(mddev->thread);
 }
@@ -4075,15 +4098,6 @@ static void mddev_delayed_delete(struct work_struct *ws)
 {
 	mddev_t *mddev = container_of(ws, mddev_t, del_work);
 
-	if (mddev->private) {
-		sysfs_remove_group(&mddev->kobj, &md_redundancy_group);
-		if (mddev->private != (void*)1)
-			sysfs_remove_group(&mddev->kobj, mddev->private);
-		if (mddev->sysfs_action)
-			sysfs_put(mddev->sysfs_action);
-		mddev->sysfs_action = NULL;
-		mddev->private = NULL;
-	}
 	sysfs_remove_group(&mddev->kobj, &md_bitmap_group);
 	kobject_del(&mddev->kobj);
 	kobject_put(&mddev->kobj);
@@ -4241,6 +4255,13 @@ static int do_md_run(mddev_t * mddev)
 	if (mddev->pers)
 		return -EBUSY;
 
+	/* These two calls synchronise us with the
+	 * sysfs_remove_group calls in mddev_unlock,
+	 * so they must have completed.
+	 */
+	mutex_lock(&mddev->open_mutex);
+	mutex_unlock(&mddev->open_mutex);
+
 	/*
 	 * Analyze all RAID superblock(s)
 	 */