[PATCH -rt 2/2] Make sure d_kill sets d_parent to null

[John Stultz <johnstul@us.ibm.com>]

Patch against currrent 2.6.33-rt tree.

This patch is an alternative fix to the select_parent panic that was
suggested by Nick Piggin.

It resolves the issue by making sure d_parent is set to null so that
the dentry ascending code in select_parent will restart if the child
or next dentry was dkilled while the locks were released.

Credit and thanks to Nick for finding the solution.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Nick Piggin <npiggin@suse.de>
CC: Peter Zijlstra <peterz@infradead.org>
CC: John Kacur <jkacur@redhat.com>
---
 fs/dcache.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index da90157..c9d21ae 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -225,13 +225,15 @@ static struct dentry *d_kill(struct dentry *dentry)
 {
 	struct dentry *parent;
 
-	list_del(&dentry->d_u.d_child);
-	if (dentry->d_parent && dentry != dentry->d_parent)
-		spin_unlock(&dentry->d_parent->d_lock);
 	if (IS_ROOT(dentry))
 		parent = NULL;
 	else
 		parent = dentry->d_parent;
+
+	dentry->d_parent = NULL;
+	list_del(&dentry->d_u.d_child);
+	if (parent)
+		spin_unlock(&parent->d_lock);
 	/*drops the locks, at that point nobody can reach this dentry */
 	dentry_iput(dentry);
 	d_free(dentry);
-- 
1.6.0.4