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

From: John Stultz
Date: Wed Jun 30 2010 - 15:12:43 EST

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@xxxxxxxxxx>
CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CC: Nick Piggin <npiggin@xxxxxxx>
CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CC: John Kacur <jkacur@xxxxxxxxxx>
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;
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 */

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