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From: John Stultz on 30 Jun 2010 15:20
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(a)us.ibm.com>
CC: Thomas Gleixner <tglx(a)linutronix.de>
CC: Nick Piggin <npiggin(a)suse.de>
CC: Peter Zijlstra <peterz(a)infradead.org>
CC: John Kacur <jkacur(a)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

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