From d3a23e1678a5827c38ed8a465ad91d65e59fa911 Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@kernel.dk>
Date: Wed, 5 Jan 2011 20:01:21 +1100
Subject: [PATCH] Revert "fs: use RCU read side protection in d_validate"
This reverts commit 3825bdb7ed920845961f32f364454bee5f469abb.
You cannot dget() a dentry without having a reference, or holding
a lock that guarantees it remains valid.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
---
fs/dcache.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 23702a9d4e6d..cc2b93802179 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1491,26 +1491,33 @@ out:
* This is used by ncpfs in its readdir implementation.
* Zero is returned in the dentry is invalid.
*/
-int d_validate(struct dentry *dentry, struct dentry *parent)
+
+int d_validate(struct dentry *dentry, struct dentry *dparent)
{
- struct hlist_head *head = d_hash(parent, dentry->d_name.hash);
- struct hlist_node *node;
- struct dentry *d;
+ struct hlist_head *base;
+ struct hlist_node *lhp;
/* Check whether the ptr might be valid at all.. */
if (!kmem_ptr_validate(dentry_cache, dentry))
- return 0;
- if (dentry->d_parent != parent)
- return 0;
+ goto out;
- rcu_read_lock();
- hlist_for_each_entry_rcu(d, node, head, d_hash) {
- if (d == dentry) {
- dget(dentry);
+ if (dentry->d_parent != dparent)
+ goto out;
+
+ spin_lock(&dcache_lock);
+ base = d_hash(dparent, dentry->d_name.hash);
+ hlist_for_each(lhp,base) {
+ /* hlist_for_each_entry_rcu() not required for d_hash list
+ * as it is parsed under dcache_lock
+ */
+ if (dentry == hlist_entry(lhp, struct dentry, d_hash)) {
+ __dget_locked(dentry);
+ spin_unlock(&dcache_lock);
return 1;
}
}
- rcu_read_unlock();
+ spin_unlock(&dcache_lock);
+out:
return 0;
}
EXPORT_SYMBOL(d_validate);
--
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