fs: use RCU read side protection in d_validate
d_validate does a purely read lookup in the dentry hash, so use RCU read side
locking instead of dcache_lock. Split out from a larget patch by
Nick Piggin <npiggin@suse.de>.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/dcache.c b/fs/dcache.c
index cc2b938..23702a9 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1491,33 +1491,26 @@
* 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 *dparent)
+int d_validate(struct dentry *dentry, struct dentry *parent)
{
- struct hlist_head *base;
- struct hlist_node *lhp;
+ struct hlist_head *head = d_hash(parent, dentry->d_name.hash);
+ struct hlist_node *node;
+ struct dentry *d;
/* Check whether the ptr might be valid at all.. */
if (!kmem_ptr_validate(dentry_cache, dentry))
- goto out;
+ return 0;
+ if (dentry->d_parent != parent)
+ return 0;
- 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);
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(d, node, head, d_hash) {
+ if (d == dentry) {
+ dget(dentry);
return 1;
}
}
- spin_unlock(&dcache_lock);
-out:
+ rcu_read_unlock();
return 0;
}
EXPORT_SYMBOL(d_validate);