#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/spinlock.h>
+#include <linux/seqlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
unsigned int d_count; /* protected by d_lock */
unsigned int d_flags; /* protected by d_lock */
spinlock_t d_lock; /* per dentry lock */
+ seqcount_t d_seq; /* per dentry seqlock */
int d_mounted;
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
/* appendix may either be NULL or be used for transname suffixes */
-extern struct dentry * d_lookup(struct dentry *, struct qstr *);
-extern struct dentry * __d_lookup(struct dentry *, struct qstr *);
-extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
+extern struct dentry *d_lookup(struct dentry *, struct qstr *);
+extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
+extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
+extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
+ unsigned *seq, struct inode **inode);
+
+/**
+ * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
+ * @dentry: dentry to take a ref on
+ * @seq: seqcount to verify against
+ * @Returns: 0 on failure, else 1.
+ *
+ * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
+ * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
+ */
+static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
+{
+ int ret = 0;
+
+ assert_spin_locked(&dentry->d_lock);
+ if (!read_seqcount_retry(&dentry->d_seq, seq)) {
+ ret = 1;
+ dentry->d_count++;
+ }
+
+ return ret;
+}
/* validate "insecure" dentry pointer */
extern int d_validate(struct dentry *, struct dentry *);