fs: rcu-walk for path lookup

[karo-tx-linux.git] / include / linux / dcache.h

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index ca648685f0cc9a3575fcbfe9c2353f28a4918625..c2e7390289ccc7d7a0944ff65b517f681f7ae823 100644 (file)
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -5,6 +5,7 @@
 #include <linux/list.h>
 #include <linux/rculist.h>
 #include <linux/spinlock.h>
+#include <linux/seqlock.h>
 #include <linux/cache.h>
 #include <linux/rcupdate.h>
 
@@ -90,6 +91,7 @@ struct dentry {
        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 */
@@ -266,9 +268,33 @@ extern void d_move(struct dentry *, struct dentry *);
 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 *);