3 files changed, 81 insertions, 10 deletions

diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 4a12532da8c4..efdc94434c30 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -9,6 +9,7 @@
 #include <linux/seqlock.h>
 #include <linux/cache.h>
 #include <linux/rcupdate.h>
+#include <linux/lockref.h>
 
 struct nameidata;
 struct path;
@@ -100,6 +101,8 @@ extern unsigned int full_name_hash(const unsigned char *, unsigned int);
 # endif
 #endif
 
+#define d_lock  d_lockref.lock
+
 struct dentry {
         /* RCU lookup touched fields */
         unsigned int d_flags;           /* protected by d_lock */
@@ -112,8 +115,7 @@ struct dentry {
         unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */
 
         /* Ref lookup also touches following */
-        unsigned int d_count;           /* protected by d_lock */
-        spinlock_t d_lock;              /* per dentry lock */
+        struct lockref d_lockref;       /* per-dentry lock and refcount */
         const struct dentry_operations *d_op;
         struct super_block *d_sb;       /* The root of the dentry tree */
         unsigned long d_time;           /* used by d_revalidate */
@@ -318,7 +320,7 @@ static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
         assert_spin_locked(&dentry->d_lock);
         if (!read_seqcount_retry(&dentry->d_seq, seq)) {
                 ret = 1;
-                dentry->d_count++;
+                dentry->d_lockref.count++;
         }
 
         return ret;
@@ -326,7 +328,7 @@ static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 
 static inline unsigned d_count(const struct dentry *dentry)
 {
-        return dentry->d_count;
+        return dentry->d_lockref.count;
 }
 
 /* validate "insecure" dentry pointer */
@@ -357,17 +359,14 @@ extern char *dentry_path(struct dentry *, char *, int);
 static inline struct dentry *dget_dlock(struct dentry *dentry)
 {
         if (dentry)
-                dentry->d_count++;
+                dentry->d_lockref.count++;
         return dentry;
 }
 
 static inline struct dentry *dget(struct dentry *dentry)
 {
-        if (dentry) {
-                spin_lock(&dentry->d_lock);
-                dget_dlock(dentry);
-                spin_unlock(&dentry->d_lock);
-        }
+        if (dentry)
+                lockref_get(&dentry->d_lockref);
         return dentry;
 }
 
diff --git a/include/linux/lockref.h b/include/linux/lockref.h
new file mode 100644
index 000000000000..01233e01627a
--- /dev/null
+++ b/include/linux/lockref.h
@@ -0,0 +1,71 @@
+#ifndef __LINUX_LOCKREF_H
+#define __LINUX_LOCKREF_H
+
+/*
+ * Locked reference counts.
+ *
+ * These are different from just plain atomic refcounts in that they
+ * are atomic with respect to the spinlock that goes with them.  In
+ * particular, there can be implementations that don't actually get
+ * the spinlock for the common decrement/increment operations, but they
+ * still have to check that the operation is done semantically as if
+ * the spinlock had been taken (using a cmpxchg operation that covers
+ * both the lock and the count word, or using memory transactions, for
+ * example).
+ */
+
+#include <linux/spinlock.h>
+
+struct lockref {
+        spinlock_t lock;
+        unsigned int count;
+};
+
+/**
+ * lockref_get - Increments reference count unconditionally
+ * @lockcnt: pointer to lockref structure
+ *
+ * This operation is only valid if you already hold a reference
+ * to the object, so you know the count cannot be zero.
+ */
+static inline void lockref_get(struct lockref *lockref)
+{
+        spin_lock(&lockref->lock);
+        lockref->count++;
+        spin_unlock(&lockref->lock);
+}
+
+/**
+ * lockref_get_not_zero - Increments count unless the count is 0
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count is 0
+ */
+static inline int lockref_get_not_zero(struct lockref *lockref)
+{
+        int retval = 0;
+
+        spin_lock(&lockref->lock);
+        if (lockref->count) {
+                lockref->count++;
+                retval = 1;
+        }
+        spin_unlock(&lockref->lock);
+        return retval;
+}
+
+/**
+ * lockref_put_or_lock - decrements count unless count <= 1 before decrement
+ * @lockcnt: pointer to lockref structure
+ * Return: 1 if count updated successfully or 0 if count <= 1 and lock taken
+ */
+static inline int lockref_put_or_lock(struct lockref *lockref)
+{
+        spin_lock(&lockref->lock);
+        if (lockref->count <= 1)
+                return 0;
+        lockref->count--;
+        spin_unlock(&lockref->lock);
+        return 1;
+}
+
+#endif /* __LINUX_LOCKREF_H */
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index 580a5320cc96..6d91fcb4c5cb 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -16,6 +16,7 @@
 #include <linux/list.h>
 #include <linux/rbtree.h>
 #include <linux/err.h>
+#include <linux/bug.h>
 
 struct module;
 struct device;