1 files changed, 79 insertions, 0 deletions
diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs_cpu.h b/drivers/staging/lustre/include/linux/libcfs/libcfs_cpu.h
index 9e62c59714b7..81d8079e3b5e 100644
--- a/drivers/staging/lustre/include/linux/libcfs/libcfs_cpu.h
+++ b/drivers/staging/lustre/include/linux/libcfs/libcfs_cpu.h
@@ -203,6 +203,85 @@ int cfs_cpt_spread_node(struct cfs_cpt_table *cptab, int cpt);
  */
 int cfs_cpu_ht_nsiblings(int cpu);
 
+/*
+ * allocate per-cpu-partition data, returned value is an array of pointers,
+ * variable can be indexed by CPU ID.
+ *	cptab != NULL: size of array is number of CPU partitions
+ *	cptab == NULL: size of array is number of HW cores
+ */
+void *cfs_percpt_alloc(struct cfs_cpt_table *cptab, unsigned int size);
+/*
+ * destory per-cpu-partition variable
+ */
+void cfs_percpt_free(void *vars);
+int cfs_percpt_number(void *vars);
+
+#define cfs_percpt_for_each(var, i, vars)		\
+	for (i = 0; i < cfs_percpt_number(vars) &&	\
+		((var) = (vars)[i]) != NULL; i++)
+
+/*
+ * percpu partition lock
+ *
+ * There are some use-cases like this in Lustre:
+ * . each CPU partition has it's own private data which is frequently changed,
+ *   and mostly by the local CPU partition.
+ * . all CPU partitions share some global data, these data are rarely changed.
+ *
+ * LNet is typical example.
+ * CPU partition lock is designed for this kind of use-cases:
+ * . each CPU partition has it's own private lock
+ * . change on private data just needs to take the private lock
+ * . read on shared data just needs to take _any_ of private locks
+ * . change on shared data needs to take _all_ private locks,
+ *   which is slow and should be really rare.
+ */
+enum {
+	CFS_PERCPT_LOCK_EX	= -1,	/* negative */
+};
+
+struct cfs_percpt_lock {
+	/* cpu-partition-table for this lock */
+	struct cfs_cpt_table     *pcl_cptab;
+	/* exclusively locked */
+	unsigned int		  pcl_locked;
+	/* private lock table */
+	spinlock_t		**pcl_locks;
+};
+
+/* return number of private locks */
+#define cfs_percpt_lock_num(pcl)	cfs_cpt_number(pcl->pcl_cptab)
+
+/*
+ * create a cpu-partition lock based on CPU partition table \a cptab,
+ * each private lock has extra \a psize bytes padding data
+ */
+struct cfs_percpt_lock *cfs_percpt_lock_create(struct cfs_cpt_table *cptab,
+					       struct lock_class_key *keys);
+/* destroy a cpu-partition lock */
+void cfs_percpt_lock_free(struct cfs_percpt_lock *pcl);
+
+/* lock private lock \a index of \a pcl */
+void cfs_percpt_lock(struct cfs_percpt_lock *pcl, int index);
+
+/* unlock private lock \a index of \a pcl */
+void cfs_percpt_unlock(struct cfs_percpt_lock *pcl, int index);
+
+#define CFS_PERCPT_LOCK_KEYS	256
+
+/* NB: don't allocate keys dynamically, lockdep needs them to be in ".data" */
+#define cfs_percpt_lock_alloc(cptab)					\
+({									\
+	static struct lock_class_key ___keys[CFS_PERCPT_LOCK_KEYS];	\
+	struct cfs_percpt_lock *___lk;					\
+									\
+	if (cfs_cpt_number(cptab) > CFS_PERCPT_LOCK_KEYS)		\
+		___lk = cfs_percpt_lock_create(cptab, NULL);		\
+	else								\
+		___lk = cfs_percpt_lock_create(cptab, ___keys);		\
+	___lk;								\
+})
+
 /**
  * iterate over all CPU partitions in \a cptab
  */