percpu_ida: add percpu_ida_for_each_free

Add a new API to iterate free ids. blk-mq-tag will use it.

Note, this doesn't guarantee to iterate all free ids restrictly. Caller
should be aware of this. blk-mq uses it to do sanity check for request
timedout, so can tolerate the limitation.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

2 files changed, 48 insertions, 0 deletions

diff --git a/include/linux/percpu_ida.h b/include/linux/percpu_ida.h
index 56c14033e7e7..63510ae6f933 100644
--- a/include/linux/percpu_ida.h
+++ b/include/linux/percpu_ida.h
@@ -73,4 +73,8 @@ static inline int percpu_ida_init(struct percpu_ida *pool, unsigned long nr_tags
                 IDA_DEFAULT_PCPU_BATCH_MOVE);
 }
 
+typedef int (*percpu_ida_cb)(unsigned, void *);
+int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
+        void *data);
+
 #endif /* __PERCPU_IDA_H__ */
diff --git a/lib/percpu_ida.c b/lib/percpu_ida.c
index a601d4259e13..0f51c1b556cf 100644
--- a/lib/percpu_ida.c
+++ b/lib/percpu_ida.c
@@ -327,3 +327,47 @@ err:
         return -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(__percpu_ida_init);
+
+/**
+ * percpu_ida_for_each_free - iterate free ids of a pool
+ * @pool: pool to iterate
+ * @fn: interate callback function
+ * @data: parameter for @fn
+ *
+ * Note, this doesn't guarantee to iterate all free ids restrictly. Some free
+ * ids might be missed, some might be iterated duplicated, and some might
+ * be iterated and not free soon.
+ */
+int percpu_ida_for_each_free(struct percpu_ida *pool, percpu_ida_cb fn,
+        void *data)
+{
+        unsigned long flags;
+        struct percpu_ida_cpu *remote;
+        unsigned cpu, i, err = 0;
+
+        local_irq_save(flags);
+        for_each_possible_cpu(cpu) {
+                remote = per_cpu_ptr(pool->tag_cpu, cpu);
+                spin_lock(&remote->lock);
+                for (i = 0; i < remote->nr_free; i++) {
+                        err = fn(remote->freelist[i], data);
+                        if (err)
+                                break;
+                }
+                spin_unlock(&remote->lock);
+                if (err)
+                        goto out;
+        }
+
+        spin_lock(&pool->lock);
+        for (i = 0; i < pool->nr_free; i++) {
+                err = fn(pool->freelist[i], data);
+                if (err)
+                        break;
+        }
+        spin_unlock(&pool->lock);
+out:
+        local_irq_restore(flags);
+        return err;
+}
+EXPORT_SYMBOL_GPL(percpu_ida_for_each_free);