ida: simplified functions for id allocation

The current hyper-optimized functions are overkill if you simply want to
allocate an id for a device.  Create versions which use an internal
lock.

In followup patches, numerous drivers are converted to use this
interface.

Thanks to Tejun for feedback.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 13a801f3d028225533f2ce701349b2b0657ca734..255491cf522e1d08ea6d0066fc7872f32817c82c 100644 (file)
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -146,6 +146,10 @@ void ida_remove(struct ida *ida, int id);
 void ida_destroy(struct ida *ida);
 void ida_init(struct ida *ida);
 
+int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
+                  gfp_t gfp_mask);
+void ida_simple_remove(struct ida *ida, unsigned int id);
+
 void __init idr_init_cache(void);
 
 #endif /* __IDR_H__ */

diff --git a/lib/idr.c b/lib/idr.c
index e15502e8b21e5bbb47addef5c8fea61b57118508..db040ce3fa73a328a118a93097d6e5062c16409d 100644 (file)
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -34,8 +34,10 @@
 #include <linux/err.h>
 #include <linux/string.h>
 #include <linux/idr.h>
+#include <linux/spinlock.h>
 
 static struct kmem_cache *idr_layer_cache;
+static DEFINE_SPINLOCK(simple_ida_lock);
 
 static struct idr_layer *get_from_free_list(struct idr *idp)
 {
@@ -925,6 +927,71 @@ void ida_destroy(struct ida *ida)
 }
 EXPORT_SYMBOL(ida_destroy);
 
+/**
+ * ida_simple_get - get a new id.
+ * @ida: the (initialized) ida.
+ * @start: the minimum id (inclusive, < 0x8000000)
+ * @end: the maximum id (exclusive, < 0x8000000 or 0)
+ * @gfp_mask: memory allocation flags
+ *
+ * Allocates an id in the range start <= id < end, or returns -ENOSPC.
+ * On memory allocation failure, returns -ENOMEM.
+ *
+ * Use ida_simple_remove() to get rid of an id.
+ */
+int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
+                  gfp_t gfp_mask)
+{
+       int ret, id;
+       unsigned int max;
+
+       BUG_ON((int)start < 0);
+       BUG_ON((int)end < 0);
+
+       if (end == 0)
+               max = 0x80000000;
+       else {
+               BUG_ON(end < start);
+               max = end - 1;
+       }
+
+again:
+       if (!ida_pre_get(ida, gfp_mask))
+               return -ENOMEM;
+
+       spin_lock(&simple_ida_lock);
+       ret = ida_get_new_above(ida, start, &id);
+       if (!ret) {
+               if (id > max) {
+                       ida_remove(ida, id);
+                       ret = -ENOSPC;
+               } else {
+                       ret = id;
+               }
+       }
+       spin_unlock(&simple_ida_lock);
+
+       if (unlikely(ret == -EAGAIN))
+               goto again;
+
+       return ret;
+}
+EXPORT_SYMBOL(ida_simple_get);
+
+/**
+ * ida_simple_remove - remove an allocated id.
+ * @ida: the (initialized) ida.
+ * @id: the id returned by ida_simple_get.
+ */
+void ida_simple_remove(struct ida *ida, unsigned int id)
+{
+       BUG_ON((int)id < 0);
+       spin_lock(&simple_ida_lock);
+       ida_remove(ida, id);
+       spin_unlock(&simple_ida_lock);
+}
+EXPORT_SYMBOL(ida_simple_remove);
+
 /**
  * ida_init - initialize ida handle
  * @ida:       ida handle