2 files changed, 57 insertions, 0 deletions

diff --git a/include/linux/idr.h b/include/linux/idr.h
index 915572fa030b..8442c0bffc06 100644
--- a/include/linux/idr.h
+++ b/include/linux/idr.h
@@ -78,6 +78,8 @@ void *idr_find(struct idr *idp, int id);
 int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
 int idr_get_new(struct idr *idp, void *ptr, int *id);
 int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
+int idr_for_each(struct idr *idp,
+                 int (*fn)(int id, void *p, void *data), void *data);
 void *idr_replace(struct idr *idp, void *ptr, int id);
 void idr_remove(struct idr *idp, int id);
 void idr_destroy(struct idr *idp);
diff --git a/lib/idr.c b/lib/idr.c
index b98f01a2eb94..d29da6159dae 100644
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -437,6 +437,61 @@ void *idr_find(struct idr *idp, int id)
 EXPORT_SYMBOL(idr_find);
 
 /**
+ * idr_for_each - iterate through all stored pointers
+ * @idp: idr handle
+ * @fn: function to be called for each pointer
+ * @data: data passed back to callback function
+ *
+ * Iterate over the pointers registered with the given idr.  The
+ * callback function will be called for each pointer currently
+ * registered, passing the id, the pointer and the data pointer passed
+ * to this function.  It is not safe to modify the idr tree while in
+ * the callback, so functions such as idr_get_new and idr_remove are
+ * not allowed.
+ *
+ * We check the return of @fn each time. If it returns anything other
+ * than 0, we break out and return that value.
+ *
+ * The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
+ */
+int idr_for_each(struct idr *idp,
+                 int (*fn)(int id, void *p, void *data), void *data)
+{
+        int n, id, max, error = 0;
+        struct idr_layer *p;
+        struct idr_layer *pa[MAX_LEVEL];
+        struct idr_layer **paa = &pa[0];
+
+        n = idp->layers * IDR_BITS;
+        p = idp->top;
+        max = 1 << n;
+
+        id = 0;
+        while (id < max) {
+                while (n > 0 && p) {
+                        n -= IDR_BITS;
+                        *paa++ = p;
+                        p = p->ary[(id >> n) & IDR_MASK];
+                }
+
+                if (p) {
+                        error = fn(id, (void *)p, data);
+                        if (error)
+                                break;
+                }
+
+                id += 1 << n;
+                while (n < fls(id)) {
+                        n += IDR_BITS;
+                        p = *--paa;
+                }
+        }
+
+        return error;
+}
+EXPORT_SYMBOL(idr_for_each);
+
+/**
  * idr_replace - replace pointer for given id
  * @idp: idr handle
  * @ptr: pointer you want associated with the id