lib: add idr_for_each()

This patch adds an iterator function for the idr data structure.  Compared
to just iterating through the idr with an integer and idr_find, this
iterator is (almost, but not quite) linear in the number of elements, as
opposed to the number of integers in the range covered by the idr.  This
makes a difference for sparse idrs, but more importantly, it's a nicer way
to iterate through the elements.

The drm subsystem is moving to idr for tracking contexts and drawables, and
with this change, we can use the idr exclusively for tracking these
resources.

[akpm@linux-foundation.org: fix comment]
Signed-off-by: Kristian Hoegsberg <krh@redhat.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Dave Airlie <airlied@linux.ie>
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 915572fa030b678835732a166b0f7b86e4dc1fb6..8442c0bffc06cac5a847f28acf826e8b4a7c4779 100644 (file)
--- 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 b98f01a2eb946b221f5d7d7d193422f95e607a3a..d29da6159dae0637f5da6042c369ec609207b7de 100644 (file)
--- a/lib/idr.c
+++ b/lib/idr.c
@@ -436,6 +436,61 @@ 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