2 files changed, 252 insertions, 3 deletions

diff --git a/lib/Makefile b/lib/Makefile
index 7c70db79c0e0..9eccea9429a7 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -4,9 +4,10 @@
 
 lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
          bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
-         kobject.o kref.o idr.o div64.o int_sqrt.o \
-         bitmap.o extable.o kobject_uevent.o prio_tree.o sha1.o \
-         halfmd4.o
+         idr.o div64.o int_sqrt.o bitmap.o extable.o prio_tree.o \
+         sha1.o halfmd4.o
+
+lib-y   += kobject.o kref.o kobject_uevent.o klist.o
 
 obj-y += sort.o parser.o
 
diff --git a/lib/klist.c b/lib/klist.c
new file mode 100644
index 000000000000..6f760424648b
--- /dev/null
+++ b/lib/klist.c
@@ -0,0 +1,248 @@
+/*
+ *      klist.c - Routines for manipulating klists.
+ *
+ *
+ *      This klist interface provides a couple of structures that wrap around 
+ *      struct list_head to provide explicit list "head" (struct klist) and 
+ *      list "node" (struct klist_node) objects. For struct klist, a spinlock
+ *      is included that protects access to the actual list itself. struct 
+ *      klist_node provides a pointer to the klist that owns it and a kref
+ *      reference count that indicates the number of current users of that node
+ *      in the list.
+ *
+ *      The entire point is to provide an interface for iterating over a list
+ *      that is safe and allows for modification of the list during the
+ *      iteration (e.g. insertion and removal), including modification of the
+ *      current node on the list.
+ *
+ *      It works using a 3rd object type - struct klist_iter - that is declared
+ *      and initialized before an iteration. klist_next() is used to acquire the
+ *      next element in the list. It returns NULL if there are no more items.
+ *      Internally, that routine takes the klist's lock, decrements the reference
+ *      count of the previous klist_node and increments the count of the next
+ *      klist_node. It then drops the lock and returns.
+ *
+ *      There are primitives for adding and removing nodes to/from a klist. 
+ *      When deleting, klist_del() will simply decrement the reference count. 
+ *      Only when the count goes to 0 is the node removed from the list. 
+ *      klist_remove() will try to delete the node from the list and block
+ *      until it is actually removed. This is useful for objects (like devices)
+ *      that have been removed from the system and must be freed (but must wait
+ *      until all accessors have finished).
+ *
+ *      Copyright (C) 2005 Patrick Mochel
+ *
+ *      This file is released under the GPL v2.
+ */
+
+#include <linux/klist.h>
+#include <linux/module.h>
+
+
+/**
+ *      klist_init - Initialize a klist structure. 
+ *      @k:     The klist we're initializing.
+ */
+
+void klist_init(struct klist * k)
+{
+        INIT_LIST_HEAD(&k->k_list);
+        spin_lock_init(&k->k_lock);
+}
+
+EXPORT_SYMBOL_GPL(klist_init);
+
+
+static void add_head(struct klist * k, struct klist_node * n)
+{
+        spin_lock(&k->k_lock);
+        list_add(&n->n_node, &k->k_list);
+        spin_unlock(&k->k_lock);
+}
+
+static void add_tail(struct klist * k, struct klist_node * n)
+{
+        spin_lock(&k->k_lock);
+        list_add_tail(&n->n_node, &k->k_list);
+        spin_unlock(&k->k_lock);
+}
+
+
+static void klist_node_init(struct klist * k, struct klist_node * n)
+{
+        INIT_LIST_HEAD(&n->n_node);
+        init_completion(&n->n_removed);
+        kref_init(&n->n_ref);
+        n->n_klist = k;
+}
+
+
+/**
+ *      klist_add_head - Initialize a klist_node and add it to front.
+ *      @k:     klist it's going on.
+ *      @n:     node we're adding.
+ */
+
+void klist_add_head(struct klist * k, struct klist_node * n)
+{
+        klist_node_init(k, n);
+        add_head(k, n);
+}
+
+EXPORT_SYMBOL_GPL(klist_add_head);
+
+
+/**
+ *      klist_add_tail - Initialize a klist_node and add it to back.
+ *      @k:     klist it's going on.
+ *      @n:     node we're adding.
+ */
+
+void klist_add_tail(struct klist * k, struct klist_node * n)
+{
+        klist_node_init(k, n);
+        add_tail(k, n);
+}
+
+EXPORT_SYMBOL_GPL(klist_add_tail);
+
+
+static void klist_release(struct kref * kref)
+{
+        struct klist_node * n = container_of(kref, struct klist_node, n_ref);
+        list_del(&n->n_node);
+        complete(&n->n_removed);
+}
+
+static int klist_dec_and_del(struct klist_node * n)
+{
+        return kref_put(&n->n_ref, klist_release);
+}
+
+
+/**
+ *      klist_del - Decrement the reference count of node and try to remove.
+ *      @n:     node we're deleting.
+ */
+
+void klist_del(struct klist_node * n)
+{
+        struct klist * k = n->n_klist;
+
+        spin_lock(&k->k_lock);
+        klist_dec_and_del(n);
+        spin_unlock(&k->k_lock);
+}
+
+EXPORT_SYMBOL_GPL(klist_del);
+
+
+/**
+ *      klist_remove - Decrement the refcount of node and wait for it to go away.
+ *      @n:     node we're removing.
+ */
+
+void klist_remove(struct klist_node * n)
+{
+        spin_lock(&n->n_klist->k_lock);
+        klist_dec_and_del(n);
+        spin_unlock(&n->n_klist->k_lock);
+        wait_for_completion(&n->n_removed);
+}
+
+EXPORT_SYMBOL_GPL(klist_remove);
+
+
+/**
+ *      klist_iter_init_node - Initialize a klist_iter structure.
+ *      @k:     klist we're iterating.
+ *      @i:     klist_iter we're filling.
+ *      @n:     node to start with.
+ *
+ *      Similar to klist_iter_init(), but starts the action off with @n, 
+ *      instead of with the list head.
+ */
+
+void klist_iter_init_node(struct klist * k, struct klist_iter * i, struct klist_node * n)
+{
+        i->i_klist = k;
+        i->i_head = &k->k_list;
+        i->i_cur = n;
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_init_node);
+
+
+/**
+ *      klist_iter_init - Iniitalize a klist_iter structure.
+ *      @k:     klist we're iterating.
+ *      @i:     klist_iter structure we're filling.
+ *
+ *      Similar to klist_iter_init_node(), but start with the list head.
+ */
+
+void klist_iter_init(struct klist * k, struct klist_iter * i)
+{
+        klist_iter_init_node(k, i, NULL);
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_init);
+
+
+/**
+ *      klist_iter_exit - Finish a list iteration.
+ *      @i:     Iterator structure.
+ *
+ *      Must be called when done iterating over list, as it decrements the 
+ *      refcount of the current node. Necessary in case iteration exited before
+ *      the end of the list was reached, and always good form.
+ */
+
+void klist_iter_exit(struct klist_iter * i)
+{
+        if (i->i_cur) {
+                klist_del(i->i_cur);
+                i->i_cur = NULL;
+        }
+}
+
+EXPORT_SYMBOL_GPL(klist_iter_exit);
+
+
+static struct klist_node * to_klist_node(struct list_head * n)
+{
+        return container_of(n, struct klist_node, n_node);
+}
+
+
+/**
+ *      klist_next - Ante up next node in list.
+ *      @i:     Iterator structure.
+ *
+ *      First grab list lock. Decrement the reference count of the previous
+ *      node, if there was one. Grab the next node, increment its reference 
+ *      count, drop the lock, and return that next node.
+ */
+
+struct klist_node * klist_next(struct klist_iter * i)
+{
+        struct list_head * next;
+        struct klist_node * knode = NULL;
+
+        spin_lock(&i->i_klist->k_lock);
+        if (i->i_cur) {
+                next = i->i_cur->n_node.next;
+                klist_dec_and_del(i->i_cur);
+        } else
+                next = i->i_head->next;
+
+        if (next != i->i_head) {
+                knode = to_klist_node(next);
+                kref_get(&knode->n_ref);
+        }
+        i->i_cur = knode;
+        spin_unlock(&i->i_klist->k_lock);
+        return knode;
+}
+
+EXPORT_SYMBOL_GPL(klist_next);