Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 1038 insertions, 0 deletions

diff --git a/lib/objagg.c b/lib/objagg.c
new file mode 100644
index 000000000..23c7105a3
--- /dev/null
+++ b/lib/objagg.c
@@ -0,0 +1,1038 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/* Copyright (c) 2018 Mellanox Technologies. All rights reserved */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/rhashtable.h>
+#include <linux/idr.h>
+#include <linux/list.h>
+#include <linux/sort.h>
+#include <linux/objagg.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/objagg.h>
+
+struct objagg_hints {
+	struct rhashtable node_ht;
+	struct rhashtable_params ht_params;
+	struct list_head node_list;
+	unsigned int node_count;
+	unsigned int root_count;
+	unsigned int refcount;
+	const struct objagg_ops *ops;
+};
+
+struct objagg_hints_node {
+	struct rhash_head ht_node; /* member of objagg_hints->node_ht */
+	struct list_head list; /* member of objagg_hints->node_list */
+	struct objagg_hints_node *parent;
+	unsigned int root_id;
+	struct objagg_obj_stats_info stats_info;
+	unsigned long obj[];
+};
+
+static struct objagg_hints_node *
+objagg_hints_lookup(struct objagg_hints *objagg_hints, void *obj)
+{
+	if (!objagg_hints)
+		return NULL;
+	return rhashtable_lookup_fast(&objagg_hints->node_ht, obj,
+				      objagg_hints->ht_params);
+}
+
+struct objagg {
+	const struct objagg_ops *ops;
+	void *priv;
+	struct rhashtable obj_ht;
+	struct rhashtable_params ht_params;
+	struct list_head obj_list;
+	unsigned int obj_count;
+	struct ida root_ida;
+	struct objagg_hints *hints;
+};
+
+struct objagg_obj {
+	struct rhash_head ht_node; /* member of objagg->obj_ht */
+	struct list_head list; /* member of objagg->obj_list */
+	struct objagg_obj *parent; /* if the object is nested, this
+				    * holds pointer to parent, otherwise NULL
+				    */
+	union {
+		void *delta_priv; /* user delta private */
+		void *root_priv; /* user root private */
+	};
+	unsigned int root_id;
+	unsigned int refcount; /* counts number of users of this object
+				* including nested objects
+				*/
+	struct objagg_obj_stats stats;
+	unsigned long obj[];
+};
+
+static unsigned int objagg_obj_ref_inc(struct objagg_obj *objagg_obj)
+{
+	return ++objagg_obj->refcount;
+}
+
+static unsigned int objagg_obj_ref_dec(struct objagg_obj *objagg_obj)
+{
+	return --objagg_obj->refcount;
+}
+
+static void objagg_obj_stats_inc(struct objagg_obj *objagg_obj)
+{
+	objagg_obj->stats.user_count++;
+	objagg_obj->stats.delta_user_count++;
+	if (objagg_obj->parent)
+		objagg_obj->parent->stats.delta_user_count++;
+}
+
+static void objagg_obj_stats_dec(struct objagg_obj *objagg_obj)
+{
+	objagg_obj->stats.user_count--;
+	objagg_obj->stats.delta_user_count--;
+	if (objagg_obj->parent)
+		objagg_obj->parent->stats.delta_user_count--;
+}
+
+static bool objagg_obj_is_root(const struct objagg_obj *objagg_obj)
+{
+	/* Nesting is not supported, so we can use ->parent
+	 * to figure out if the object is root.
+	 */
+	return !objagg_obj->parent;
+}
+
+/**
+ * objagg_obj_root_priv - obtains root private for an object
+ * @objagg_obj:	objagg object instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * Either the object is root itself when the private is returned
+ * directly, or the parent is root and its private is returned
+ * instead.
+ *
+ * Returns a user private root pointer.
+ */
+const void *objagg_obj_root_priv(const struct objagg_obj *objagg_obj)
+{
+	if (objagg_obj_is_root(objagg_obj))
+		return objagg_obj->root_priv;
+	WARN_ON(!objagg_obj_is_root(objagg_obj->parent));
+	return objagg_obj->parent->root_priv;
+}
+EXPORT_SYMBOL(objagg_obj_root_priv);
+
+/**
+ * objagg_obj_delta_priv - obtains delta private for an object
+ * @objagg_obj:	objagg object instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * Returns user private delta pointer or NULL in case the passed
+ * object is root.
+ */
+const void *objagg_obj_delta_priv(const struct objagg_obj *objagg_obj)
+{
+	if (objagg_obj_is_root(objagg_obj))
+		return NULL;
+	return objagg_obj->delta_priv;
+}
+EXPORT_SYMBOL(objagg_obj_delta_priv);
+
+/**
+ * objagg_obj_raw - obtains object user private pointer
+ * @objagg_obj:	objagg object instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * Returns user private pointer as was passed to objagg_obj_get() by "obj" arg.
+ */
+const void *objagg_obj_raw(const struct objagg_obj *objagg_obj)
+{
+	return objagg_obj->obj;
+}
+EXPORT_SYMBOL(objagg_obj_raw);
+
+static struct objagg_obj *objagg_obj_lookup(struct objagg *objagg, void *obj)
+{
+	return rhashtable_lookup_fast(&objagg->obj_ht, obj, objagg->ht_params);
+}
+
+static int objagg_obj_parent_assign(struct objagg *objagg,
+				    struct objagg_obj *objagg_obj,
+				    struct objagg_obj *parent,
+				    bool take_parent_ref)
+{
+	void *delta_priv;
+
+	if (WARN_ON(!objagg_obj_is_root(parent)))
+		return -EINVAL;
+
+	delta_priv = objagg->ops->delta_create(objagg->priv, parent->obj,
+					       objagg_obj->obj);
+	if (IS_ERR(delta_priv))
+		return PTR_ERR(delta_priv);
+
+	/* User returned a delta private, that means that
+	 * our object can be aggregated into the parent.
+	 */
+	objagg_obj->parent = parent;
+	objagg_obj->delta_priv = delta_priv;
+	if (take_parent_ref)
+		objagg_obj_ref_inc(objagg_obj->parent);
+	trace_objagg_obj_parent_assign(objagg, objagg_obj,
+				       parent,
+				       parent->refcount);
+	return 0;
+}
+
+static int objagg_obj_parent_lookup_assign(struct objagg *objagg,
+					   struct objagg_obj *objagg_obj)
+{
+	struct objagg_obj *objagg_obj_cur;
+	int err;
+
+	list_for_each_entry(objagg_obj_cur, &objagg->obj_list, list) {
+		/* Nesting is not supported. In case the object
+		 * is not root, it cannot be assigned as parent.
+		 */
+		if (!objagg_obj_is_root(objagg_obj_cur))
+			continue;
+		err = objagg_obj_parent_assign(objagg, objagg_obj,
+					       objagg_obj_cur, true);
+		if (!err)
+			return 0;
+	}
+	return -ENOENT;
+}
+
+static void __objagg_obj_put(struct objagg *objagg,
+			     struct objagg_obj *objagg_obj);
+
+static void objagg_obj_parent_unassign(struct objagg *objagg,
+				       struct objagg_obj *objagg_obj)
+{
+	trace_objagg_obj_parent_unassign(objagg, objagg_obj,
+					 objagg_obj->parent,
+					 objagg_obj->parent->refcount);
+	objagg->ops->delta_destroy(objagg->priv, objagg_obj->delta_priv);
+	__objagg_obj_put(objagg, objagg_obj->parent);
+}
+
+static int objagg_obj_root_id_alloc(struct objagg *objagg,
+				    struct objagg_obj *objagg_obj,
+				    struct objagg_hints_node *hnode)
+{
+	unsigned int min, max;
+	int root_id;
+
+	/* In case there are no hints available, the root id is invalid. */
+	if (!objagg->hints) {
+		objagg_obj->root_id = OBJAGG_OBJ_ROOT_ID_INVALID;
+		return 0;
+	}
+
+	if (hnode) {
+		min = hnode->root_id;
+		max = hnode->root_id;
+	} else {
+		/* For objects with no hint, start after the last
+		 * hinted root_id.
+		 */
+		min = objagg->hints->root_count;
+		max = ~0;
+	}
+
+	root_id = ida_alloc_range(&objagg->root_ida, min, max, GFP_KERNEL);
+
+	if (root_id < 0)
+		return root_id;
+	objagg_obj->root_id = root_id;
+	return 0;
+}
+
+static void objagg_obj_root_id_free(struct objagg *objagg,
+				    struct objagg_obj *objagg_obj)
+{
+	if (!objagg->hints)
+		return;
+	ida_free(&objagg->root_ida, objagg_obj->root_id);
+}
+
+static int objagg_obj_root_create(struct objagg *objagg,
+				  struct objagg_obj *objagg_obj,
+				  struct objagg_hints_node *hnode)
+{
+	int err;
+
+	err = objagg_obj_root_id_alloc(objagg, objagg_obj, hnode);
+	if (err)
+		return err;
+	objagg_obj->root_priv = objagg->ops->root_create(objagg->priv,
+							 objagg_obj->obj,
+							 objagg_obj->root_id);
+	if (IS_ERR(objagg_obj->root_priv)) {
+		err = PTR_ERR(objagg_obj->root_priv);
+		goto err_root_create;
+	}
+	trace_objagg_obj_root_create(objagg, objagg_obj);
+	return 0;
+
+err_root_create:
+	objagg_obj_root_id_free(objagg, objagg_obj);
+	return err;
+}
+
+static void objagg_obj_root_destroy(struct objagg *objagg,
+				    struct objagg_obj *objagg_obj)
+{
+	trace_objagg_obj_root_destroy(objagg, objagg_obj);
+	objagg->ops->root_destroy(objagg->priv, objagg_obj->root_priv);
+	objagg_obj_root_id_free(objagg, objagg_obj);
+}
+
+static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj);
+
+static int objagg_obj_init_with_hints(struct objagg *objagg,
+				      struct objagg_obj *objagg_obj,
+				      bool *hint_found)
+{
+	struct objagg_hints_node *hnode;
+	struct objagg_obj *parent;
+	int err;
+
+	hnode = objagg_hints_lookup(objagg->hints, objagg_obj->obj);
+	if (!hnode) {
+		*hint_found = false;
+		return 0;
+	}
+	*hint_found = true;
+
+	if (!hnode->parent)
+		return objagg_obj_root_create(objagg, objagg_obj, hnode);
+
+	parent = __objagg_obj_get(objagg, hnode->parent->obj);
+	if (IS_ERR(parent))
+		return PTR_ERR(parent);
+
+	err = objagg_obj_parent_assign(objagg, objagg_obj, parent, false);
+	if (err) {
+		*hint_found = false;
+		err = 0;
+		goto err_parent_assign;
+	}
+
+	return 0;
+
+err_parent_assign:
+	objagg_obj_put(objagg, parent);
+	return err;
+}
+
+static int objagg_obj_init(struct objagg *objagg,
+			   struct objagg_obj *objagg_obj)
+{
+	bool hint_found;
+	int err;
+
+	/* First, try to use hints if they are available and
+	 * if they provide result.
+	 */
+	err = objagg_obj_init_with_hints(objagg, objagg_obj, &hint_found);
+	if (err)
+		return err;
+
+	if (hint_found)
+		return 0;
+
+	/* Try to find if the object can be aggregated under an existing one. */
+	err = objagg_obj_parent_lookup_assign(objagg, objagg_obj);
+	if (!err)
+		return 0;
+	/* If aggregation is not possible, make the object a root. */
+	return objagg_obj_root_create(objagg, objagg_obj, NULL);
+}
+
+static void objagg_obj_fini(struct objagg *objagg,
+			    struct objagg_obj *objagg_obj)
+{
+	if (!objagg_obj_is_root(objagg_obj))
+		objagg_obj_parent_unassign(objagg, objagg_obj);
+	else
+		objagg_obj_root_destroy(objagg, objagg_obj);
+}
+
+static struct objagg_obj *objagg_obj_create(struct objagg *objagg, void *obj)
+{
+	struct objagg_obj *objagg_obj;
+	int err;
+
+	objagg_obj = kzalloc(sizeof(*objagg_obj) + objagg->ops->obj_size,
+			     GFP_KERNEL);
+	if (!objagg_obj)
+		return ERR_PTR(-ENOMEM);
+	objagg_obj_ref_inc(objagg_obj);
+	memcpy(objagg_obj->obj, obj, objagg->ops->obj_size);
+
+	err = objagg_obj_init(objagg, objagg_obj);
+	if (err)
+		goto err_obj_init;
+
+	err = rhashtable_insert_fast(&objagg->obj_ht, &objagg_obj->ht_node,
+				     objagg->ht_params);
+	if (err)
+		goto err_ht_insert;
+	list_add(&objagg_obj->list, &objagg->obj_list);
+	objagg->obj_count++;
+	trace_objagg_obj_create(objagg, objagg_obj);
+
+	return objagg_obj;
+
+err_ht_insert:
+	objagg_obj_fini(objagg, objagg_obj);
+err_obj_init:
+	kfree(objagg_obj);
+	return ERR_PTR(err);
+}
+
+static struct objagg_obj *__objagg_obj_get(struct objagg *objagg, void *obj)
+{
+	struct objagg_obj *objagg_obj;
+
+	/* First, try to find the object exactly as user passed it,
+	 * perhaps it is already in use.
+	 */
+	objagg_obj = objagg_obj_lookup(objagg, obj);
+	if (objagg_obj) {
+		objagg_obj_ref_inc(objagg_obj);
+		return objagg_obj;
+	}
+
+	return objagg_obj_create(objagg, obj);
+}
+
+/**
+ * objagg_obj_get - gets an object within objagg instance
+ * @objagg:	objagg instance
+ * @obj:	user-specific private object pointer
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * Size of the "obj" memory is specified in "objagg->ops".
+ *
+ * There are 3 main options this function wraps:
+ * 1) The object according to "obj" already exist. In that case
+ *    the reference counter is incremented and the object is returned.
+ * 2) The object does not exist, but it can be aggregated within
+ *    another object. In that case, user ops->delta_create() is called
+ *    to obtain delta data and a new object is created with returned
+ *    user-delta private pointer.
+ * 3) The object does not exist and cannot be aggregated into
+ *    any of the existing objects. In that case, user ops->root_create()
+ *    is called to create the root and a new object is created with
+ *    returned user-root private pointer.
+ *
+ * Returns a pointer to objagg object instance in case of success,
+ * otherwise it returns pointer error using ERR_PTR macro.
+ */
+struct objagg_obj *objagg_obj_get(struct objagg *objagg, void *obj)
+{
+	struct objagg_obj *objagg_obj;
+
+	objagg_obj = __objagg_obj_get(objagg, obj);
+	if (IS_ERR(objagg_obj))
+		return objagg_obj;
+	objagg_obj_stats_inc(objagg_obj);
+	trace_objagg_obj_get(objagg, objagg_obj, objagg_obj->refcount);
+	return objagg_obj;
+}
+EXPORT_SYMBOL(objagg_obj_get);
+
+static void objagg_obj_destroy(struct objagg *objagg,
+			       struct objagg_obj *objagg_obj)
+{
+	trace_objagg_obj_destroy(objagg, objagg_obj);
+	--objagg->obj_count;
+	list_del(&objagg_obj->list);
+	rhashtable_remove_fast(&objagg->obj_ht, &objagg_obj->ht_node,
+			       objagg->ht_params);
+	objagg_obj_fini(objagg, objagg_obj);
+	kfree(objagg_obj);
+}
+
+static void __objagg_obj_put(struct objagg *objagg,
+			     struct objagg_obj *objagg_obj)
+{
+	if (!objagg_obj_ref_dec(objagg_obj))
+		objagg_obj_destroy(objagg, objagg_obj);
+}
+
+/**
+ * objagg_obj_put - puts an object within objagg instance
+ * @objagg:	objagg instance
+ * @objagg_obj:	objagg object instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * Symmetric to objagg_obj_get().
+ */
+void objagg_obj_put(struct objagg *objagg, struct objagg_obj *objagg_obj)
+{
+	trace_objagg_obj_put(objagg, objagg_obj, objagg_obj->refcount);
+	objagg_obj_stats_dec(objagg_obj);
+	__objagg_obj_put(objagg, objagg_obj);
+}
+EXPORT_SYMBOL(objagg_obj_put);
+
+/**
+ * objagg_create - creates a new objagg instance
+ * @ops:		user-specific callbacks
+ * @objagg_hints:	hints, can be NULL
+ * @priv:		pointer to a private data passed to the ops
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * The purpose of the library is to provide an infrastructure to
+ * aggregate user-specified objects. Library does not care about the type
+ * of the object. User fills-up ops which take care of the specific
+ * user object manipulation.
+ *
+ * As a very stupid example, consider integer numbers. For example
+ * number 8 as a root object. That can aggregate number 9 with delta 1,
+ * number 10 with delta 2, etc. This example is implemented as
+ * a part of a testing module in test_objagg.c file.
+ *
+ * Each objagg instance contains multiple trees. Each tree node is
+ * represented by "an object". In the current implementation there can be
+ * only roots and leafs nodes. Leaf nodes are called deltas.
+ * But in general, this can be easily extended for intermediate nodes.
+ * In that extension, a delta would be associated with all non-root
+ * nodes.
+ *
+ * Returns a pointer to newly created objagg instance in case of success,
+ * otherwise it returns pointer error using ERR_PTR macro.
+ */
+struct objagg *objagg_create(const struct objagg_ops *ops,
+			     struct objagg_hints *objagg_hints, void *priv)
+{
+	struct objagg *objagg;
+	int err;
+
+	if (WARN_ON(!ops || !ops->root_create || !ops->root_destroy ||
+		    !ops->delta_check || !ops->delta_create ||
+		    !ops->delta_destroy))
+		return ERR_PTR(-EINVAL);
+
+	objagg = kzalloc_obj(*objagg);
+	if (!objagg)
+		return ERR_PTR(-ENOMEM);
+	objagg->ops = ops;
+	if (objagg_hints) {
+		objagg->hints = objagg_hints;
+		objagg_hints->refcount++;
+	}
+	objagg->priv = priv;
+	INIT_LIST_HEAD(&objagg->obj_list);
+
+	objagg->ht_params.key_len = ops->obj_size;
+	objagg->ht_params.key_offset = offsetof(struct objagg_obj, obj);
+	objagg->ht_params.head_offset = offsetof(struct objagg_obj, ht_node);
+
+	err = rhashtable_init(&objagg->obj_ht, &objagg->ht_params);
+	if (err)
+		goto err_rhashtable_init;
+
+	ida_init(&objagg->root_ida);
+
+	trace_objagg_create(objagg);
+	return objagg;
+
+err_rhashtable_init:
+	kfree(objagg);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(objagg_create);
+
+/**
+ * objagg_destroy - destroys a new objagg instance
+ * @objagg:	objagg instance
+ *
+ * Note: all locking must be provided by the caller.
+ */
+void objagg_destroy(struct objagg *objagg)
+{
+	trace_objagg_destroy(objagg);
+	ida_destroy(&objagg->root_ida);
+	WARN_ON(!list_empty(&objagg->obj_list));
+	rhashtable_destroy(&objagg->obj_ht);
+	if (objagg->hints)
+		objagg_hints_put(objagg->hints);
+	kfree(objagg);
+}
+EXPORT_SYMBOL(objagg_destroy);
+
+static int objagg_stats_info_sort_cmp_func(const void *a, const void *b)
+{
+	const struct objagg_obj_stats_info *stats_info1 = a;
+	const struct objagg_obj_stats_info *stats_info2 = b;
+
+	if (stats_info1->is_root != stats_info2->is_root)
+		return stats_info2->is_root - stats_info1->is_root;
+	if (stats_info1->stats.delta_user_count !=
+	    stats_info2->stats.delta_user_count)
+		return stats_info2->stats.delta_user_count -
+		       stats_info1->stats.delta_user_count;
+	return stats_info2->stats.user_count - stats_info1->stats.user_count;
+}
+
+/**
+ * objagg_stats_get - obtains stats of the objagg instance
+ * @objagg:	objagg instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * The returned structure contains statistics of all object
+ * currently in use, ordered by following rules:
+ * 1) Root objects are always on lower indexes than the rest.
+ * 2) Objects with higher delta user count are always on lower
+ *    indexes.
+ * 3) In case more objects have the same delta user count,
+ *    the objects are ordered by user count.
+ *
+ * Returns a pointer to stats instance in case of success,
+ * otherwise it returns pointer error using ERR_PTR macro.
+ */
+const struct objagg_stats *objagg_stats_get(struct objagg *objagg)
+{
+	struct objagg_stats *objagg_stats;
+	struct objagg_obj *objagg_obj;
+	int i;
+
+	objagg_stats = kzalloc_flex(*objagg_stats, stats_info,
+				    objagg->obj_count);
+	if (!objagg_stats)
+		return ERR_PTR(-ENOMEM);
+
+	i = 0;
+	list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
+		memcpy(&objagg_stats->stats_info[i].stats, &objagg_obj->stats,
+		       sizeof(objagg_stats->stats_info[0].stats));
+		objagg_stats->stats_info[i].objagg_obj = objagg_obj;
+		objagg_stats->stats_info[i].is_root =
+					objagg_obj_is_root(objagg_obj);
+		if (objagg_stats->stats_info[i].is_root)
+			objagg_stats->root_count++;
+		i++;
+	}
+	objagg_stats->stats_info_count = i;
+
+	sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
+	     sizeof(struct objagg_obj_stats_info),
+	     objagg_stats_info_sort_cmp_func, NULL);
+
+	return objagg_stats;
+}
+EXPORT_SYMBOL(objagg_stats_get);
+
+/**
+ * objagg_stats_put - puts stats of the objagg instance
+ * @objagg_stats:	objagg instance stats
+ *
+ * Note: all locking must be provided by the caller.
+ */
+void objagg_stats_put(const struct objagg_stats *objagg_stats)
+{
+	kfree(objagg_stats);
+}
+EXPORT_SYMBOL(objagg_stats_put);
+
+static struct objagg_hints_node *
+objagg_hints_node_create(struct objagg_hints *objagg_hints,
+			 struct objagg_obj *objagg_obj, size_t obj_size,
+			 struct objagg_hints_node *parent_hnode)
+{
+	unsigned int user_count = objagg_obj->stats.user_count;
+	struct objagg_hints_node *hnode;
+	int err;
+
+	hnode = kzalloc(sizeof(*hnode) + obj_size, GFP_KERNEL);
+	if (!hnode)
+		return ERR_PTR(-ENOMEM);
+	memcpy(hnode->obj, &objagg_obj->obj, obj_size);
+	hnode->stats_info.stats.user_count = user_count;
+	hnode->stats_info.stats.delta_user_count = user_count;
+	if (parent_hnode) {
+		parent_hnode->stats_info.stats.delta_user_count += user_count;
+	} else {
+		hnode->root_id = objagg_hints->root_count++;
+		hnode->stats_info.is_root = true;
+	}
+	hnode->stats_info.objagg_obj = objagg_obj;
+
+	err = rhashtable_insert_fast(&objagg_hints->node_ht, &hnode->ht_node,
+				     objagg_hints->ht_params);
+	if (err)
+		goto err_ht_insert;
+
+	list_add(&hnode->list, &objagg_hints->node_list);
+	hnode->parent = parent_hnode;
+	objagg_hints->node_count++;
+
+	return hnode;
+
+err_ht_insert:
+	kfree(hnode);
+	return ERR_PTR(err);
+}
+
+static void objagg_hints_flush(struct objagg_hints *objagg_hints)
+{
+	struct objagg_hints_node *hnode, *tmp;
+
+	list_for_each_entry_safe(hnode, tmp, &objagg_hints->node_list, list) {
+		list_del(&hnode->list);
+		rhashtable_remove_fast(&objagg_hints->node_ht, &hnode->ht_node,
+				       objagg_hints->ht_params);
+		kfree(hnode);
+	}
+}
+
+struct objagg_tmp_node {
+	struct objagg_obj *objagg_obj;
+	bool crossed_out;
+};
+
+struct objagg_tmp_graph {
+	struct objagg_tmp_node *nodes;
+	unsigned long nodes_count;
+	unsigned long *edges;
+};
+
+static int objagg_tmp_graph_edge_index(struct objagg_tmp_graph *graph,
+				       int parent_index, int index)
+{
+	return index * graph->nodes_count + parent_index;
+}
+
+static void objagg_tmp_graph_edge_set(struct objagg_tmp_graph *graph,
+				      int parent_index, int index)
+{
+	int edge_index = objagg_tmp_graph_edge_index(graph, index,
+						     parent_index);
+
+	__set_bit(edge_index, graph->edges);
+}
+
+static bool objagg_tmp_graph_is_edge(struct objagg_tmp_graph *graph,
+				     int parent_index, int index)
+{
+	int edge_index = objagg_tmp_graph_edge_index(graph, index,
+						     parent_index);
+
+	return test_bit(edge_index, graph->edges);
+}
+
+static unsigned int objagg_tmp_graph_node_weight(struct objagg_tmp_graph *graph,
+						 unsigned int index)
+{
+	struct objagg_tmp_node *node = &graph->nodes[index];
+	unsigned int weight = node->objagg_obj->stats.user_count;
+	int j;
+
+	/* Node weight is sum of node users and all other nodes users
+	 * that this node can represent with delta.
+	 */
+
+	for (j = 0; j < graph->nodes_count; j++) {
+		if (!objagg_tmp_graph_is_edge(graph, index, j))
+			continue;
+		node = &graph->nodes[j];
+		if (node->crossed_out)
+			continue;
+		weight += node->objagg_obj->stats.user_count;
+	}
+	return weight;
+}
+
+static int objagg_tmp_graph_node_max_weight(struct objagg_tmp_graph *graph)
+{
+	struct objagg_tmp_node *node;
+	unsigned int max_weight = 0;
+	unsigned int weight;
+	int max_index = -1;
+	int i;
+
+	for (i = 0; i < graph->nodes_count; i++) {
+		node = &graph->nodes[i];
+		if (node->crossed_out)
+			continue;
+		weight = objagg_tmp_graph_node_weight(graph, i);
+		if (weight >= max_weight) {
+			max_weight = weight;
+			max_index = i;
+		}
+	}
+	return max_index;
+}
+
+static struct objagg_tmp_graph *objagg_tmp_graph_create(struct objagg *objagg)
+{
+	unsigned int nodes_count = objagg->obj_count;
+	struct objagg_tmp_graph *graph;
+	struct objagg_tmp_node *node;
+	struct objagg_tmp_node *pnode;
+	struct objagg_obj *objagg_obj;
+	int i, j;
+
+	graph = kzalloc_obj(*graph);
+	if (!graph)
+		return NULL;
+
+	graph->nodes = kzalloc_objs(*graph->nodes, nodes_count);
+	if (!graph->nodes)
+		goto err_nodes_alloc;
+	graph->nodes_count = nodes_count;
+
+	graph->edges = bitmap_zalloc(nodes_count * nodes_count, GFP_KERNEL);
+	if (!graph->edges)
+		goto err_edges_alloc;
+
+	i = 0;
+	list_for_each_entry(objagg_obj, &objagg->obj_list, list) {
+		node = &graph->nodes[i++];
+		node->objagg_obj = objagg_obj;
+	}
+
+	/* Assemble a temporary graph. Insert edge X->Y in case Y can be
+	 * in delta of X.
+	 */
+	for (i = 0; i < nodes_count; i++) {
+		for (j = 0; j < nodes_count; j++) {
+			if (i == j)
+				continue;
+			pnode = &graph->nodes[i];
+			node = &graph->nodes[j];
+			if (objagg->ops->delta_check(objagg->priv,
+						     pnode->objagg_obj->obj,
+						     node->objagg_obj->obj)) {
+				objagg_tmp_graph_edge_set(graph, i, j);
+
+			}
+		}
+	}
+	return graph;
+
+err_edges_alloc:
+	kfree(graph->nodes);
+err_nodes_alloc:
+	kfree(graph);
+	return NULL;
+}
+
+static void objagg_tmp_graph_destroy(struct objagg_tmp_graph *graph)
+{
+	bitmap_free(graph->edges);
+	kfree(graph->nodes);
+	kfree(graph);
+}
+
+static int
+objagg_opt_simple_greedy_fillup_hints(struct objagg_hints *objagg_hints,
+				      struct objagg *objagg)
+{
+	struct objagg_hints_node *hnode, *parent_hnode;
+	struct objagg_tmp_graph *graph;
+	struct objagg_tmp_node *node;
+	int index;
+	int j;
+	int err;
+
+	graph = objagg_tmp_graph_create(objagg);
+	if (!graph)
+		return -ENOMEM;
+
+	/* Find the nodes from the ones that can accommodate most users
+	 * and cross them out of the graph. Save them to the hint list.
+	 */
+	while ((index = objagg_tmp_graph_node_max_weight(graph)) != -1) {
+		node = &graph->nodes[index];
+		node->crossed_out = true;
+		hnode = objagg_hints_node_create(objagg_hints,
+						 node->objagg_obj,
+						 objagg->ops->obj_size,
+						 NULL);
+		if (IS_ERR(hnode)) {
+			err = PTR_ERR(hnode);
+			goto out;
+		}
+		parent_hnode = hnode;
+		for (j = 0; j < graph->nodes_count; j++) {
+			if (!objagg_tmp_graph_is_edge(graph, index, j))
+				continue;
+			node = &graph->nodes[j];
+			if (node->crossed_out)
+				continue;
+			node->crossed_out = true;
+			hnode = objagg_hints_node_create(objagg_hints,
+							 node->objagg_obj,
+							 objagg->ops->obj_size,
+							 parent_hnode);
+			if (IS_ERR(hnode)) {
+				err = PTR_ERR(hnode);
+				goto out;
+			}
+		}
+	}
+
+	err = 0;
+out:
+	objagg_tmp_graph_destroy(graph);
+	return err;
+}
+
+struct objagg_opt_algo {
+	int (*fillup_hints)(struct objagg_hints *objagg_hints,
+			    struct objagg *objagg);
+};
+
+static const struct objagg_opt_algo objagg_opt_simple_greedy = {
+	.fillup_hints = objagg_opt_simple_greedy_fillup_hints,
+};
+
+
+static const struct objagg_opt_algo *objagg_opt_algos[] = {
+	[OBJAGG_OPT_ALGO_SIMPLE_GREEDY] = &objagg_opt_simple_greedy,
+};
+
+/**
+ * objagg_hints_get - obtains hints instance
+ * @objagg:		objagg instance
+ * @opt_algo_type:	type of hints finding algorithm
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * According to the algo type, the existing objects of objagg instance
+ * are going to be went-through to assemble an optimal tree. We call this
+ * tree hints. These hints can be later on used for creation of
+ * a new objagg instance. There, the future object creations are going
+ * to be consulted with these hints in order to find out, where exactly
+ * the new object should be put as a root or delta.
+ *
+ * Returns a pointer to hints instance in case of success,
+ * otherwise it returns pointer error using ERR_PTR macro.
+ */
+struct objagg_hints *objagg_hints_get(struct objagg *objagg,
+				      enum objagg_opt_algo_type opt_algo_type)
+{
+	const struct objagg_opt_algo *algo = objagg_opt_algos[opt_algo_type];
+	struct objagg_hints *objagg_hints;
+	int err;
+
+	objagg_hints = kzalloc_obj(*objagg_hints);
+	if (!objagg_hints)
+		return ERR_PTR(-ENOMEM);
+
+	objagg_hints->ops = objagg->ops;
+	objagg_hints->refcount = 1;
+
+	INIT_LIST_HEAD(&objagg_hints->node_list);
+
+	objagg_hints->ht_params.key_len = objagg->ops->obj_size;
+	objagg_hints->ht_params.key_offset =
+				offsetof(struct objagg_hints_node, obj);
+	objagg_hints->ht_params.head_offset =
+				offsetof(struct objagg_hints_node, ht_node);
+
+	err = rhashtable_init(&objagg_hints->node_ht, &objagg_hints->ht_params);
+	if (err)
+		goto err_rhashtable_init;
+
+	err = algo->fillup_hints(objagg_hints, objagg);
+	if (err)
+		goto err_fillup_hints;
+
+	if (WARN_ON(objagg_hints->node_count != objagg->obj_count)) {
+		err = -EINVAL;
+		goto err_node_count_check;
+	}
+
+	return objagg_hints;
+
+err_node_count_check:
+err_fillup_hints:
+	objagg_hints_flush(objagg_hints);
+	rhashtable_destroy(&objagg_hints->node_ht);
+err_rhashtable_init:
+	kfree(objagg_hints);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(objagg_hints_get);
+
+/**
+ * objagg_hints_put - puts hints instance
+ * @objagg_hints:	objagg hints instance
+ *
+ * Note: all locking must be provided by the caller.
+ */
+void objagg_hints_put(struct objagg_hints *objagg_hints)
+{
+	if (--objagg_hints->refcount)
+		return;
+	objagg_hints_flush(objagg_hints);
+	rhashtable_destroy(&objagg_hints->node_ht);
+	kfree(objagg_hints);
+}
+EXPORT_SYMBOL(objagg_hints_put);
+
+/**
+ * objagg_hints_stats_get - obtains stats of the hints instance
+ * @objagg_hints:	hints instance
+ *
+ * Note: all locking must be provided by the caller.
+ *
+ * The returned structure contains statistics of all objects
+ * currently in use, ordered by following rules:
+ * 1) Root objects are always on lower indexes than the rest.
+ * 2) Objects with higher delta user count are always on lower
+ *    indexes.
+ * 3) In case multiple objects have the same delta user count,
+ *    the objects are ordered by user count.
+ *
+ * Returns a pointer to stats instance in case of success,
+ * otherwise it returns pointer error using ERR_PTR macro.
+ */
+const struct objagg_stats *
+objagg_hints_stats_get(struct objagg_hints *objagg_hints)
+{
+	struct objagg_stats *objagg_stats;
+	struct objagg_hints_node *hnode;
+	int i;
+
+	objagg_stats = kzalloc_flex(*objagg_stats, stats_info,
+				    objagg_hints->node_count);
+	if (!objagg_stats)
+		return ERR_PTR(-ENOMEM);
+
+	i = 0;
+	list_for_each_entry(hnode, &objagg_hints->node_list, list) {
+		memcpy(&objagg_stats->stats_info[i], &hnode->stats_info,
+		       sizeof(objagg_stats->stats_info[0]));
+		if (objagg_stats->stats_info[i].is_root)
+			objagg_stats->root_count++;
+		i++;
+	}
+	objagg_stats->stats_info_count = i;
+
+	sort(objagg_stats->stats_info, objagg_stats->stats_info_count,
+	     sizeof(struct objagg_obj_stats_info),
+	     objagg_stats_info_sort_cmp_func, NULL);
+
+	return objagg_stats;
+}
+EXPORT_SYMBOL(objagg_hints_stats_get);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
+MODULE_DESCRIPTION("Object aggregation manager");