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Add priority tagging and buffer reuse for libxfs cache
Merge of master-melb:xfs-cmds:29150a by kenmcd.

  Add priority tagging and buffer reuse for libxfs cache

/*
 * Copyright (c) 2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __LIST_H__
#define __LIST_H__

/*
 * Simple, generic doubly-linked list implementation.
 */

struct list_head {
	struct list_head *next;
	struct list_head *prev;
};

static inline void list_head_init(struct list_head *list)
{
	list->next = list->prev = list;
}

static inline void list_head_destroy(struct list_head *list)
{
	list->next = list->prev = NULL;
}

static inline void __list_add(struct list_head *add,
			      struct list_head *prev, struct list_head *next)
{
	next->prev = add;
	add->next = next;
	add->prev = prev;
	prev->next = add;
}

static inline void list_add(struct list_head *add, struct list_head *head)
{
	__list_add(add, head, head->next);
}

static inline void list_add_tail(struct list_head *add, struct list_head *head)
{
	__list_add(add, head->prev, head);
}

static inline void __list_del(struct list_head *prev, struct list_head *next)
{
	next->prev = prev;
	prev->next = next;
}

static inline void list_del_init(struct list_head *entry)
{
	__list_del(entry->prev, entry->next);
	list_head_init(entry);
}

static inline void list_move(struct list_head *list, struct list_head *head)
{
	__list_del(list->prev, list->next);
	list_add(list, head);
}

static inline void list_move_tail(struct list_head *list, struct list_head *head)
{
	__list_del(list->prev, list->next);
	list_add_tail(list, head);
}

static inline int list_empty(const struct list_head *head)
{
	return head->next == head;
}

static inline void __list_splice(struct list_head *list,
				 struct list_head *head)
{
	struct list_head *first = list->next;
	struct list_head *last = list->prev;
	struct list_head *at = head->next;

	first->prev = head;
	head->next = first;

	last->next = at;
	at->prev = last;
}

static inline void list_splice(struct list_head *list, struct list_head *head)
{
	if (!list_empty(list))
		__list_splice(list, head);
}

static inline void list_splice_init(struct list_head *list,
				    struct list_head *head)
{
	if (!list_empty(list)) {
		__list_splice(list, head);
		list_head_init(list);
	}
}

#define list_entry(ptr, type, member) ({			\
	const typeof( ((type *)0)->member ) *__mptr = (ptr);	\
	(type *)( (char *)__mptr - offsetof(type,member) );})

#define list_for_each(pos, head) \
	for (pos = (head)->next; pos != (head); pos = pos->next)

#define list_for_each_safe(pos, n, head) \
	for (pos = (head)->next, n = pos->next; pos != (head); \
		pos = n, n = pos->next)

#define list_for_each_entry(pos, head, member)				\
	for (pos = list_entry((head)->next, typeof(*pos), member);	\
	     &pos->member != (head); 	\
	     pos = list_entry(pos->member.next, typeof(*pos), member))

#define list_for_each_entry_safe(pos, n, head, member)			\
	for (pos = list_entry((head)->next, typeof(*pos), member),	\
		n = list_entry(pos->member.next, typeof(*pos), member);	\
	     &pos->member != (head); 					\
	     pos = n, n = list_entry(n->member.next, typeof(*n), member))

#endif	/* __LIST_H__ */