path: root/drivers/md/dm-bufio.c

/*
 * Copyright (C) 2009-2011 Red Hat, Inc.
 *
 * Author: Mikulas Patocka <mpatocka@redhat.com>
 *
 * This file is released under the GPL.
 */

#include "dm-bufio.h"

#include <linux/device-mapper.h>
#include <linux/dm-io.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/shrinker.h>
#include <linux/module.h>

#define DM_MSG_PREFIX "bufio"

/*
 * Memory management policy:
 *	Limit the number of buffers to DM_BUFIO_MEMORY_PERCENT of main memory
 *	or DM_BUFIO_VMALLOC_PERCENT of vmalloc memory (whichever is lower).
 *	Always allocate at least DM_BUFIO_MIN_BUFFERS buffers.
 *	Start background writeback when there are DM_BUFIO_WRITEBACK_PERCENT
 *	dirty buffers.
 */
#define DM_BUFIO_MIN_BUFFERS		8

#define DM_BUFIO_MEMORY_PERCENT		2
#define DM_BUFIO_VMALLOC_PERCENT	25
#define DM_BUFIO_WRITEBACK_PERCENT	75

/*
 * Check buffer ages in this interval (seconds)
 */
#define DM_BUFIO_WORK_TIMER_SECS	10

/*
 * Free buffers when they are older than this (seconds)
 */
#define DM_BUFIO_DEFAULT_AGE_SECS	60

/*
 * The number of bvec entries that are embedded directly in the buffer.
 * If the chunk size is larger, dm-io is used to do the io.
 */
#define DM_BUFIO_INLINE_VECS		16

/*
 * Buffer hash
 */
#define DM_BUFIO_HASH_BITS	20
#define DM_BUFIO_HASH(block) \
	((((block) >> DM_BUFIO_HASH_BITS) ^ (block)) & \
	 ((1 <<