linux-imx

/*

 * Copyright (C) 2009-2011 Red Hat, Inc.

 *

 * Author: Mikulas Patocka <mpatocka@redhat.com>

 *

 * This file is released under the GPL.

 */

​

#include <linux/dm-bufio.h>

​

#include <linux/device-mapper.h>

#include <linux/dm-io.h>

#include <linux/slab.h>

#include <linux/sched/mm.h>

#include <linux/jiffies.h>

#include <linux/vmalloc.h>

#include <linux/shrinker.h>

#include <linux/module.h>

#include <linux/rbtree.h>

#include <linux/stacktrace.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    30

​

/*

 * Free buffers when they are older than this (seconds)

 */

#define DM_BUFIO_DEFAULT_AGE_SECS   300

​

/*

 * The nr of bytes of cached data to keep around.

 */

#define DM_BUFIO_DEFAULT_RETAIN_BYTES   (256 * 1024)

​

/*

 * Align buffer writes to this boundary.

 * Tests show that SSDs have the highest IOPS when using 4k writes.

 */

#define DM_BUFIO_WRITE_ALIGN        4096

​

/*

 * dm_buffer->list_mode

 */

#define LIST_CLEAN  0

#define LIST_DIRTY  1

#define LIST_SIZE   2

​

/*

 * Linking of buffers:

 *  All buffers are linked to cache_hash with their hash_list field.

 *

 *  Clean buffers that are not being written (B_WRITING not set)

 *  are linked to lru[LIST_CLEAN] with their lru_list field.

 *

 *  Dirty and clean buffers that are being written are linked to

 *  lru[LIST_DIRTY] with their lru_list field. When the write

 *  finishes, the buffer cannot be relinked immediately (because we

 *  are in an interrupt context and relinking requires process

 *  context), so some clean-not-writing buffers can be held on

 *  dirty_lru too.  They are later added to lru in the process

 *  context.

 */

struct dm_bufio_client {

    struct mutex lock;

​

    struct list_head lru[LIST_SIZE];

    unsigned long n_buffers[LIST_SIZE];

​

    struct block_device *bdev;

    unsigned block_size;

    s8 sectors_per_block_bits;

    void (*alloc_callback)(struct dm_buffer *);

    void (*write_callback)(struct dm_buffer *);

​