linux-imx

/*

 * Ram backed block device driver.

 *

 * Copyright (C) 2007 Nick Piggin

 * Copyright (C) 2007 Novell Inc.

 *

 * Parts derived from drivers/block/rd.c, and drivers/block/loop.c, copyright

 * of their respective owners.

 */

​

#include <linux/init.h>

#include <linux/initrd.h>

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/major.h>

#include <linux/blkdev.h>

#include <linux/bio.h>

#include <linux/highmem.h>

#include <linux/mutex.h>

#include <linux/radix-tree.h>

#include <linux/fs.h>

#include <linux/slab.h>

#include <linux/backing-dev.h>

​

#include <linux/uaccess.h>

​

#define PAGE_SECTORS_SHIFT  (PAGE_SHIFT - SECTOR_SHIFT)

#define PAGE_SECTORS        (1 << PAGE_SECTORS_SHIFT)

​

/*

 * Each block ramdisk device has a radix_tree brd_pages of pages that stores

 * the pages containing the block device's contents. A brd page's ->index is

 * its offset in PAGE_SIZE units. This is similar to, but in no way connected

 * with, the kernel's pagecache or buffer cache (which sit above our block

 * device).

 */

struct brd_device {

    int     brd_number;

​

    struct request_queue    *brd_queue;

    struct gendisk      *brd_disk;

    struct list_head    brd_list;

​

    /*

     * Backing store of pages and lock to protect it. This is the contents

     * of the block device.

     */

    spinlock_t      brd_lock;

    struct radix_tree_root  brd_pages;

};

​

/*

 * Look up and return a brd's page for a given sector.

 */

static struct page *brd_lookup_page(struct brd_device *brd, sector_t sector)

{

    pgoff_t idx;

    struct page *page;

​

    /*

     * The page lifetime is protected by the fact that we have opened the

     * device node -- brd pages will never be deleted under us, so we

     * don't need any further locking or refcounting.