loop.h

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/*
 * include/linux/loop.h
 *
 * Written by Theodore Ts'o, 3/29/93.
 *
 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
 * permitted under the GNU General Public License.
 */
#ifndef _LINUX_LOOP_H
#define _LINUX_LOOP_H

#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <uapi/linux/loop.h>

/* Possible states of device */
enum {
    Lo_unbound,
    Lo_bound,
    Lo_rundown,
};

struct loop_func_table;

struct loop_device {
    int     lo_number;
    int     lo_refcnt;
    loff_t      lo_offset;
    loff_t      lo_sizelimit;
    int     lo_flags;
    int     (*transfer)(struct loop_device *, int cmd,
                    struct page *raw_page, unsigned raw_off,
                    struct page *loop_page, unsigned loop_off,
                    int size, sector_t real_block);
    char        lo_file_name[LO_NAME_SIZE];
    char        lo_crypt_name[LO_NAME_SIZE];
    char        lo_encrypt_key[LO_KEY_SIZE];
    int     lo_encrypt_key_size;
    struct loop_func_table *lo_encryption;
    __u32           lo_init[2];
    kuid_t      lo_key_owner;   /* Who set the key */
    int     (*ioctl)(struct loop_device *, int cmd, 
                 unsigned long arg); 

    struct file *   lo_backing_file;
    struct block_device *lo_device;
    unsigned    lo_blocksize;
    void        *key_data; 

    gfp_t       old_gfp_mask;

    spinlock_t      lo_lock;
    struct bio_list     lo_bio_list;
    int         lo_state;
    struct mutex        lo_ctl_mutex;
    struct task_struct  *lo_thread;
    wait_queue_head_t   lo_event;

    struct request_queue    *lo_queue;
    struct gendisk      *lo_disk;
};

/* Support for loadable transfer modules */
struct loop_func_table {
    int number; /* filter type */ 
    int (*transfer)(struct loop_device *lo, int cmd,
            struct page *raw_page, unsigned raw_off,
            struct page *loop_page, unsigned loop_off,
            int size, sector_t real_block);
    int (*init)(struct loop_device *, const struct loop_info64 *); 
    /* release is called from loop_unregister_transfer or clr_fd */
    int (*release)(struct loop_device *); 
    int (*ioctl)(struct loop_device *, int cmd, unsigned long arg);
    struct module *owner;
}; 

int loop_register_transfer(struct loop_func_table *funcs);
int loop_unregister_transfer(int number); 

#endif