770fe30a46
Loop devices today have a fixed pre-allocated number of usually 8.
The number can only be changed at module init time. To find a free
device to use, /dev/loop%i needs to be scanned, and all devices need
to be opened until a free one is possibly found.
This adds a new /dev/loop-control device node, that allows to
dynamically find or allocate a free device, and to add and remove loop
devices from the running system:
LOOP_CTL_ADD adds a specific device. Arg is the number
of the device. It returns the device i or a negative
error code.
LOOP_CTL_REMOVE removes a specific device, Arg is the
number the device. It returns the device i or a negative
error code.
LOOP_CTL_GET_FREE finds the next unbound device or allocates
a new one. No arg is given. It returns the device i or a
negative error code.
The loop kernel module gets automatically loaded when
/dev/loop-control is accessed the first time. The alias
specified in the module, instructs udev to create this
'dead' device node, even when the module is not loaded.
Example:
cfd = open("/dev/loop-control", O_RDWR);
# add a new specific loop device
err = ioctl(cfd, LOOP_CTL_ADD, devnr);
# remove a specific loop device
err = ioctl(cfd, LOOP_CTL_REMOVE, devnr);
# find or allocate a free loop device to use
devnr = ioctl(cfd, LOOP_CTL_GET_FREE);
sprintf(loopname, "/dev/loop%i", devnr);
ffd = open("backing-file", O_RDWR);
lfd = open(loopname, O_RDWR);
err = ioctl(lfd, LOOP_SET_FD, ffd);
Cc: Tejun Heo <tj@kernel.org>
Cc: Karel Zak <kzak@redhat.com>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
167 lines
4.1 KiB
C
167 lines
4.1 KiB
C
#ifndef _LINUX_LOOP_H
|
|
#define _LINUX_LOOP_H
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
|
|
#define LO_NAME_SIZE 64
|
|
#define LO_KEY_SIZE 32
|
|
|
|
#ifdef __KERNEL__
|
|
#include <linux/bio.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/mutex.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];
|
|
uid_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;
|
|
};
|
|
|
|
#endif /* __KERNEL__ */
|
|
|
|
/*
|
|
* Loop flags
|
|
*/
|
|
enum {
|
|
LO_FLAGS_READ_ONLY = 1,
|
|
LO_FLAGS_USE_AOPS = 2,
|
|
LO_FLAGS_AUTOCLEAR = 4,
|
|
};
|
|
|
|
#include <asm/posix_types.h> /* for __kernel_old_dev_t */
|
|
#include <linux/types.h> /* for __u64 */
|
|
|
|
/* Backwards compatibility version */
|
|
struct loop_info {
|
|
int lo_number; /* ioctl r/o */
|
|
__kernel_old_dev_t lo_device; /* ioctl r/o */
|
|
unsigned long lo_inode; /* ioctl r/o */
|
|
__kernel_old_dev_t lo_rdevice; /* ioctl r/o */
|
|
int lo_offset;
|
|
int lo_encrypt_type;
|
|
int lo_encrypt_key_size; /* ioctl w/o */
|
|
int lo_flags; /* ioctl r/o */
|
|
char lo_name[LO_NAME_SIZE];
|
|
unsigned char lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
|
|
unsigned long lo_init[2];
|
|
char reserved[4];
|
|
};
|
|
|
|
struct loop_info64 {
|
|
__u64 lo_device; /* ioctl r/o */
|
|
__u64 lo_inode; /* ioctl r/o */
|
|
__u64 lo_rdevice; /* ioctl r/o */
|
|
__u64 lo_offset;
|
|
__u64 lo_sizelimit;/* bytes, 0 == max available */
|
|
__u32 lo_number; /* ioctl r/o */
|
|
__u32 lo_encrypt_type;
|
|
__u32 lo_encrypt_key_size; /* ioctl w/o */
|
|
__u32 lo_flags; /* ioctl r/o */
|
|
__u8 lo_file_name[LO_NAME_SIZE];
|
|
__u8 lo_crypt_name[LO_NAME_SIZE];
|
|
__u8 lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
|
|
__u64 lo_init[2];
|
|
};
|
|
|
|
/*
|
|
* Loop filter types
|
|
*/
|
|
|
|
#define LO_CRYPT_NONE 0
|
|
#define LO_CRYPT_XOR 1
|
|
#define LO_CRYPT_DES 2
|
|
#define LO_CRYPT_FISH2 3 /* Twofish encryption */
|
|
#define LO_CRYPT_BLOW 4
|
|
#define LO_CRYPT_CAST128 5
|
|
#define LO_CRYPT_IDEA 6
|
|
#define LO_CRYPT_DUMMY 9
|
|
#define LO_CRYPT_SKIPJACK 10
|
|
#define LO_CRYPT_CRYPTOAPI 18
|
|
#define MAX_LO_CRYPT 20
|
|
|
|
#ifdef __KERNEL__
|
|
/* 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
|
|
/*
|
|
* IOCTL commands --- we will commandeer 0x4C ('L')
|
|
*/
|
|
|
|
#define LOOP_SET_FD 0x4C00
|
|
#define LOOP_CLR_FD 0x4C01
|
|
#define LOOP_SET_STATUS 0x4C02
|
|
#define LOOP_GET_STATUS 0x4C03
|
|
#define LOOP_SET_STATUS64 0x4C04
|
|
#define LOOP_GET_STATUS64 0x4C05
|
|
#define LOOP_CHANGE_FD 0x4C06
|
|
#define LOOP_SET_CAPACITY 0x4C07
|
|
|
|
/* /dev/loop-control interface */
|
|
#define LOOP_CTL_ADD 0x4C80
|
|
#define LOOP_CTL_REMOVE 0x4C81
|
|
#define LOOP_CTL_GET_FREE 0x4C82
|
|
#endif
|