linux/drivers/block/loop.h
Pavel Tatashin 6cc8e74308 loop: scale loop device by introducing per device lock
Currently, loop device has only one global lock: loop_ctl_mutex.

This becomes hot in scenarios where many loop devices are used.

Scale it by introducing per-device lock: lo_mutex that protects
modifications of all fields in struct loop_device.

Keep loop_ctl_mutex to protect global data: loop_index_idr, loop_lookup,
loop_add.

The new lock ordering requirement is that loop_ctl_mutex must be taken
before lo_mutex.

Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2021-01-26 13:08:54 -07:00

96 lines
2.3 KiB
C

/*
* 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/blk-mq.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/kthread.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;
atomic_t 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;
void *key_data;
gfp_t old_gfp_mask;
spinlock_t lo_lock;
int lo_state;
struct kthread_worker worker;
struct task_struct *worker_task;
bool use_dio;
bool sysfs_inited;
struct request_queue *lo_queue;
struct blk_mq_tag_set tag_set;
struct gendisk *lo_disk;
struct mutex lo_mutex;
};
struct loop_cmd {
struct kthread_work work;
bool use_aio; /* use AIO interface to handle I/O */
atomic_t ref; /* only for aio */
long ret;
struct kiocb iocb;
struct bio_vec *bvec;
struct cgroup_subsys_state *css;
};
/* 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