forked from luck/tmp_suning_uos_patched
f893366795
The lo_ctl_mutex is held for running all ioctl handlers, and in some ioctl handlers, ioctl_by_bdev(BLKRRPART) is called for rereading partitions, which requires bd_mutex. So it is easy to cause failure because trylock(bd_mutex) may fail inside blkdev_reread_part(), and follows the lock context: blkid or other application: ->open() ->mutex_lock(bd_mutex) ->lo_open() ->mutex_lock(lo_ctl_mutex) losetup(set fd ioctl): ->mutex_lock(lo_ctl_mutex) ->ioctl_by_bdev(BLKRRPART) ->trylock(bd_mutex) This patch trys to eliminate the ABBA lock dependency by removing lo_ctl_mutext in lo_open() with the following approach: 1) make lo_refcnt as atomic_t and avoid acquiring lo_ctl_mutex in lo_open(): - for open vs. add/del loop, no any problem because of loop_index_mutex - freeze request queue during clr_fd, so I/O can't come until clearing fd is completed, like the effect of holding lo_ctl_mutex in lo_open - both open() and release() have been serialized by bd_mutex already 2) don't hold lo_ctl_mutex for decreasing/checking lo_refcnt in lo_release(), then lo_ctl_mutex is only required for the last release. Reviewed-by: Christoph Hellwig <hch@lst.de> Tested-by: Jarod Wilson <jarod@redhat.com> Acked-by: Jarod Wilson <jarod@redhat.com> Signed-off-by: Ming Lei <ming.lei@canonical.com> Signed-off-by: Jens Axboe <axboe@fb.com>
93 lines
2.3 KiB
C
93 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/workqueue.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;
|
|
unsigned lo_blocksize;
|
|
void *key_data;
|
|
|
|
gfp_t old_gfp_mask;
|
|
|
|
spinlock_t lo_lock;
|
|
struct workqueue_struct *wq;
|
|
struct list_head write_cmd_head;
|
|
struct work_struct write_work;
|
|
bool write_started;
|
|
int lo_state;
|
|
struct mutex lo_ctl_mutex;
|
|
|
|
struct request_queue *lo_queue;
|
|
struct blk_mq_tag_set tag_set;
|
|
struct gendisk *lo_disk;
|
|
};
|
|
|
|
struct loop_cmd {
|
|
struct work_struct read_work;
|
|
struct request *rq;
|
|
struct list_head list;
|
|
};
|
|
|
|
/* 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
|