loop: manage partitions in disk image
This patch allows to use loop device with partitionned disk image. Original behavior of loop is not modified. A new parameter is introduced to define how many partition we want to be able to manage per loop device. This parameter is "max_part". For instance, to manage 63 partitions / loop device, we will do: # modprobe loop max_part=63 # ls -l /dev/loop?* brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0 brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1 brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2 brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3 brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4 brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5 brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6 brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7 And to attach a raw partitionned disk image, the original losetup is used: # losetup -f etch.img # ls -l /dev/loop?* brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0 brw-rw---- 1 root disk 7, 1 2008-03-05 14:57 /dev/loop0p1 brw-rw---- 1 root disk 7, 2 2008-03-05 14:57 /dev/loop0p2 brw-rw---- 1 root disk 7, 5 2008-03-05 14:57 /dev/loop0p5 brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1 brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2 brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3 brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4 brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5 brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6 brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7 # mount /dev/loop0p1 /mnt # ls /mnt bench cdrom home lib mnt root srv usr bin dev initrd lost+found opt sbin sys var boot etc initrd.img media proc selinux tmp vmlinuz # umount /mnt # losetup -d /dev/loop0 Of course, the same behavior can be done using kpartx on a loop device, but modifying loop avoids to stack several layers of block device (loop + device mapper), this is a very light modification (40% of modifications are to manage the new parameter). Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
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22a9189fd0
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476a4813cf
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@ -82,6 +82,9 @@
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static LIST_HEAD(loop_devices);
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static LIST_HEAD(loop_devices);
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static DEFINE_MUTEX(loop_devices_mutex);
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static DEFINE_MUTEX(loop_devices_mutex);
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static int max_part;
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static int part_shift;
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/*
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/*
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* Transfer functions
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* Transfer functions
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*/
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*/
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@ -692,6 +695,8 @@ static int loop_change_fd(struct loop_device *lo, struct file *lo_file,
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goto out_putf;
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goto out_putf;
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fput(old_file);
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fput(old_file);
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if (max_part > 0)
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ioctl_by_bdev(bdev, BLKRRPART, 0);
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return 0;
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return 0;
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out_putf:
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out_putf:
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@ -819,6 +824,8 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
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}
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}
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lo->lo_state = Lo_bound;
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lo->lo_state = Lo_bound;
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wake_up_process(lo->lo_thread);
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wake_up_process(lo->lo_thread);
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if (max_part > 0)
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ioctl_by_bdev(bdev, BLKRRPART, 0);
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return 0;
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return 0;
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out_clr:
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out_clr:
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@ -919,6 +926,8 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
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fput(filp);
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fput(filp);
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/* This is safe: open() is still holding a reference. */
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/* This is safe: open() is still holding a reference. */
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module_put(THIS_MODULE);
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module_put(THIS_MODULE);
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if (max_part > 0)
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ioctl_by_bdev(bdev, BLKRRPART, 0);
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return 0;
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return 0;
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}
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}
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@ -1360,6 +1369,8 @@ static struct block_device_operations lo_fops = {
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static int max_loop;
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static int max_loop;
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module_param(max_loop, int, 0);
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module_param(max_loop, int, 0);
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MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
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MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
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module_param(max_part, int, 0);
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MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
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MODULE_LICENSE("GPL");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
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MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
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@ -1412,7 +1423,7 @@ static struct loop_device *loop_alloc(int i)
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if (!lo->lo_queue)
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if (!lo->lo_queue)
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goto out_free_dev;
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goto out_free_dev;
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disk = lo->lo_disk = alloc_disk(1);
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disk = lo->lo_disk = alloc_disk(1 << part_shift);
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if (!disk)
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if (!disk)
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goto out_free_queue;
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goto out_free_queue;
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@ -1422,7 +1433,7 @@ static struct loop_device *loop_alloc(int i)
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init_waitqueue_head(&lo->lo_event);
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init_waitqueue_head(&lo->lo_event);
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spin_lock_init(&lo->lo_lock);
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spin_lock_init(&lo->lo_lock);
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disk->major = LOOP_MAJOR;
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disk->major = LOOP_MAJOR;
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disk->first_minor = i;
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disk->first_minor = i << part_shift;
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disk->fops = &lo_fops;
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disk->fops = &lo_fops;
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disk->private_data = lo;
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disk->private_data = lo;
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disk->queue = lo->lo_queue;
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disk->queue = lo->lo_queue;
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@ -1502,7 +1513,12 @@ static int __init loop_init(void)
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* themselves and have kernel automatically instantiate actual
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* themselves and have kernel automatically instantiate actual
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* device on-demand.
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* device on-demand.
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*/
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*/
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if (max_loop > 1UL << MINORBITS)
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part_shift = 0;
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if (max_part > 0)
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part_shift = fls(max_part);
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if (max_loop > 1UL << (MINORBITS - part_shift))
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return -EINVAL;
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return -EINVAL;
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if (max_loop) {
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if (max_loop) {
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@ -1510,7 +1526,7 @@ static int __init loop_init(void)
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range = max_loop;
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range = max_loop;
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} else {
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} else {
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nr = 8;
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nr = 8;
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range = 1UL << MINORBITS;
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range = 1UL << (MINORBITS - part_shift);
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}
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}
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if (register_blkdev(LOOP_MAJOR, "loop"))
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if (register_blkdev(LOOP_MAJOR, "loop"))
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@ -1549,7 +1565,7 @@ static void __exit loop_exit(void)
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unsigned long range;
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unsigned long range;
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struct loop_device *lo, *next;
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struct loop_device *lo, *next;
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range = max_loop ? max_loop : 1UL << MINORBITS;
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range = max_loop ? max_loop : 1UL << (MINORBITS - part_shift);
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list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
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list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
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loop_del_one(lo);
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loop_del_one(lo);
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