loop: manage partitions in disk image (476a4813) · Commits · 戴 / test

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>

drivers/block/loop.c

+21 −5

Original line number	Diff line number	Diff line
		@@ -82,6 +82,9 @@
		static LIST_HEAD(loop_devices);
		static DEFINE_MUTEX(loop_devices_mutex);

		static int max_part;
		static int part_shift;

		/*
		* Transfer functions
		*/
		@@ -692,6 +695,8 @@ static int loop_change_fd(struct loop_device lo, struct file lo_file,
		goto out_putf;

		fput(old_file);
		if (max_part > 0)
		ioctl_by_bdev(bdev, BLKRRPART, 0);
		return 0;

		out_putf:
		@@ -819,6 +824,8 @@ static int loop_set_fd(struct loop_device lo, struct file lo_file,
		}
		lo->lo_state = Lo_bound;
		wake_up_process(lo->lo_thread);
		if (max_part > 0)
		ioctl_by_bdev(bdev, BLKRRPART, 0);
		return 0;

		out_clr:
		@@ -919,6 +926,8 @@ static int loop_clr_fd(struct loop_device lo, struct block_device bdev)
		fput(filp);
		/* This is safe: open() is still holding a reference. */
		module_put(THIS_MODULE);
		if (max_part > 0)
		ioctl_by_bdev(bdev, BLKRRPART, 0);
		return 0;
		}

		@@ -1360,6 +1369,8 @@ static struct block_device_operations lo_fops = {
		static int max_loop;
		module_param(max_loop, int, 0);
		MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
		module_param(max_part, int, 0);
		MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
		MODULE_LICENSE("GPL");
		MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);

		@@ -1412,7 +1423,7 @@ static struct loop_device *loop_alloc(int i)
		if (!lo->lo_queue)
		goto out_free_dev;

		disk = lo->lo_disk = alloc_disk(1);
		disk = lo->lo_disk = alloc_disk(1 << part_shift);
		if (!disk)
		goto out_free_queue;

		@@ -1422,7 +1433,7 @@ static struct loop_device *loop_alloc(int i)
		init_waitqueue_head(&lo->lo_event);
		spin_lock_init(&lo->lo_lock);
		disk->major = LOOP_MAJOR;
		disk->first_minor = i;
		disk->first_minor = i << part_shift;
		disk->fops = &lo_fops;
		disk->private_data = lo;
		disk->queue = lo->lo_queue;
		@@ -1502,7 +1513,12 @@ static int __init loop_init(void)
		* themselves and have kernel automatically instantiate actual
		* device on-demand.
		*/
		if (max_loop > 1UL << MINORBITS)

		part_shift = 0;
		if (max_part > 0)
		part_shift = fls(max_part);

		if (max_loop > 1UL << (MINORBITS - part_shift))
		return -EINVAL;

		if (max_loop) {
		@@ -1510,7 +1526,7 @@ static int __init loop_init(void)
		range = max_loop;
		} else {
		nr = 8;
		range = 1UL << MINORBITS;
		range = 1UL << (MINORBITS - part_shift);
		}

		if (register_blkdev(LOOP_MAJOR, "loop"))
		@@ -1549,7 +1565,7 @@ static void __exit loop_exit(void)
		unsigned long range;
		struct loop_device lo, next;

		range = max_loop ? max_loop : 1UL << MINORBITS;
		range = max_loop ? max_loop : 1UL << (MINORBITS - part_shift);

		list_for_each_entry_safe(lo, next, &loop_devices, lo_list)
		loop_del_one(lo);

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