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authorLaurent Vivier <Laurent.Vivier@bull.net>2008-03-26 12:11:53 +0100
committerJens Axboe <jens.axboe@oracle.com>2008-04-21 09:50:08 +0200
commit476a4813cfddf7cf159956cc0e2d3c830c1507e3 (patch)
tree11c824363b8ea789ccb3c6f3b38320bcf79b3aa4
parent22a9189fd073db3d03a4cf8b8c098aa207602de1 (diff)
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>
-rw-r--r--drivers/block/loop.c26
1 files changed, 21 insertions, 5 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 91ebb007416c..f7f163557aa0 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -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);