From 476a4813cfddf7cf159956cc0e2d3c830c1507e3 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Wed, 26 Mar 2008 12:11:53 +0100 Subject: [PATCH] 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 Signed-off-by: Jens Axboe --- drivers/block/loop.c | 26 +++++++++++++++++++++----- 1 file changed, 21 insertions(+), 5 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 91ebb00741..f7f163557a 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); -- 2.39.5