The patch titled
loop: modify loop device to be able to manage partitions of the disk image
has been added to the -mm tree. Its filename is
loop-modify-loop-device-to-be-able-to-manage-partitions-of-the-disk-image.patch
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------------------------------------------------------
Subject: loop: modify loop device to be able to manage partitions of the disk image
From: Laurent Vivier <Laurent.Vivier@xxxxxxxx>
This patch allows to use loop device with partitioned 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@xxxxxxxx>
Cc: Jens Axboe <jens.axboe@xxxxxxxxxx>
Cc: Andries Brouwer <Andries.Brouwer@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/loop.c | 26 +++++++++++++++++++++-----
1 file changed, 21 insertions(+), 5 deletions(-)
diff -puN drivers/block/loop.c~loop-modify-loop-device-to-be-able-to-manage-partitions-of-the-disk-image drivers/block/loop.c
--- a/drivers/block/loop.c~loop-modify-loop-device-to-be-able-to-manage-partitions-of-the-disk-image
+++ a/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_de
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_devic
}
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_devic
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
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(in
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(in
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);
_
Patches currently in -mm which might be from Laurent.Vivier@xxxxxxxx are
git-kvm.patch
nbd-allow-nbd-to-be-used-locally.patch
loop-modify-loop-device-to-be-able-to-manage-partitions-of-the-disk-image.patch
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