Messages in this thread | | | Subject | Re: [PATCH][v4] Modify loop device to be able to manage partitions of the disk image | From | Laurent Vivier <> | Date | Wed, 19 Mar 2008 21:24:41 +0100 |
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Le mercredi 19 mars 2008 à 13:11 -0700, Randy Dunlap a écrit : > On Wed, 19 Mar 2008 13:36:07 +0100 Laurent Vivier wrote: > > > 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". > > What happened to the update to Documentation/kernel-parameters.txt > that was in v3?
Well, perhaps I didn't understand the comment of Andrew:
"This shouldn't be needed."
I though it means I should remove it. So, Andrew ???
And to comment the changes between v3 and v4:
- remove modification from kernel-parameters.txt (as you saw) - rename the parameter to max_part (according Andrew comments) - add an "ioctl_by_bdev(bdev, BLKRRPART, 0);" on loop_clr_fd() (to remove loopXpY from /dev/ on "losetup -d")
Laurent
> > > 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> > > --- > > drivers/block/loop.c | 26 +++++++++++++++++++++----- > > 1 files changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > > index 91ebb00..f7f1635 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); > > -- > > > --- > ~Randy > -- ------- Laurent.Vivier@bull.net ------- "The best way to predict the future is to invent it." - Alan Kay
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