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nbd: adjust 'max_part' according to part_shift

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The 'max_part' parameter determines how many partitions are supported
on each nbd device. However the actual number can be changed to the
power of 2 minus 1 form during the module initialization as
alloc_disk() is called with (1 << part_shift) for some reason.

So adjust 'max_part' also at least for consistency with loop and brd.
It is exported via sysfs already, and a user should check this value
after module loading if [s]he wants to use that number correctly
(i.e. fdisk or something).

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Laurent Vivier <Laurent.Vivier@bull.net>
Cc: Paul Clements <Paul.Clements@steeleye.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Namhyung Kim 2011-05-28 14:44:46 +02:00 committed by Jens Axboe
parent 3b2710824e
commit 5988ce2396
1 changed files with 12 additions and 1 deletions
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13
drivers/block/nbd.c
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@ -754,9 +754,20 @@ static int __init nbd_init(void)
return -ENOMEM; return -ENOMEM;
part_shift = 0; part_shift = 0;
if (max_part > 0) if (max_part > 0) {
part_shift = fls(max_part); part_shift = fls(max_part);
/*
* Adjust max_part according to part_shift as it is exported
* to user space so that user can know the max number of
* partition kernel should be able to manage.
*
* Note that -1 is required because partition 0 is reserved
* for the whole disk.
*/
max_part = (1UL << part_shift) - 1;
}
if ((1UL << part_shift) > DISK_MAX_PARTS) if ((1UL << part_shift) > DISK_MAX_PARTS)
return -EINVAL; return -EINVAL;