Doron Shoham schrieb:
> Bastian Blank wrote:
>> On Thu, Sep 04, 2008 at 04:39:24PM +0300, Doron Shoham wrote:
>>> deny allocation of a device which
>>> which mounted on the same device as rootfs.
>>> also deny the allocation of swap devices.
>>> add --allow-mounted flag for overriding this.
>> Neither /etc/mtab nor /dev/mounts provides a proper view on the mounted
>> filesystems. To check the used state you need to try to open it
>> exclusive.
>>
>> Bastian
>>
>
> Can you please explain how to do it?
> What do you mean by "try to open it exclusive"?
This is what I found out.
DRBD[1] uses kernel's bd_claim to see if the device is already claimed.
bd_claim is located in kernel's fs/block_dev.c:
int bd_claim(struct block_device *bdev, void *holder)
{
int res;
spin_lock(&bdev_lock);
/* first decide result */
if (bdev->bd_holder == holder)
res = 0; /* already a holder */
else if (bdev->bd_holder != NULL)
res = -EBUSY; /* held by someone else */
else if (bdev->bd_contains == bdev)
res = 0; /* is a whole device which isn't held */
else if (bdev->bd_contains->bd_holder == bd_claim)
res = 0; /* is a partition of a device that is being partitioned */
else if (bdev->bd_contains->bd_holder != NULL)
res = -EBUSY; /* is a partition of a held device */
else
res = 0; /* is a partition of an un-held device */
How to use it from user-space? Any kernel hackers out there? ;)
[1] http://www.drbd.org
--
Tomasz Chmielewski
http://wpkg.org
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