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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