Messages in this thread | | | From | Albert Cahalan <> | Subject | Re: ext2 in a dos file/partition | Date | Tue, 12 Mar 1996 01:10:19 -0500 (EST) |
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> You could do this, with the loop device, but you'd have to write some > support programs. What you'd do is given a host file, make sure it's > contiguous, and find its start block, using the appropriate ioctl's. > (See how LILO determines the blocks used for the kernel image file for > an example.) Then open the device (/dev/hda1, or whatever), and set up > the loop device to use that device, with the specified starting offset > for the vbd start.
> point is that the loop device can either create a virtual block device > based on a device OR a file. As you point out, a possible application > of basing a vbd on top of a device is to handle wierd partitions in user > mode. Just read in the BSD disklabel, and then set up the loop device > with the correct starting offset. > > In order to completely use the loop device for this applicaiton, we > would need to have a method of manually setting the size of the > partition of the virtual device. Right now, the size is set to the size > of the parent device or file minus the starting offset. We need to > create a new ioctl to restrict the size down to the size specified in > the non-native partition table. This wouldn't be at all difficult,
This would be _great_ for all the people sharing swap between Linux and Windows. There could be a winswapon command that adds the swap signiture a few blocks into the file, looks up the block and verifies that the file really is contiguous, attaches a loopback device to the disk at the proper offset, and then enables swapping. Putting this into one command would make swap sharing really easy, yet fast.
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