On Thu, 15 Aug 1996, Allen Briggs wrote:

On ????, Henry B. Hotz wrote:
> > I would love to be able to re-use my MacOS Swap partition (which is full of
> > a single VM file) as a BSD swap partition.

My thoughts exactly.

> This would be cool, and might be theoretically possible if that file is
> one unbroken range of blocks.  The challenge is then describing that
> swap space to the kernel.  Currently, the kernel expects swap to take
> up an entire device...  Hmmm...  I think that gives us a couple of
> options...


What about an hfsswap driver that stores a mapping table (preferrably in
memory with disk backup and multiple redundancies with error checking) and
remaps the blocks of an hfs file into a "pseudo" device, so that the
regular swap code handles it in the same way as a _real_ swap
partition on the root device.  It would have to basically serve as a
front-end to the scsi code, possibly as part of the scsi code, to work in
that manner.  That's the disadvantage.  The advantage is that nobody would
have to mess with the swap code.  The other advantage is that you could
conceivably put the swap file on any partition without compiling a custom
kernel or using one somebody else has compiled.

Another possibility would, of course, be to add support for that to the
swap code... a very drastic undertaking, and less useful, as noted below.

On a similar note, if the code already existed within the kernel for
remapping HFS blocks to devices, it could also be used to implement pseudo
filesystems on a Mac volume.  Possible benefits to making this possible
include the ability to copy a Mac-side NetBSD filesystem to another drive
by clicking and dragging, the ability to install NetBSD without even
_creating_ partitions....  Granted, it wouldn't be quite as fast as a
native partition, but it would probably be very beneficial for people who
are messing with MacMint and MacMinix who would like to move to NetBSD but
are hesitant to commit their hard drive to it.  The installation procedure
could be simple, too.  Basically, the first-time-user distribution could
consist of a small partition with all the files already installed, and, if
possible, a (MacOS) program to alter the size of the MacOS-side partition.

There are problems with that, not the least of which are finding a way to
create the filesystem in the first place (mkfs equivalent) and getting the
installer to recognize it, but as a long term goal, it might be nice.

Thoughts?

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