userspace, since it doesn't contain any information yet. I should
still rework this more so this is just a quickie to get the read/write
style interface more up to speed with the ioctl version.
interacts with the userspace file server:
* since the kernel-user communication is not purely request-response
anymore (hasn't been since 2006), try to rename some "request" to
"message". more similar mangling will take place in the future.
* completely rework how messages are allocated. previously most of
them were borrowed from the stack (originally *all* of them),
but now always allocate dynamically. this makes the structure
of the code much cleaner. also makes it possible to fix a
locking order violation. it enables plenty of future enhancements.
* start generalizing the transport interface to be independent of puffs
* move transport interface to read/write instead of ioctl. the
old one had legacy design problems, and besides, ioctl's suck.
implement a very generic version for now; this will be
worked on later hopefully some day reaching "highly optimized".
* implement libpuffs support behind existing library request
interfaces. this will change eventually (I hate those interfaces)
kernel to the file server for silly things the file server did,
e.g. attempting to create a file with size VSIZENOTSET. The file
server can handle these as it chooses, but the default action is
for it to throw its hands in the air and sing "goodbye, cruel world,
it's over, walk on by".
the maximum request size after mount. Calling mount(MNT_GETARGS)
from the file server is currently not kosher, as it vrele()s the
root vnode, potentially causing an inactive, which the file server
cannot handle while it itself is inactive in the kernel (deadlock).
Add an additional call with MNT_GETARGS to retrieve the modified
information instead of relying on the kernel code abusing the mount
interface during mount.
* in addition add/remove, allow enable/disable, which can be used
to control events for descriptors without having to remove all the
data associated with them
* add directsend/receive, which can be used to pass the same buffer
from the caller to read/writeframe and back again
* add flags to enqueue functions and allow urgent buffers to be
processed as the next PDU
pooka