the default. Most servers just shovel bits from their backend to
the kernel without checking the contents and dumping core in case
the backend gives garbage is a bit harsh.
Note: We use the storage of puffs_cache_write from puffs_ops for
this purpose. It's not issued by the kernel and hence currently
unused, and this saves us from the trouble of bumping the lib major
version.
and before puffs_mount().
(this should actually be integrated with puffs_exit(), but that
routine is currently so non-sensible that I didn't bother now)
Previously each request was executed on its own callcontext and
switched to every time the request was being processed. Now requests
borrow the mainloop context and switch only if/when they yield.
This takes two context switches away from a file system request
bringing down the typical amounts 2->0 (e.g. dtfs) and 4->2 (e.g.
psshfs).
The interfaces for manually executing requests changed a bit:
puffs_dispatch_create() and puffs_dispatch_exec() must now be used.
They are not tested, as nothing in-tree wants them and I doubt
anyone else is really interested in them either.
Also do some misc code cleanup related to execution contexts. The
"work-in-progress checkpoint" committed over a year ago was starting
to look slightly weed-infested.
them every time. Speeds up pure in-memory file systems such as
sysctlfs or dtfs quite a bit. For actual I/O-workhorses the result
is of course less tasty.
If the env variable PUFFS_COMFD is set, the descriptor value
contained in it is used for communication instead of opening
/dev/puffs and doing mount(2).
This feature is obviously very undocumented and should not be used
without adult supervision.
Get rid of the original puffs_req(3) framework and use puffs_framebuf(3)
instead for file system requests. It has the advantage of being
suitable for transporting a distributed message passing protocol
and therefore us being able to run the file system server on any
host.
Ok, puffs is not quite here yet: libpuffs needs to grow request
routing support and the message contents need to be munged into a
host independent format. Saying which format would be telling,
but it might begin with an X, end in an L and have the 13th character
in the middle. Keep an eye out for the sequels: Parts 3+m/n.
separately
* provide puffs_cc_getcc()
This is in preparation for the removal of you-should-guess-what as
an argument to routines here and there and everywhere.
also synchronizes with puffs_mount() and does not return (exit) in the
parent process until the file system has been mounted. This makes
it possible to reliably run e.g. mount_foo jippi /kai ; cd /kai/ee
servers. Calling daemon() (i.e. fork()ing) inside a library can
cause nice surprises for e.g. threaded programs. As discussed with
Greg Oster & others.
alternative to the (vastly superior ;) continuation model. This
is very preliminary stuff and not compiled by default (which it
even won't do without some other patches I cannot commit yet).
The raison d'commit of the patch is a snippet which ensures proper
in-order dispatching of all operations, including those which don't
require a response. Previously many of them would be dispatched
simultaneosly, e.g. fsync and reclaim on the same node, which
obviously isn't all that nice for correct operation.
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