FreeBSD's front and back Xen blkif interface drivers.
sys/dev/xen/blkfront/block.h:
sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkback/blkback.c:
Replace FreeBSD specific multi-page ring impelementation with
support for both the Citrix and Amazon/RedHat versions of this
extension.
sys/dev/xen/blkfront/blkfront.c:
o Add a per-instance sysctl tree that exposes all negotiated
transport parameters (ring pages, max number of requests,
max request size, max number of segments).
o In blkfront_vdevice_to_unit() add a missing return statement
so that we properly identify the unit number for high numbered
xvd devices.
sys/dev/xen/blkback/blkback.c:
o Add static dtrace probes for several events in this driver.
o Defer connection shutdown processing until the front-end
enters the closed state. This avoids prematurely tearing
down the connection when buggy front-ends transition to the
closing state, even though the device is open and they
veto the close request from the tool stack.
o Add nodes for maximum request size and the number of active
ring pages to the exising, per-instance, sysctl tree.
o Miscelaneous style cleanup.
sys/xen/interface/io/blkif.h:
o Add extensive documentation of the XenStore nodes used to
implement the blkif interface.
o Document the startup sequence between a front and back driver.
o Add structures and documenatation for the "discard" feature
(AKA Trim).
o Cleanup some definitions related to FreeBSD's request
number/size/segment-limit extension.
sys/dev/xen/blkfront/blkfront.c:
sys/dev/xen/blkback/blkback.c:
sys/xen/xenbus/xenbusvar.h:
Add the convenience function xenbus_get_otherend_state() and
use it to simplify some logic in both block-front and block-back.
MFC after: 1 day
8b8bfa3567