Fix a race with the vnode reclamation in the aio_qphysio().  Obtain the thread reference on the vp->v_rdev and use the returned struct cdev *dev instead of using vp->v_rdev.  Call dev_strategy_csw() instead of dev_strategy(), since we now own the reference.
Fix a race with the vnode reclamation in the aio_qphysio().  Obtain
the thread reference on the vp->v_rdev and use the returned struct
cdev *dev instead of using vp->v_rdev.  Call dev_strategy_csw()
instead of dev_strategy(), since we now own the reference.

Since the csw was already calculated, test d_flags to avoid mapping
the buffer if the driver supports unmapped requests [*].

Suggested by:	kan [*]
Reviewed by:	kan (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase