MFC: 230000, 230544

MFC: 230000, 230544

Fix a race condition in CAM peripheral free handling, locking
in the CAM XPT bus traversal code, and a number of other periph level
issues.

  r230544 | ken | 2012-01-25 10:58:47 -0700 (Wed, 25 Jan 2012) | 9 lines

  Fix a bug introduced in r230000.  We were eliminating all LUNs on a target
  in response to CAM_DEV_NOT_THERE, instead of just the LUN in question.

  This will now just eliminate the specified LUN in response to
  CAM_DEV_NOT_THERE.

  Reported by:	Richard Todd <rmtodd@servalan.servalan.com>

  r230000 | ken | 2012-01-11 17:41:48 -0700 (Wed, 11 Jan 2012) | 72 lines

  Fix a race condition in CAM peripheral free handling, locking
  in the CAM XPT bus traversal code, and a number of other periph level
  issues.

  cam_periph.h,
  cam_periph.c:	Modify cam_periph_acquire() to test the CAM_PERIPH_INVALID
  		flag prior to allowing a reference count to be gained
  		on a peripheral.  Callers of this function will receive
  		CAM_REQ_CMP_ERR status in the situation of attempting to
  		reference an invalidated periph.  This guarantees that
  		a peripheral scheduled for a deferred free will not
  		be accessed during its wait for destruction.

  		Panic during attempts to drop a reference count on
  		a peripheral that already has a zero reference count.

  		In cam_periph_list(), use a local sbuf with SBUF_FIXEDLEN
  		set so that mallocs do not occur while the xpt topology
  		lock is held, regardless of the allocation policy of the
  		passed in sbuf.

  		Add a new routine, cam_periph_release_locked_buses(),
  		that can be called when the caller already holds
  		the CAM topology lock.

  		Add some extra debugging for duplicate peripheral
  		allocations in cam_periph_alloc().

  		Treat CAM_DEV_NOT_THERE much the same as a selection
  		timeout (AC_LOST_DEVICE is emitted), but forgo retries.

  cam_xpt.c:	Revamp the way the EDT traversal code does locking
  		and reference counting.  This was broken, since it
  		assumed that the EDT would not change during
  		traversal, but that assumption is no longer valid.

  		So, to prevent devices from going away while we
  		traverse the EDT, make sure we properly lock
  		everything and hold references on devices that
  		we are using.

  		The two peripheral driver traversal routines should
  		be examined.  xptpdperiphtraverse() holds the
  		topology lock for the entire time it runs.
  		xptperiphtraverse() is now locked properly, but
  		only holds the topology lock while it is traversing
  		the list, and not while the traversal function is
  		running.

  		The bus locking code in xptbustraverse() should
  		also be revisited at a later time, since it is
  		complex and should probably be simplified.

  scsi_da.c:	Pay attention to the return value from cam_periph_acquire().

  		Return 0 always from daclose() even if the disk is now gone.

  		Add some rudimentary error injection support.

  scsi_sg.c:	Fix reference counting in the sg(4) driver.

  		The sg driver was calling cam_periph_release() on close,
  		but never called cam_periph_acquire() (which increments
  		the reference count) on open.

  		The periph code correctly complained that the sg(4)
  		driver was trying to decrement the refcount when it
  		was already 0.

  Sponsored by:	Spectra Logic

git-svn-id: svn://svn.freebsd.org/base/stable/9@230849 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f