From: Dexuan Cui <decui@microsoft.com> Sent: Saturday, January 25, 2020 11:54 AM

Add util_pre_suspend() and util_pre_resume() for some hv_utils devices
(e.g. kvp/vss/fcopy), because they need special handling before
util_suspend() calls vmbus_close().

For kvp, all the possible pending work items should be cancelled.

For vss and fcopy, some extra clean-up needs to be done, i.e. fake a
THAW message for hv_vss_daemon and fake a CANCEL_FCOPY message for
hv_fcopy_daemon, otherwise when the VM resums back, the daemons
can end up in an inconsistent state (i.e. the file systems are
frozen but will never be thawed; the file transmitted via fcopy
may not be complete). Note: there is an extra patch for the daemons:
"Tools: hv: Reopen the devices if read() or write() returns errors",
because the hv_utils driver can not guarantee the whole transaction
finishes completely once util_suspend() starts to run (at this time,
all the userspace processes are frozen).

util_probe() disables channel->callback_event to avoid the race with
the channel callback.

Signed-off-by: Dexuan Cui <decui@microsoft.com>

---
Changes in v2:
    Handles fcopy/vss specially to avoid possible inconsistent states.

Changes in v3 (I addressed Michael's comments):
    Removed unneeded blank lines.
    Simplified the error handling logic by allocating memory earlier.
    Added a comment before util_suspend(): when we're in the function,
      all the userspace processes have been frozen.

 drivers/hv/hv_fcopy.c     | 54 +++++++++++++++++++++++++++++++++-
 drivers/hv/hv_kvp.c       | 43 +++++++++++++++++++++++++--
 drivers/hv/hv_snapshot.c  | 55 ++++++++++++++++++++++++++++++++--
 drivers/hv/hv_util.c      | 62 ++++++++++++++++++++++++++++++++++++++-
 drivers/hv/hyperv_vmbus.h |  6 ++++
 include/linux/hyperv.h    |  2 ++
 6 files changed, 216 insertions(+), 6 deletions(-)

Reviewed-by: Michael Kelley <redacted>