VSS stands for "Volume Shadow Copy Service". Unlike virtual machine
snapshot, it only takes snapshot for the virtual disks, so both
filesystem and applications have to aware of it, and cooperate the
whole VSS process.
This driver exposes two device files to the userland:
/dev/hv_fsvss_dev
Normally userland programs should _not_ mess with this device file.
It is currently used by the hv_vss_daemon(8), which freezes and
thaws the filesystem. NOTE: currently only UFS is supported, if
the system mounts _any_ other filesystems, the hv_vss_daemon(8)
will veto the VSS process.
If hv_vss_daemon(8) was disabled, then this device file must be
opened, and proper ioctls must be issued to keep the VSS working.
/dev/hv_appvss_dev
Userland application can opened this device file to receive the
VSS freeze notification, hold the VSS for a while (mainly to flush
application data to filesystem), release the VSS process, and
receive the VSS thaw notification i.e. applications can run again.
The VSS will still work, even if this device file is not opened.
However, only filesystem consistency is promised, if this device
file is not opened or is not operated properly.
hv_vss_daemon(8) is started by devd(8) by default. It can be disabled
by editting /etc/devd/hyperv.conf.
Submitted by: Hongjiang Zhang <honzhan microsoft com>
Reviewed by: kib, mckusick
MFC after: 3 weeks
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D8224
While I'm here, move message status codes to hv_utilreg.h, since they
will be used by the upcoming VSS stuffs.
Submitted by: Hongjiang Zhang <honzhan microsoft com>
MFC after: 1 week
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D8391
Submitted by: Jun Su <junsu microsoft com>
Reviewed by: Dexuan Cui <decui microsoft com>, me, adrain
Approved by: adrian
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D4762
While I'm there also correct typos in OptionalObsoleteFiles and add
information of the command line options for hv_kvp_daemon(8).
Reported by: jmg [1]
Reviewed by: jmg
MFC after: 2 weeks
to a directory. So instead of doing this, we just call mkdir(2)
directly and test if the returned value is 0 or errno is EISDIR.
Reported by: Coverity
CID: 1238925
MFC after: 1 week
many thanks for their continued support of FreeBSD.
While I'm there, also implement a new build knob, WITHOUT_HYPERV to
disable building and installing of the HyperV utilities when necessary.
The HyperV utilities are only built for i386 and amd64 targets.
This is a stable/10 candidate for inclusion with 10.1-RELEASE.
Submitted by: Wei Hu <weh microsoft com>
MFC after: 1 week
