registered in g_gate_units array and when its sc_provider field is
filled. If during this period g_gate_units is accessed by another
thread that is checking for provider name collision the crash is
possible.
Fix this by adding sc_name field to struct g_gate_softc. In
g_gate_create() when g_gate_softc is created but sc_provider is still
not sc_name points to provider name stored in the local array.
Approved by: pjd (mentor)
Reported by: Freddie Cash <fjwcash@gmail.com>
MFC after: 1 week
HAST allows to transparently store data on two physically separated machines
connected over the TCP/IP network. HAST works in Primary-Secondary
(Master-Backup, Master-Slave) configuration, which means that only one of the
cluster nodes can be active at any given time. Only Primary node is able to
handle I/O requests to HAST-managed devices. Currently HAST is limited to two
cluster nodes in total.
HAST operates on block level - it provides disk-like devices in /dev/hast/
directory for use by file systems and/or applications. Working on block level
makes it transparent for file systems and applications. There in no difference
between using HAST-provided device and raw disk, partition, etc. All of them
are just regular GEOM providers in FreeBSD.
For more information please consult hastd(8), hastctl(8) and hast.conf(5)
manual pages, as well as http://wiki.FreeBSD.org/HAST.
Sponsored by: FreeBSD Foundation
Sponsored by: OMCnet Internet Service GmbH
Sponsored by: TransIP BV
- hold/release device in start/done routines, this will probably slow
down things a bit, but previous code was racy;
- only release device if g_gate_destroy() failed - if it succeeded device
is dead and there is nothing to release;
- various other changes which makes forcible destruction reliable.
MFC after: 3 days
4 mutex operations per I/O requests.
- Use only one mutex to protect both (incoming and outgoing) queue.
As MUTEX_PROFILING(9) shows, there is no big contention for this lock.
- Protect sc_queue_count with queue mutex, instead of doing atomic
operations on it.
- Remove DROP_GIANT()/PICKUP_GIANT() - ggate is marked as MPSAFE and no
Giant there.
