common: link mds/flock.o to libcommon

later commit will use this code to track file locks held by cephfs
client.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: posix file lock support

Signed-off-by: Yan, Zheng <zyan@redhat.com>
fuse: enable fuse_multithreaded by default

GETFILELOCK MDS request may block for a long time, so we need to
use multithread event loop,

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: add helper function that updates lock state

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: register callback for fuse interrupt

libfuse allows program to reigster a callback for interrupt. When a file
system operation is interrupted, the fuse kernel driver sends interupt
request to libfuse. libfuse calls the interrupt callback when receiving
interrupt request.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: allow interrupting blocked file lock operation

This commit introduce two new types of setfilelock request. Unlike
setfilelock (UNLOCK) request, these two new types of setfilelock request
do not drop locks that have alread been acquired, they only interrupt
blocked setfilelock request.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: use atomic variable to track reference of MetaRequeset

this allow us to increase reference count of MetaRequest while not holding
the client_lock

Signed-off-by: Yan, Zheng <zyan@redhat.com>
client: use finisher to abort MDS request

When a request is interrupted, libfuse first locks an internal mutex,
then calls the interrupt callback. libfuse need to lock the same mutex
when unregistering interrupt callback. We unregister interrupt callback
while client_lock is locked, so we can't acquiring the client_lock in
the interrupt callback.

Signed-off-by: Yan, Zheng <zyan@redhat.com>
mds: reply -EOPNOTSUPP for unknown lock type

Signed-off-by: Yan, Zheng <zyan@redhat.com>
mds: fix neighbor lock check

Signed-off-by: Yan, Zheng <zyan@redhat.com>
qa/workunits/fs/misc: Add a workunit for file lock interruption

Signed-off-by: Yan, Zheng <zyan@redhat.com>
Merge pull request #2628 from ceph/wip-client-flock

Wip client flock

Add support for file locking to the userspace client, and improve blocked-lock cancellation so that it doesn't remove locks that succeeded when racing.

Reviewed-by: Greg Farnum <greg@inktank.com>