Add a function (slow_work_is_queued()) to permit the owner of a work item to
determine if the item is queued or not.
The work item is counted as being queued if it is actually on the queue, not
just if it is pending. If it is executing and pending, then it is not on the
queue, but will rather be put back on the queue when execution finishes.
This permits a caller to quickly work out if it may be able to put another,
dependent work item on the queue behind it, or whether it will have to wait
till that is finished.
This can be used by CacheFiles to work out whether the creation a new object
can be immediately deferred when it has to wait for an old object to be
deleted, or whether a wait must take place. If a wait is necessary, then the
slow-work thread can otherwise get blocked, preventing the deletion from
taking place.
Signed-off-by: David Howells <dhowells@redhat.com>
This adds support for starting slow work with a delay, similar
to the functionality we have for workqueues.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Add support for cancellation of queued slow work and delayed slow work items.
The cancellation functions will wait for items that are pending or undergoing
execution to be discarded by the slow work facility.
Attempting to enqueue work that is in the process of being cancelled will
result in ECANCELED.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Make the ability for the slow-work facility to take references on a work item
optional as not everyone requires this.
Even the internal slow-work stubs them out, so those can be got rid of too.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Wait for outstanding slow work items belonging to a module to clear when
unregistering that module as a user of the facility. This prevents the put_ref
code of a work item from being taken away before it returns.
Signed-off-by: David Howells <dhowells@redhat.com>
Document the slow work thread pool.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>
