AFS: Fix kafs module unloading
At present, it is not possible to successfully unload the kafs module if there are outstanding async outgoing calls (those made with afs_make_call()). This appears to be due to the changes introduced by: commit 05949945 Author: Tejun Heo <tj@kernel.org> Date: Fri Mar 7 10:24:50 2014 -0500 Subject: afs: don't use PREPARE_WORK which didn't go far enough. The problem is due to: (1) The aforementioned commit introduced a separate handler function pointer in the call, call->async_workfn, in addition to the original workqueue item, call->async_work, for asynchronous operations because workqueues subsystem cannot handle the workqueue item pointer being changed whilst the item is queued or being processed. (2) afs_async_workfn() was introduced in that commit to be the callback for call->async_work. Its sole purpose is to run whatever call->async_workfn points to. (3) call->async_workfn is only used from afs_async_workfn(), which is only set on async_work by afs_collect_incoming_call() - ie. for incoming calls. (4) call->async_workfn is *not* set by afs_make_call() when outgoing calls are made, and call->async_work is set afs_process_async_call() - and not afs_async_workfn(). (5) afs_process_async_call() now changes call->async_workfn rather than call->async_work to point to afs_delete_async_call() to clean up, but this is only effective for incoming calls because call->async_work does not point to afs_async_workfn() for outgoing calls. (6) Because, for incoming calls, call->async_work remains pointing to afs_process_async_call() this results in an infinite loop. Instead, make the workqueue uniformly vector through call->async_workfn, via afs_async_workfn() and simply initialise call->async_workfn to point to afs_process_async_call() in afs_make_call(). Signed-off-by: NNathaniel Wesley Filardo <nwf@cs.jhu.edu> Signed-off-by: NDavid Howells <dhowells@redhat.com> Reviewed-by: NTejun Heo <tj@kernel.org>
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