NFSD introduce async copy feature
Upon receiving a request for async copy, create a new kthread. If we get asynchronous request, make sure to copy the needed arguments/state from the stack before starting the copy. Then start the thread and reply back to the client indicating copy is asynchronous. nfsd_copy_file_range() will copy in a loop over the total number of bytes is needed to copy. In case a failure happens in the middle, we ignore the error and return how much we copied so far. Once done creating a workitem for the callback workqueue and send CB_OFFLOAD with the results. The lifetime of the copy stateid is bound to the vfs copy. This way we don't need to keep the nfsd_net structure for the callback. We could keep it around longer so that an OFFLOAD_STATUS that came late would still get results, but clients should be able to deal without that. We handle OFFLOAD_CANCEL by sending a signal to the copy thread and calling kthread_stop. A client should cancel any ongoing copies before calling DESTROY_CLIENT; if not, we return a CLIENT_BUSY error. If the client is destroyed for some other reason (lease expiration, or server shutdown), we must clean up any ongoing copies ourselves. Signed-off-by: Olga Kornievskaia <kolga@netapp.com> [colin.king@canonical.com: fix leak in error case] [bfields@fieldses.org: remove signalling, merge patches] Signed-off-by: J. Bruce Fields <bfields@redhat.com>
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