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>

1 files changed, 12 insertions, 0 deletions

diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index 06cf218944c5..feeb6d4bdffd 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -532,6 +532,18 @@ struct nfsd4_copy {
 	struct nfsd4_callback	cp_cb;
 	__be32			nfserr;
 	struct knfsd_fh		fh;
+
+	struct nfs4_client      *cp_clp;
+
+	struct file             *file_src;
+	struct file             *file_dst;
+
+	stateid_t		cp_stateid;
+
+	struct list_head	copies;
+	struct task_struct	*copy_task;
+	refcount_t		refcount;
+	bool			stopped;
 };
 
 struct nfsd4_seek {