NFS: Use NFSv4.2's OFFLOAD_STATUS operation

We've found that there are cases where a transport disconnection
results in the loss of callback RPCs. NFS servers typically do not
retransmit callback operations after a disconnect.

This can be a problem for the Linux NFS client's current
implementation of asynchronous COPY, which waits indefinitely for a
CB_OFFLOAD callback. If a transport disconnect occurs while an async
COPY is running, there's a good chance the client will never get the
completing CB_OFFLOAD.

Fix this by implementing the OFFLOAD_STATUS operation so that the
Linux NFS client can probe the NFS server if it doesn't see a
CB_OFFLOAD in a reasonable amount of time.

This patch implements a simplistic check. As future work, the client
might also be able to detect whether there is no forward progress on
the request asynchronous COPY operation, and CANCEL it.

Suggested-by: Olga Kornievskaia <kolga@netapp.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218735
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Link: https://lore.kernel.org/r/20250113153235.48706-15-cel@kernel.org
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
index 3e359e16c324927aefc444b496d2403b7021767c..82ada136ee6a96c97784a532e277ee597d0c4a60 100644 (file)
--- a/fs/nfs/nfs42proc.c
+++ b/fs/nfs/nfs42proc.c
@@ -175,6 +175,20 @@ int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
        return err;
 }
 
+static void nfs4_copy_dequeue_callback(struct nfs_server *dst_server,
+                                      struct nfs_server *src_server,
+                                      struct nfs4_copy_state *copy)
+{
+       spin_lock(&dst_server->nfs_client->cl_lock);
+       list_del_init(&copy->copies);
+       spin_unlock(&dst_server->nfs_client->cl_lock);
+       if (dst_server != src_server) {
+               spin_lock(&src_server->nfs_client->cl_lock);
+               list_del_init(&copy->src_copies);
+               spin_unlock(&src_server->nfs_client->cl_lock);
+       }
+}
+
 static int handle_async_copy(struct nfs42_copy_res *res,
                             struct nfs_server *dst_server,
                             struct nfs_server *src_server,
@@ -184,9 +198,12 @@ static int handle_async_copy(struct nfs42_copy_res *res,
                             bool *restart)
 {
        struct nfs4_copy_state *copy, *tmp_copy = NULL, *iter;
-       int status = NFS4_OK;
        struct nfs_open_context *dst_ctx = nfs_file_open_context(dst);
        struct nfs_open_context *src_ctx = nfs_file_open_context(src);
+       struct nfs_client *clp = dst_server->nfs_client;
+       unsigned long timeout = 3 * HZ;
+       int status = NFS4_OK;
+       u64 copied;
 
        copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_KERNEL);
        if (!copy)
@@ -224,15 +241,12 @@ static int handle_async_copy(struct nfs42_copy_res *res,
                spin_unlock(&src_server->nfs_client->cl_lock);
        }
 
-       status = wait_for_completion_interruptible(&copy->completion);
-       spin_lock(&dst_server->nfs_client->cl_lock);
-       list_del_init(&copy->copies);
-       spin_unlock(&dst_server->nfs_client->cl_lock);
-       if (dst_server != src_server) {
-               spin_lock(&src_server->nfs_client->cl_lock);
-               list_del_init(&copy->src_copies);
-               spin_unlock(&src_server->nfs_client->cl_lock);
-       }
+wait:
+       status = wait_for_completion_interruptible_timeout(&copy->completion,
+                                                          timeout);
+       if (!status)
+               goto timeout;
+       nfs4_copy_dequeue_callback(dst_server, src_server, copy);
        if (status == -ERESTARTSYS) {
                goto out_cancel;
        } else if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
@@ -242,6 +256,7 @@ static int handle_async_copy(struct nfs42_copy_res *res,
        }
 out:
        res->write_res.count = copy->count;
+       /* Copy out the updated write verifier provided by CB_OFFLOAD. */
        memcpy(&res->write_res.verifier, &copy->verf, sizeof(copy->verf));
        status = -copy->error;
 
@@ -253,6 +268,39 @@ out_cancel:
        if (!nfs42_files_from_same_server(src, dst))
                nfs42_do_offload_cancel_async(src, src_stateid);
        goto out_free;
+timeout:
+       timeout <<= 1;
+       if (timeout > (clp->cl_lease_time >> 1))
+               timeout = clp->cl_lease_time >> 1;
+       status = nfs42_proc_offload_status(dst, &copy->stateid, &copied);
+       if (status == -EINPROGRESS)
+               goto wait;
+       nfs4_copy_dequeue_callback(dst_server, src_server, copy);
+       switch (status) {
+       case 0:
+               /* The server recognized the copy stateid, so it hasn't
+                * rebooted. Don't overwrite the verifier returned in the
+                * COPY result. */
+               res->write_res.count = copied;
+               goto out_free;
+       case -EREMOTEIO:
+               /* COPY operation failed on the server. */
+               status = -EOPNOTSUPP;
+               res->write_res.count = copied;
+               goto out_free;
+       case -EBADF:
+               /* Server did not recognize the copy stateid. It has
+                * probably restarted and lost the plot. */
+               res->write_res.count = 0;
+               status = -EOPNOTSUPP;
+               break;
+       case -EOPNOTSUPP:
+               /* RFC 7862 REQUIREs server to support OFFLOAD_STATUS when
+                * it has signed up for an async COPY, so server is not
+                * spec-compliant. */
+               res->write_res.count = 0;
+       }
+       goto out_free;
 }
 
 static int process_copy_commit(struct file *dst, loff_t pos_dst,
@@ -643,7 +691,7 @@ _nfs42_proc_offload_status(struct nfs_server *server, struct file *file,
  * Other negative errnos indicate the client could not complete the
  * request.
  */
-static int __maybe_unused
+static int
 nfs42_proc_offload_status(struct file *dst, nfs4_stateid *stateid, u64 *copied)
 {
        struct inode *inode = file_inode(dst);