diff mbox series

[RFC,4/4] NFS: Implement NFSv4.2's OFFLOAD_STATUS operation

Message ID 20240429151632.212571-10-cel@kernel.org (mailing list archive)
State New
Headers show
Series NFSv4.2 OFFLOAD_STATUS for the Linux NFS client | expand

Commit Message

Chuck Lever April 29, 2024, 3:16 p.m. UTC
From: Chuck Lever <chuck.lever@oracle.com>

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 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
matching 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
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfs/nfs42proc.c        | 100 +++++++++++++++++++++++++++++++++++---
 fs/nfs/nfs4trace.h        |   1 +
 include/linux/nfs_fs_sb.h |   1 +
 3 files changed, 96 insertions(+), 6 deletions(-)

Comments

Olga Kornievskaia April 29, 2024, 3:35 p.m. UTC | #1
On Mon, Apr 29, 2024 at 11:22 AM <cel@kernel.org> wrote:
>
> From: Chuck Lever <chuck.lever@oracle.com>
>
> 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 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
> matching 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.

I think this patch series needs a bit more nuances
(1) if we know that server doesn't support offload_status we might as
well wait uninterrupted perhaps? but I can see how as you mentioned we
might want to measure no forward progress and cancel the copy and
fallback to read/write.
(2) we can't really go back to the "wait" after failing a
offload_status as the cb_offload callback might have already arrived
and I think we need to walk the pending_cb_callbacks to make sure we
haven't received it before waiting again (otherwise, we'd wait
forever).
(3) then also there is the case where we woke up and sent the
offload_status and got a 'copy finished' reply but we also got the
cb_callback reply as well and the copy things need to be cleaned up
now.

>
> Suggested-by: Olga Kornievskaia <kolga@netapp.com>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=218735
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  fs/nfs/nfs42proc.c        | 100 +++++++++++++++++++++++++++++++++++---
>  fs/nfs/nfs4trace.h        |   1 +
>  include/linux/nfs_fs_sb.h |   1 +
>  3 files changed, 96 insertions(+), 6 deletions(-)
>
> diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> index 7656d7c103fa..224fb3b8696a 100644
> --- a/fs/nfs/nfs42proc.c
> +++ b/fs/nfs/nfs42proc.c
> @@ -21,6 +21,7 @@
>
>  #define NFSDBG_FACILITY NFSDBG_PROC
>  static int nfs42_do_offload_cancel_async(struct file *dst, nfs4_stateid *std);
> +static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid);
>
>  static void nfs42_set_netaddr(struct file *filep, struct nfs42_netaddr *naddr)
>  {
> @@ -173,6 +174,9 @@ int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
>         return err;
>  }
>
> +/* Wait this long before checking progress on a COPY operation */
> +#define NFS42_COPY_TIMEOUT     (7 * HZ)
> +
>  static int handle_async_copy(struct nfs42_copy_res *res,
>                              struct nfs_server *dst_server,
>                              struct nfs_server *src_server,
> @@ -222,7 +226,9 @@ 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);
> +wait:
> +       status = wait_for_completion_interruptible_timeout(&copy->completion,
> +                                                          NFS42_COPY_TIMEOUT);
>         spin_lock(&dst_server->nfs_client->cl_lock);
>         list_del_init(&copy->copies);
>         spin_unlock(&dst_server->nfs_client->cl_lock);
> @@ -231,12 +237,20 @@ static int handle_async_copy(struct nfs42_copy_res *res,
>                 list_del_init(&copy->src_copies);
>                 spin_unlock(&src_server->nfs_client->cl_lock);
>         }
> -       if (status == -ERESTARTSYS) {
> -               goto out_cancel;
> -       } else if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
> -               status = -EAGAIN;
> -               *restart = true;
> +       switch (status) {
> +       case 0:
> +               status = nfs42_proc_offload_status(src, src_stateid);
> +               if (status && status != -EOPNOTSUPP)
> +                       goto wait;
> +               break;
> +       case -ERESTARTSYS:
>                 goto out_cancel;
> +       default:
> +               if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
> +                       status = -EAGAIN;
> +                       *restart = true;
> +                       goto out_cancel;
> +               }
>         }
>  out:
>         res->write_res.count = copy->count;
> @@ -582,6 +596,80 @@ static int nfs42_do_offload_cancel_async(struct file *dst,
>         return status;
>  }
>
> +static void nfs42_offload_status_prepare(struct rpc_task *task, void *calldata)
> +{
> +       struct nfs42_offload_data *data = calldata;
> +
> +       nfs4_setup_sequence(data->seq_server->nfs_client,
> +                               &data->args.osa_seq_args,
> +                               &data->res.osr_seq_res, task);
> +}
> +
> +static void nfs42_offload_status_done(struct rpc_task *task, void *calldata)
> +{
> +       struct nfs42_offload_data *data = calldata;
> +
> +       trace_nfs4_offload_status(&data->args, task->tk_status);
> +       nfs41_sequence_done(task, &data->res.osr_seq_res);
> +       if (task->tk_status &&
> +               nfs4_async_handle_error(task, data->seq_server, NULL,
> +                       NULL) == -EAGAIN)
> +               rpc_restart_call_prepare(task);
> +}
> +
> +static const struct rpc_call_ops nfs42_offload_status_ops = {
> +       .rpc_call_prepare = nfs42_offload_status_prepare,
> +       .rpc_call_done = nfs42_offload_status_done,
> +       .rpc_release = nfs42_free_offload_data,
> +};
> +
> +static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid)
> +{
> +       struct nfs_open_context *ctx = nfs_file_open_context(file);
> +       struct nfs_server *server = NFS_SERVER(file_inode(file));
> +       struct nfs42_offload_data *data = NULL;
> +       struct rpc_task *task;
> +       struct rpc_message msg = {
> +               .rpc_proc       = &nfs4_procedures[NFSPROC4_CLNT_OFFLOAD_STATUS],
> +               .rpc_cred       = ctx->cred,
> +       };
> +       struct rpc_task_setup task_setup_data = {
> +               .rpc_client     = server->client,
> +               .rpc_message    = &msg,
> +               .callback_ops   = &nfs42_offload_status_ops,
> +               .workqueue      = nfsiod_workqueue,
> +               .flags          = RPC_TASK_ASYNC | RPC_TASK_SOFTCONN,
> +       };
> +       int status;
> +
> +       if (!(server->caps & NFS_CAP_OFFLOAD_STATUS))
> +               return -EOPNOTSUPP;
> +
> +       data = kzalloc(sizeof(struct nfs42_offload_data), GFP_KERNEL);
> +       if (data == NULL)
> +               return -ENOMEM;
> +
> +       data->seq_server = server;
> +       data->args.osa_src_fh = NFS_FH(file_inode(file));
> +       memcpy(&data->args.osa_stateid, stateid,
> +               sizeof(data->args.osa_stateid));
> +       msg.rpc_argp = &data->args;
> +       msg.rpc_resp = &data->res;
> +       task_setup_data.callback_data = data;
> +       nfs4_init_sequence(&data->args.osa_seq_args, &data->res.osr_seq_res,
> +                          1, 0);
> +       task = rpc_run_task(&task_setup_data);
> +       if (IS_ERR(task)) {
> +               nfs42_free_offload_data(data);
> +               return PTR_ERR(task);
> +       }
> +       status = rpc_wait_for_completion_task(task);
> +       if (status == -ENOTSUPP)
> +               server->caps &= ~NFS_CAP_OFFLOAD_STATUS;
> +       rpc_put_task(task);
> +       return status;
> +}
> +
>  static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
>                                    struct nfs42_copy_notify_args *args,
>                                    struct nfs42_copy_notify_res *res)
> diff --git a/fs/nfs/nfs4trace.h b/fs/nfs/nfs4trace.h
> index 8f32dbf9c91d..9bcc525c71d1 100644
> --- a/fs/nfs/nfs4trace.h
> +++ b/fs/nfs/nfs4trace.h
> @@ -2564,6 +2564,7 @@ DECLARE_EVENT_CLASS(nfs4_offload_class,
>                         ), \
>                         TP_ARGS(args, error))
>  DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_cancel);
> +DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_status);
>
>  DECLARE_EVENT_CLASS(nfs4_xattr_event,
>                 TP_PROTO(
> diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> index 92de074e63b9..0937e73c4767 100644
> --- a/include/linux/nfs_fs_sb.h
> +++ b/include/linux/nfs_fs_sb.h
> @@ -278,6 +278,7 @@ struct nfs_server {
>  #define NFS_CAP_LGOPEN         (1U << 5)
>  #define NFS_CAP_CASE_INSENSITIVE       (1U << 6)
>  #define NFS_CAP_CASE_PRESERVING        (1U << 7)
> +#define NFS_CAP_OFFLOAD_STATUS (1U << 8)
>  #define NFS_CAP_POSIX_LOCK     (1U << 14)
>  #define NFS_CAP_UIDGID_NOMAP   (1U << 15)
>  #define NFS_CAP_STATEID_NFSV41 (1U << 16)
> --
> 2.44.0
>
>
Chuck Lever April 29, 2024, 4:12 p.m. UTC | #2
On Mon, Apr 29, 2024 at 11:35:20AM -0400, Olga Kornievskaia wrote:
> On Mon, Apr 29, 2024 at 11:22 AM <cel@kernel.org> wrote:
> >
> > From: Chuck Lever <chuck.lever@oracle.com>
> >
> > 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 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
> > matching 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.
> 
> I think this patch series needs a bit more nuances
> (1) if we know that server doesn't support offload_status we might as
> well wait uninterrupted perhaps? but I can see how as you mentioned we
> might want to measure no forward progress and cancel the copy and
> fallback to read/write.

The client doesn't know whether the server supports OFFLOAD_STATUS
until the first OFFLOAD_STATUS is sent. So at least /one/ of those
waits will be of the timeout variety, no matter what.

We can mitigate the cost of waking up periodically by making
NFS42_COPY_TIMEOUT longer than 7 seconds. That's just a number I
pulled out of the air.


> (2) we can't really go back to the "wait" after failing a
> offload_status as the cb_offload callback might have already arrived
> and I think we need to walk the pending_cb_callbacks to make sure we
> haven't received it before waiting again (otherwise, we'd wait
> forever).

IIUC the wait_for_completion() family of APIs does not sleep at all
if the completion has already been marked "done". So in that case
wfc() should just return a positive number and execution drops into
the "copy complete" code.


> (3) then also there is the case where we woke up and sent the
> offload_status and got a 'copy finished' reply but we also got the
> cb_callback reply as well and the copy things need to be cleaned up
> now.

The callback reply should just wake the completion, even though
there might no longer be a waiter, and then free the call data. That
seems OK.

I think what I missed is that the call data needs to be cleaned
up when we are sure the CB_OFFLOAD was lost, otherwise it leaks.
Will need to think about that. How is that done if the client
detects a server restart?

Also nfs42_proc_offload_status() needs to distinguish between "still
running," "all done," "bad stateid," and "no answer".


> > Suggested-by: Olga Kornievskaia <kolga@netapp.com>
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218735
> > Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> > ---
> >  fs/nfs/nfs42proc.c        | 100 +++++++++++++++++++++++++++++++++++---
> >  fs/nfs/nfs4trace.h        |   1 +
> >  include/linux/nfs_fs_sb.h |   1 +
> >  3 files changed, 96 insertions(+), 6 deletions(-)
> >
> > diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
> > index 7656d7c103fa..224fb3b8696a 100644
> > --- a/fs/nfs/nfs42proc.c
> > +++ b/fs/nfs/nfs42proc.c
> > @@ -21,6 +21,7 @@
> >
> >  #define NFSDBG_FACILITY NFSDBG_PROC
> >  static int nfs42_do_offload_cancel_async(struct file *dst, nfs4_stateid *std);
> > +static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid);
> >
> >  static void nfs42_set_netaddr(struct file *filep, struct nfs42_netaddr *naddr)
> >  {
> > @@ -173,6 +174,9 @@ int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
> >         return err;
> >  }
> >
> > +/* Wait this long before checking progress on a COPY operation */
> > +#define NFS42_COPY_TIMEOUT     (7 * HZ)
> > +
> >  static int handle_async_copy(struct nfs42_copy_res *res,
> >                              struct nfs_server *dst_server,
> >                              struct nfs_server *src_server,
> > @@ -222,7 +226,9 @@ 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);
> > +wait:
> > +       status = wait_for_completion_interruptible_timeout(&copy->completion,
> > +                                                          NFS42_COPY_TIMEOUT);
> >         spin_lock(&dst_server->nfs_client->cl_lock);
> >         list_del_init(&copy->copies);
> >         spin_unlock(&dst_server->nfs_client->cl_lock);
> > @@ -231,12 +237,20 @@ static int handle_async_copy(struct nfs42_copy_res *res,
> >                 list_del_init(&copy->src_copies);
> >                 spin_unlock(&src_server->nfs_client->cl_lock);
> >         }
> > -       if (status == -ERESTARTSYS) {
> > -               goto out_cancel;
> > -       } else if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
> > -               status = -EAGAIN;
> > -               *restart = true;
> > +       switch (status) {
> > +       case 0:
> > +               status = nfs42_proc_offload_status(src, src_stateid);
> > +               if (status && status != -EOPNOTSUPP)
> > +                       goto wait;
> > +               break;
> > +       case -ERESTARTSYS:
> >                 goto out_cancel;
> > +       default:
> > +               if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
> > +                       status = -EAGAIN;
> > +                       *restart = true;
> > +                       goto out_cancel;
> > +               }
> >         }
> >  out:
> >         res->write_res.count = copy->count;
> > @@ -582,6 +596,80 @@ static int nfs42_do_offload_cancel_async(struct file *dst,
> >         return status;
> >  }
> >
> > +static void nfs42_offload_status_prepare(struct rpc_task *task, void *calldata)
> > +{
> > +       struct nfs42_offload_data *data = calldata;
> > +
> > +       nfs4_setup_sequence(data->seq_server->nfs_client,
> > +                               &data->args.osa_seq_args,
> > +                               &data->res.osr_seq_res, task);
> > +}
> > +
> > +static void nfs42_offload_status_done(struct rpc_task *task, void *calldata)
> > +{
> > +       struct nfs42_offload_data *data = calldata;
> > +
> > +       trace_nfs4_offload_status(&data->args, task->tk_status);
> > +       nfs41_sequence_done(task, &data->res.osr_seq_res);
> > +       if (task->tk_status &&
> > +               nfs4_async_handle_error(task, data->seq_server, NULL,
> > +                       NULL) == -EAGAIN)
> > +               rpc_restart_call_prepare(task);
> > +}
> > +
> > +static const struct rpc_call_ops nfs42_offload_status_ops = {
> > +       .rpc_call_prepare = nfs42_offload_status_prepare,
> > +       .rpc_call_done = nfs42_offload_status_done,
> > +       .rpc_release = nfs42_free_offload_data,
> > +};
> > +
> > +static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid)
> > +{
> > +       struct nfs_open_context *ctx = nfs_file_open_context(file);
> > +       struct nfs_server *server = NFS_SERVER(file_inode(file));
> > +       struct nfs42_offload_data *data = NULL;
> > +       struct rpc_task *task;
> > +       struct rpc_message msg = {
> > +               .rpc_proc       = &nfs4_procedures[NFSPROC4_CLNT_OFFLOAD_STATUS],
> > +               .rpc_cred       = ctx->cred,
> > +       };
> > +       struct rpc_task_setup task_setup_data = {
> > +               .rpc_client     = server->client,
> > +               .rpc_message    = &msg,
> > +               .callback_ops   = &nfs42_offload_status_ops,
> > +               .workqueue      = nfsiod_workqueue,
> > +               .flags          = RPC_TASK_ASYNC | RPC_TASK_SOFTCONN,
> > +       };
> > +       int status;
> > +
> > +       if (!(server->caps & NFS_CAP_OFFLOAD_STATUS))
> > +               return -EOPNOTSUPP;
> > +
> > +       data = kzalloc(sizeof(struct nfs42_offload_data), GFP_KERNEL);
> > +       if (data == NULL)
> > +               return -ENOMEM;
> > +
> > +       data->seq_server = server;
> > +       data->args.osa_src_fh = NFS_FH(file_inode(file));
> > +       memcpy(&data->args.osa_stateid, stateid,
> > +               sizeof(data->args.osa_stateid));
> > +       msg.rpc_argp = &data->args;
> > +       msg.rpc_resp = &data->res;
> > +       task_setup_data.callback_data = data;
> > +       nfs4_init_sequence(&data->args.osa_seq_args, &data->res.osr_seq_res,
> > +                          1, 0);
> > +       task = rpc_run_task(&task_setup_data);
> > +       if (IS_ERR(task)) {
> > +               nfs42_free_offload_data(data);
> > +               return PTR_ERR(task);
> > +       }
> > +       status = rpc_wait_for_completion_task(task);
> > +       if (status == -ENOTSUPP)
> > +               server->caps &= ~NFS_CAP_OFFLOAD_STATUS;
> > +       rpc_put_task(task);
> > +       return status;
> > +}
> > +
> >  static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
> >                                    struct nfs42_copy_notify_args *args,
> >                                    struct nfs42_copy_notify_res *res)
> > diff --git a/fs/nfs/nfs4trace.h b/fs/nfs/nfs4trace.h
> > index 8f32dbf9c91d..9bcc525c71d1 100644
> > --- a/fs/nfs/nfs4trace.h
> > +++ b/fs/nfs/nfs4trace.h
> > @@ -2564,6 +2564,7 @@ DECLARE_EVENT_CLASS(nfs4_offload_class,
> >                         ), \
> >                         TP_ARGS(args, error))
> >  DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_cancel);
> > +DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_status);
> >
> >  DECLARE_EVENT_CLASS(nfs4_xattr_event,
> >                 TP_PROTO(
> > diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
> > index 92de074e63b9..0937e73c4767 100644
> > --- a/include/linux/nfs_fs_sb.h
> > +++ b/include/linux/nfs_fs_sb.h
> > @@ -278,6 +278,7 @@ struct nfs_server {
> >  #define NFS_CAP_LGOPEN         (1U << 5)
> >  #define NFS_CAP_CASE_INSENSITIVE       (1U << 6)
> >  #define NFS_CAP_CASE_PRESERVING        (1U << 7)
> > +#define NFS_CAP_OFFLOAD_STATUS (1U << 8)
> >  #define NFS_CAP_POSIX_LOCK     (1U << 14)
> >  #define NFS_CAP_UIDGID_NOMAP   (1U << 15)
> >  #define NFS_CAP_STATEID_NFSV41 (1U << 16)
> > --
> > 2.44.0
> >
> >
diff mbox series

Patch

diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
index 7656d7c103fa..224fb3b8696a 100644
--- a/fs/nfs/nfs42proc.c
+++ b/fs/nfs/nfs42proc.c
@@ -21,6 +21,7 @@ 
 
 #define NFSDBG_FACILITY NFSDBG_PROC
 static int nfs42_do_offload_cancel_async(struct file *dst, nfs4_stateid *std);
+static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid);
 
 static void nfs42_set_netaddr(struct file *filep, struct nfs42_netaddr *naddr)
 {
@@ -173,6 +174,9 @@  int nfs42_proc_deallocate(struct file *filep, loff_t offset, loff_t len)
 	return err;
 }
 
+/* Wait this long before checking progress on a COPY operation */
+#define NFS42_COPY_TIMEOUT	(7 * HZ)
+
 static int handle_async_copy(struct nfs42_copy_res *res,
 			     struct nfs_server *dst_server,
 			     struct nfs_server *src_server,
@@ -222,7 +226,9 @@  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);
+wait:
+	status = wait_for_completion_interruptible_timeout(&copy->completion,
+							   NFS42_COPY_TIMEOUT);
 	spin_lock(&dst_server->nfs_client->cl_lock);
 	list_del_init(&copy->copies);
 	spin_unlock(&dst_server->nfs_client->cl_lock);
@@ -231,12 +237,20 @@  static int handle_async_copy(struct nfs42_copy_res *res,
 		list_del_init(&copy->src_copies);
 		spin_unlock(&src_server->nfs_client->cl_lock);
 	}
-	if (status == -ERESTARTSYS) {
-		goto out_cancel;
-	} else if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
-		status = -EAGAIN;
-		*restart = true;
+	switch (status) {
+	case 0:
+		status = nfs42_proc_offload_status(src, src_stateid);
+		if (status && status != -EOPNOTSUPP)
+			goto wait;
+		break;
+	case -ERESTARTSYS:
 		goto out_cancel;
+	default:
+		if (copy->flags || copy->error == NFS4ERR_PARTNER_NO_AUTH) {
+			status = -EAGAIN;
+			*restart = true;
+			goto out_cancel;
+		}
 	}
 out:
 	res->write_res.count = copy->count;
@@ -582,6 +596,80 @@  static int nfs42_do_offload_cancel_async(struct file *dst,
 	return status;
 }
 
+static void nfs42_offload_status_prepare(struct rpc_task *task, void *calldata)
+{
+	struct nfs42_offload_data *data = calldata;
+
+	nfs4_setup_sequence(data->seq_server->nfs_client,
+				&data->args.osa_seq_args,
+				&data->res.osr_seq_res, task);
+}
+
+static void nfs42_offload_status_done(struct rpc_task *task, void *calldata)
+{
+	struct nfs42_offload_data *data = calldata;
+
+	trace_nfs4_offload_status(&data->args, task->tk_status);
+	nfs41_sequence_done(task, &data->res.osr_seq_res);
+	if (task->tk_status &&
+		nfs4_async_handle_error(task, data->seq_server, NULL,
+			NULL) == -EAGAIN)
+		rpc_restart_call_prepare(task);
+}
+
+static const struct rpc_call_ops nfs42_offload_status_ops = {
+	.rpc_call_prepare = nfs42_offload_status_prepare,
+	.rpc_call_done = nfs42_offload_status_done,
+	.rpc_release = nfs42_free_offload_data,
+};
+
+static int nfs42_proc_offload_status(struct file *file, nfs4_stateid *stateid)
+{
+	struct nfs_open_context *ctx = nfs_file_open_context(file);
+	struct nfs_server *server = NFS_SERVER(file_inode(file));
+	struct nfs42_offload_data *data = NULL;
+	struct rpc_task *task;
+	struct rpc_message msg = {
+		.rpc_proc	= &nfs4_procedures[NFSPROC4_CLNT_OFFLOAD_STATUS],
+		.rpc_cred	= ctx->cred,
+	};
+	struct rpc_task_setup task_setup_data = {
+		.rpc_client	= server->client,
+		.rpc_message	= &msg,
+		.callback_ops	= &nfs42_offload_status_ops,
+		.workqueue	= nfsiod_workqueue,
+		.flags		= RPC_TASK_ASYNC | RPC_TASK_SOFTCONN,
+	};
+	int status;
+
+	if (!(server->caps & NFS_CAP_OFFLOAD_STATUS))
+		return -EOPNOTSUPP;
+
+	data = kzalloc(sizeof(struct nfs42_offload_data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	data->seq_server = server;
+	data->args.osa_src_fh = NFS_FH(file_inode(file));
+	memcpy(&data->args.osa_stateid, stateid,
+		sizeof(data->args.osa_stateid));
+	msg.rpc_argp = &data->args;
+	msg.rpc_resp = &data->res;
+	task_setup_data.callback_data = data;
+	nfs4_init_sequence(&data->args.osa_seq_args, &data->res.osr_seq_res,
+			   1, 0);
+	task = rpc_run_task(&task_setup_data);
+	if (IS_ERR(task)) {
+		nfs42_free_offload_data(data);
+		return PTR_ERR(task);
+	}
+	status = rpc_wait_for_completion_task(task);
+	if (status == -ENOTSUPP)
+		server->caps &= ~NFS_CAP_OFFLOAD_STATUS;
+	rpc_put_task(task);
+	return status;
+}
+
 static int _nfs42_proc_copy_notify(struct file *src, struct file *dst,
 				   struct nfs42_copy_notify_args *args,
 				   struct nfs42_copy_notify_res *res)
diff --git a/fs/nfs/nfs4trace.h b/fs/nfs/nfs4trace.h
index 8f32dbf9c91d..9bcc525c71d1 100644
--- a/fs/nfs/nfs4trace.h
+++ b/fs/nfs/nfs4trace.h
@@ -2564,6 +2564,7 @@  DECLARE_EVENT_CLASS(nfs4_offload_class,
 			), \
 			TP_ARGS(args, error))
 DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_cancel);
+DEFINE_NFS4_OFFLOAD_EVENT(nfs4_offload_status);
 
 DECLARE_EVENT_CLASS(nfs4_xattr_event,
 		TP_PROTO(
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index 92de074e63b9..0937e73c4767 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -278,6 +278,7 @@  struct nfs_server {
 #define NFS_CAP_LGOPEN		(1U << 5)
 #define NFS_CAP_CASE_INSENSITIVE	(1U << 6)
 #define NFS_CAP_CASE_PRESERVING	(1U << 7)
+#define NFS_CAP_OFFLOAD_STATUS	(1U << 8)
 #define NFS_CAP_POSIX_LOCK	(1U << 14)
 #define NFS_CAP_UIDGID_NOMAP	(1U << 15)
 #define NFS_CAP_STATEID_NFSV41	(1U << 16)