[PATCH v3 6/7] NFS: Use NFSv4.2's OFFLOAD_STATUS operation

cel
2025-01-13T15:32:51Z

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>
---
fs/nfs/nfs42proc.c | 70 ++++++++++++++++++++++++++++++++++++++--------
1 file changed, 59 insertions(+), 11 deletions(-)

diff --git a/fs/nfs/nfs42proc.c b/fs/nfs/nfs42proc.c
index 23508669d051..4baa66cd966a 100644
--- 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 @@ static int handle_async_copy(struct nfs42_copy_res *res,
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);
--
2.47.0