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| author | Chuck Lever <chuck.lever@oracle.com> | 2024-05-07 16:37:14 +0300 |
|---|---|---|
| committer | Chuck Lever <chuck.lever@oracle.com> | 2024-05-09 16:10:48 +0300 |
| commit | 8d915bbf39266bb66082c1e4980e123883f19830 (patch) | |
| tree | 1e060341ef961cbc9b379b47bb08556661ae4099 /fs/nfsd | |
| parent | bafa6b4d95d97877baa61883ff90f7e374427fae (diff) | |
| download | linux-8d915bbf39266bb66082c1e4980e123883f19830.tar.xz | |
NFSD: Force all NFSv4.2 COPY requests to be synchronous
We've discovered that delivering a CB_OFFLOAD operation can be
unreliable in some pretty unremarkable situations. Examples
include:
- The server dropped the connection because it lost a forechannel
NFSv4 request and wishes to force the client to retransmit
- The GSS sequence number window under-flowed
- A network partition occurred
When that happens, all pending callback operations, including
CB_OFFLOAD, are lost. NFSD does not retransmit them.
Moreover, the Linux NFS client does not yet support sending an
OFFLOAD_STATUS operation to probe whether an asynchronous COPY
operation has finished. Thus, on Linux NFS clients, when a
CB_OFFLOAD is lost, asynchronous COPY can hang until manually
interrupted.
I've tried a couple of remedies, but so far the side-effects are
worse than the disease and they have had to be reverted. So
temporarily force COPY operations to be synchronous so that the use
of CB_OFFLOAD is avoided entirely. This is a fix that can easily be
backported to LTS kernels. I am working on client patches that
introduce an implementation of OFFLOAD_STATUS.
Note that NFSD arbitrarily limits the size of a copy_file_range
to 4MB to avoid indefinitely blocking an nfsd thread. A short
COPY result is returned in that case, and the client can present
a fresh COPY request for the remainder.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Diffstat (limited to 'fs/nfsd')
| -rw-r--r-- | fs/nfsd/nfs4proc.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c index ea3cc3e870a7..46bd20fe5c0f 100644 --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1807,6 +1807,13 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, __be32 status; struct nfsd4_copy *async_copy = NULL; + /* + * Currently, async COPY is not reliable. Force all COPY + * requests to be synchronous to avoid client application + * hangs waiting for COPY completion. + */ + nfsd4_copy_set_sync(copy, true); + copy->cp_clp = cstate->clp; if (nfsd4_ssc_is_inter(copy)) { trace_nfsd_copy_inter(copy); |