If a write delegation isn't available, the Linux NFS client uses
a zero-stateid when performing a SETATTR.
NFSv4.0 provides no mechanism for an NFS server to match such a
request to a particular client. It recalls all delegations for that
file, even delegations held by the client issuing the request. If
that client happens to hold a read delegation, the server will
recall it immediately, resulting in an NFS4ERR_DELAY/CB_RECALL/
DELEGRETURN sequence.
Optimize out this pipeline bubble by having the client return any
delegations it may hold on a file before it issues a
SETATTR(zero-stateid) on that file.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
fs/nfs/nfs4proc.c | 2 ++
1 file changed, 2 insertions(+)
Changes since v1:
- Return the delegation only for NFSv4.0 mounts
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index dbd01548335b..bca7245f1e78 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3314,6 +3314,8 @@ static int _nfs4_do_setattr(struct inode *inode,
goto zero_stateid;
} else {
zero_stateid:
+ if (server->nfs_client->cl_minorversion == 0)
+ nfs4_inode_return_delegation(inode);
nfs4_stateid_copy(&arg->stateid, &zero_stateid);
}
if (delegation_cred)
