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 | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
Changes since v2:
- Return the delegation only for NFSv4.0 non-truncate cases
Changes since v1:
- Return the delegation only for NFSv4.0 mounts
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index f8946b9468ef..099ae32981a2 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3293,8 +3293,10 @@ static int _nfs4_do_setattr(struct inode *inode,
/* Servers should only apply open mode checks for file size changes */
truncate = (arg->iap->ia_valid & ATTR_SIZE) ? true : false;
- if (!truncate)
+ if (!truncate) {
+ nfs4_inode_make_writeable(inode);
goto zero_stateid;
+ }
if (nfs4_copy_delegation_stateid(inode, FMODE_WRITE, &arg->stateid, &delegation_cred)) {
/* Use that stateid */
