Commit 644c9f40 authored Sep 04, 2020 by Chuck Lever Committed by Trond Myklebust Sep 05, 2020

NFS: Zero-stateid SETATTR should first return delegation



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@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

parent 3d7a9520

fs/nfs/nfs4proc.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -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 */

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