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Subject: [PATCH v1] NFS: Zero-stateid SETATTR should first return delegation
From:   Chuck Lever <chuck.lever@oracle.com>
To:     trondmy@hammerspace.com, anna.schumaker@netapp.com
Cc:     linux-nfs@vger.kernel.org
Date:   Fri, 28 Aug 2020 15:58:25 -0400
Message-ID: <159864470513.1031951.14868951913532221090.stgit@manet.1015granger.net>
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If a write delegation isn't available, the Linux NFS client uses
a zero-stateid when performing a SETATTR.

If that client happens to hold a read delegation, the server will
recall it immediately, resulting in a short delay while the
CB_RECALL operation is done. Optimize out this delay by having the
client return any delegation it may hold on a file before issuing a
SETATTR(zero-stateid) on that file.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfs/nfs4proc.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index dbd01548335b..53a56250cf4b 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -3314,6 +3314,7 @@ static int _nfs4_do_setattr(struct inode *inode,
 			goto zero_stateid;
 	} else {
 zero_stateid:
+		nfs4_inode_return_delegation(inode);
 		nfs4_stateid_copy(&arg->stateid, &zero_stateid);
 	}
 	if (delegation_cred)