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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>
zero-sugar-mainline-defconfig
Chuck Lever 2020-09-04 17:39:12 -04:00 committed by Trond Myklebust
parent 3d7a9520f0
commit 644c9f40cf
1 changed files with 3 additions and 1 deletions
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4
fs/nfs/nfs4proc.c
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@ -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 */