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Subject: [PATCH v4 6/8] NFSD: Make nfsd4_setattr() wait before returning
 NFS4ERR_DELAY
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Date:   Thu, 08 Sep 2022 18:14:13 -0400
Message-ID: <166267525333.1842.10708885965116635193.stgit@manet.1015granger.net>
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References: <166267495153.1842.14474564029477470642.stgit@manet.1015granger.net>
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nfsd_setattr() can kick off a CB_RECALL (via
notify_change() -> break_lease()) if a delegation is present. Before
returning NFS4ERR_DELAY, give the client holding that delegation a
chance to return it and then retry the nfsd_setattr() again, once.

Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=354
Tested-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/vfs.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 02f31d8c727a..03a826ccc165 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -394,6 +394,7 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	int		host_err;
 	bool		get_write_count;
 	bool		size_change = (iap->ia_valid & ATTR_SIZE);
+	int		retries;
 
 	if (iap->ia_valid & ATTR_SIZE) {
 		accmode |= NFSD_MAY_WRITE|NFSD_MAY_OWNER_OVERRIDE;
@@ -455,7 +456,13 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp,
 	}
 
 	inode_lock(inode);
-	host_err = __nfsd_setattr(dentry, iap);
+	for (retries = 1;;) {
+		host_err = __nfsd_setattr(dentry, iap);
+		if (host_err != -EAGAIN || !retries--)
+			break;
+		if (!nfsd_wait_for_delegreturn(rqstp, inode))
+			break;
+	}
 	if (attr->na_seclabel && attr->na_seclabel->len)
 		attr->na_labelerr = security_inode_setsecctx(dentry,
 			attr->na_seclabel->data, attr->na_seclabel->len);