Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: [PATCH v4 7/8] NFSD: Make nfsd4_rename() wait before returning
 NFS4ERR_DELAY
From:   Chuck Lever <chuck.lever@oracle.com>
To:     linux-nfs@vger.kernel.org
Date:   Thu, 08 Sep 2022 18:14:19 -0400
Message-ID: <166267525948.1842.17093479396791635591.stgit@manet.1015granger.net>
In-Reply-To: <166267495153.1842.14474564029477470642.stgit@manet.1015granger.net>
References: <166267495153.1842.14474564029477470642.stgit@manet.1015granger.net>
User-Agent: StGit/1.5.dev2+g9ce680a5
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Precedence: bulk

nfsd_rename() can kick off a CB_RECALL (via
vfs_rename() -> leases_conflict()) 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_rename()
again, once.

This version of the patch handles renaming an existing file,
but does not deal with renaming onto an existing file. That
case will still always trigger an NFS4ERR_DELAY.

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 |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 03a826ccc165..b597cb2af949 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1681,7 +1681,15 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 			.new_dir	= tdir,
 			.new_dentry	= ndentry,
 		};
-		host_err = vfs_rename(&rd);
+		int retries;
+
+		for (retries = 1;;) {
+			host_err = vfs_rename(&rd);
+			if (host_err != -EAGAIN || !retries--)
+				break;
+			if (!nfsd_wait_for_delegreturn(rqstp, d_inode(odentry)))
+				break;
+		}
 		if (!host_err) {
 			host_err = commit_metadata(tfhp);
 			if (!host_err)