[PATCH 1/3] NFS: Disable READ_PLUS by default

[schumaker.anna@gmail.com]

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

We've been seeing failures with xfstests generic/091 and generic/263
when using READ_PLUS. I've made some progress on these issues, and the
tests fail later on but still don't pass. Let's disable READ_PLUS by
default until we can work out what is going on.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfs/Kconfig    | 9 +++++++++
 fs/nfs/nfs4proc.c | 2 +-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
index 88e1763e02f3..e2a488d403a6 100644
--- a/fs/nfs/Kconfig
+++ b/fs/nfs/Kconfig
@@ -205,3 +205,12 @@ config NFS_DISABLE_UDP_SUPPORT
 	 Choose Y here to disable the use of NFS over UDP. NFS over UDP
 	 on modern networks (1Gb+) can lead to data corruption caused by
 	 fragmentation during high loads.
+
+config NFS_V4_2_READ_PLUS
+	bool "NFS: Enable support for the NFSv4.2 READ_PLUS operation"
+	depends on NFS_V4_2
+	default n
+	help
+	 This is intended for developers only. The READ_PLUS operation has
+	 been shown to have issues under specific conditions and should not
+	 be used in production.
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 9e0ca9b2b210..e89468678ae1 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5309,7 +5309,7 @@ static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 				    nfs4_read_done_cb(task, hdr);
 }
 
-#ifdef CONFIG_NFS_V4_2
+#if defined CONFIG_NFS_V4_2 && defined CONFIG_NFS_V4_2_READ_PLUS
 static void nfs42_read_plus_support(struct nfs_server *server, struct rpc_message *msg)
 {
 	if (server->caps & NFS_CAP_READ_PLUS)
-- 
2.29.2