From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Sat, 3 Aug 2019 13:39:24 -0400
Subject: [PATCH] NFS: Fix regression whereby fscache errors are appearing on
 'nofsc' mounts
Git-commit: dea1bb35c5f35e0577cfc61f79261d80b8715221
Patch-mainline: v5.3
References: git-fixes

People are reporing seeing fscache errors being reported concerning
duplicate cookies even in cases where they are not setting up fscache
at all. The rule needs to be that if fscache is not enabled, then it
should have no side effects at all.

To ensure this is the case, we disable fscache completely on all superblocks
for which the 'fsc' mount option was not set. In order to avoid issues
with '-oremount', we also disable the ability to turn fscache on via
remount.

Fixes: f1fe29b4a02d ("NFS: Use i_writecount to control whether...")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=200145
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Cc: Steve Dickson <steved@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/fscache.c |    7 ++++++-
 fs/nfs/fscache.h |    2 +-
 fs/nfs/super.c   |    1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -71,6 +71,10 @@ void nfs_fscache_get_super_cookie(struct
 	struct rb_node **p, *parent;
 	int diff;
 
+	nfss->fscache_key = NULL;
+	nfss->fscache = NULL;
+	if (!(nfss->options & NFS_OPTION_FSCACHE))
+		return;
 	if (!uniq) {
 		uniq = "";
 		ulen = 1;
@@ -180,10 +184,11 @@ void nfs_fscache_release_super_cookie(st
  */
 void nfs_fscache_init_inode(struct inode *inode)
 {
+	struct nfs_server *nfss = NFS_SERVER(inode);
 	struct nfs_inode *nfsi = NFS_I(inode);
 
 	nfsi->fscache = NULL;
-	if (!S_ISREG(inode->i_mode))
+	if (!(nfss->fscache && S_ISREG(inode->i_mode)))
 		return;
 	nfsi->fscache = fscache_acquire_cookie(NFS_SB(inode->i_sb)->fscache,
 					       &nfs_fscache_inode_object_def,
--- a/fs/nfs/fscache.h
+++ b/fs/nfs/fscache.h
@@ -171,7 +171,7 @@ static inline void nfs_fscache_wait_on_i
  */
 static inline const char *nfs_server_fscache_state(struct nfs_server *server)
 {
-	if (server->fscache && (server->options & NFS_OPTION_FSCACHE))
+	if (server->fscache)
 		return "yes";
 	return "no ";
 }
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2250,6 +2250,7 @@ nfs_compare_remount_data(struct nfs_serv
 	    data->acdirmin != nfss->acdirmin / HZ ||
 	    data->acdirmax != nfss->acdirmax / HZ ||
 	    data->timeo != (10U * nfss->client->cl_timeout->to_initval / HZ) ||
+	    (data->options & NFS_OPTION_FSCACHE) != (nfss->options & NFS_OPTION_FSCACHE) ||
 	    data->nfs_server.port != nfss->port ||
 	    data->nfs_server.addrlen != nfss->nfs_client->cl_addrlen ||
 	    !rpc_cmp_addr((struct sockaddr *)&data->nfs_server.address,