smb3: log warning if CSC policy conflicts with cache mount option

If the server config (e.g. Samba smb.conf "csc policy = disable)
for the share indicates that the share should not be cached, log
a warning message if forced client side caching ("cache=ro" or
"cache=singleclient") is requested on mount.

Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d9a995588c74..85f8d943a05a 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3478,6 +3478,14 @@ cifs_get_tcon(struct cifs_ses *ses, struct smb_vol *volume_info)
                 tcon->use_resilient = true;
         }
 
+        /* If the user really knows what they are doing they can override */
+        if (tcon->share_flags & SMB2_SHAREFLAG_NO_CACHING) {
+                if (volume_info->cache_ro)
+                        cifs_dbg(VFS, "cache=ro requested on mount but NO_CACHING flag set on share\n");
+                else if (volume_info->cache_rw)
+                        cifs_dbg(VFS, "cache=singleclient requested on mount but NO_CACHING flag set on share\n");
+        }
+
         /*
          * We can have only one retry value for a connection to a share so for
          * resources mounted more than once to the same server share the last