ovl: update Kconfig texts

Add some hints about overlayfs kernel config options.

Enabling NFS export by default is especially recommended against, as it
incurs a performance penalty even if the filesystem is not actually
exported.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 406e72de88f6..ce6ff5a0a6e4 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -24,6 +24,8 @@ config OVERLAY_FS_REDIRECT_DIR
           an overlay which has redirects on a kernel that doesn't support this
           feature will have unexpected results.
 
+          If unsure, say N.
+
 config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
         bool "Overlayfs: follow redirects even if redirects are turned off"
         default y
@@ -32,8 +34,13 @@ config OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW
           Disable this to get a possibly more secure configuration, but that
           might not be backward compatible with previous kernels.
 
+          If backward compatibility is not an issue, then it is safe and
+          recommended to say N here.
+
           For more information, see Documentation/filesystems/overlayfs.txt
 
+          If unsure, say Y.
+
 config OVERLAY_FS_INDEX
         bool "Overlayfs: turn on inodes index feature by default"
         depends on OVERLAY_FS
@@ -51,6 +58,8 @@ config OVERLAY_FS_INDEX
           That is, mounting an overlay which has an inodes index on a kernel
           that doesn't support this feature will have unexpected results.
 
+          If unsure, say N.
+
 config OVERLAY_FS_NFS_EXPORT
         bool "Overlayfs: turn on NFS export feature by default"
         depends on OVERLAY_FS
@@ -72,3 +81,8 @@ config OVERLAY_FS_NFS_EXPORT
           Note, that the NFS export feature is not backward compatible.
           That is, mounting an overlay which has a full index on a kernel
           that doesn't support this feature will have unexpected results.
+
+          Most users should say N here and enable this feature on a case-by-
+          case basis with the "nfs_export=on" mount option.
+
+          Say N unless you fully understand the consequences.