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-rw-r--r--fs/overlayfs/Kconfig31
1 files changed, 25 insertions, 6 deletions
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 5ac415466861..406e72de88f6 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -47,9 +47,28 @@ config OVERLAY_FS_INDEX
The inodes index feature prevents breaking of lower hardlinks on copy
up.
- Note, that the inodes index feature is read-only backward compatible.
- That is, mounting an overlay which has an index dir on a kernel that
- doesn't support this feature read-only, will not have any negative
- outcomes. However, mounting the same overlay with an old kernel
- read-write and then mounting it again with a new kernel, will have
- unexpected results.
+ Note, that the inodes index feature is not backward compatible.
+ That is, mounting an overlay which has an inodes index on a kernel
+ that doesn't support this feature will have unexpected results.
+
+config OVERLAY_FS_NFS_EXPORT
+ bool "Overlayfs: turn on NFS export feature by default"
+ depends on OVERLAY_FS
+ depends on OVERLAY_FS_INDEX
+ help
+ If this config option is enabled then overlay filesystems will use
+ the inodes index dir to decode overlay NFS file handles by default.
+ In this case, it is still possible to turn off NFS export support
+ globally with the "nfs_export=off" module option or on a filesystem
+ instance basis with the "nfs_export=off" mount option.
+
+ The NFS export feature creates an index on copy up of every file and
+ directory. This full index is used to detect overlay filesystems
+ inconsistencies on lookup, like redirect from multiple upper dirs to
+ the same lower dir. The full index may incur some overhead on mount
+ time, especially when verifying that directory file handles are not
+ stale.
+
+ 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.