ovl: support multiple lower layers
Allow "lowerdir=" option to contain multiple lower directories separated by
a colon (e.g. "lowerdir=/bin:/usr/bin"). Colon characters in filenames can
be escaped with a backslash.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt
index a27c950..b370928 100644
--- a/Documentation/filesystems/overlayfs.txt
+++ b/Documentation/filesystems/overlayfs.txt
@@ -159,6 +159,18 @@
rename or unlink will of course be noticed and handled).
+Multiple lower layers
+---------------------
+
+Multiple lower layers can now be given using the the colon (":") as a
+separator character between the directory names. For example:
+
+ mount -t overlay overlay -olowerdir=/lower1:/lower2:/lower3 /merged
+
+As the example shows, "upperdir=" and "workdir=" may be omitted. In that case
+the overlay will be read-only.
+
+
Non-standard behavior
---------------------