1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 1eb76959d096..ccf0ce7866b9 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -346,3 +346,17 @@ look at examples of other filesystems) for guidance.
 for details of what locks to replace dcache_lock with in order to protect
 particular things. Most of the time, a filesystem only needs ->d_lock, which
 protects *all* the dcache state of a given dentry.
+
+--
+[mandatory]
+
+        Filesystems must RCU-free their inodes, if they can have been accessed
+via rcu-walk path walk (basically, if the file can have had a path name in the
+vfs namespace).
+
+        i_dentry and i_rcu share storage in a union, and the vfs expects
+i_dentry to be reinitialized before it is freed, so an:
+
+  INIT_LIST_HEAD(&inode->i_dentry);
+
+must be done in the RCU callback.