1 files changed, 25 insertions, 3 deletions

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 6e29954851a2..b4a3d765ff9a 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -400,10 +400,32 @@ a file off.
 
 --
 [mandatory]
-
---
-[mandatory]
         ->get_sb() is gone.  Switch to use of ->mount().  Typically it's just
 a matter of switching from calling get_sb_... to mount_... and changing the
 function type.  If you were doing it manually, just switch from setting ->mnt_root
 to some pointer to returning that pointer.  On errors return ERR_PTR(...).
+
+--
+[mandatory]
+        ->permission() and generic_permission()have lost flags
+argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask.
+        generic_permission() has also lost the check_acl argument; ACL checking
+has been taken to VFS and filesystems need to provide a non-NULL ->i_op->get_acl
+to read an ACL from disk.
+
+--
+[mandatory]
+        If you implement your own ->llseek() you must handle SEEK_HOLE and
+SEEK_DATA.  You can hanle this by returning -EINVAL, but it would be nicer to
+support it in some way.  The generic handler assumes that the entire file is
+data and there is a virtual hole at the end of the file.  So if the provided
+offset is less than i_size and SEEK_DATA is specified, return the same offset.
+If the above is true for the offset and you are given SEEK_HOLE, return the end
+of the file.  If the offset is i_size or greater return -ENXIO in either case.
+
+[mandatory]
+        If you have your own ->fsync() you must make sure to call
+filemap_write_and_wait_range() so that all dirty pages are synced out properly.
+You must also keep in mind that ->fsync() is not called with i_mutex held
+anymore, so if you require i_mutex locking you must make sure to take it and
+release it yourself.