Merge branch 'for-upstream' of git://openrisc.net/jonas/linux

[pandora-kernel.git] / Documentation / filesystems / porting

diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 0eeb395..7f8861d 100644 (file)
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -411,3 +411,20 @@ to some pointer to returning that pointer.  On errors return ERR_PTR(...).
 argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask.
        generic_permission() has also lost the check_acl argument; if you want
 non-NULL to be used for that inode, put it into ->i_op->check_acl.
+
+--
+[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.