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-rw-r--r--Documentation/filesystems/porting10
1 files changed, 10 insertions, 0 deletions
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 0eeb3954dea..6b96773e27c 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -411,3 +411,13 @@ 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.