fuse: add request extension

Will need to add supplementary groups to create messages, so add the
general concept of a request extension.  A request extension is appended to
the end of the main request.  It has a header indicating the size and type
of the extension.

The create security context (fuse_secctx_*) is similar to the generic
request extension, so include that as well in a backward compatible manner.

Add the total extension length to the request header.  The offset of the
extension block within the request can be calculated by:

  inh->len - inh->total_extlen * 8

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index e8b60ce72c9a..9f349f834977 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -476,6 +476,8 @@ static void fuse_args_to_req(struct fuse_req *req, struct fuse_args *args)
 	req->in.h.opcode = args->opcode;
 	req->in.h.nodeid = args->nodeid;
 	req->args = args;
+	if (args->is_ext)
+		req->in.h.total_extlen = args->in_args[args->ext_idx].size / 8;
 	if (args->end)
 		__set_bit(FR_ASYNC, &req->flags);
 }