CRED: Wrap task credential accesses in the FUSE filesystem

Wrap access to task credentials so that they can be separated more easily from
the task_struct during the introduction of COW creds.

Change most current->(|e|s|fs)[ug]id to current_(|e|s|fs)[ug]id().

Change some task->e?[ug]id to task_e?[ug]id().  In some places it makes more
sense to use RCU directly rather than a convenient wrapper; these will be
addressed by later patches.

Signed-off-by: David Howells <[email protected]>
Reviewed-by: James Morris <[email protected]>
Acked-by: Serge Hallyn <[email protected]>
Cc: Miklos Szeredi <[email protected]>
Cc: [email protected]
Signed-off-by: James Morris <[email protected]>

fs/fuse/dev.c

@@ -87,8 +87,8 @@ static void __fuse_put_request(struct fuse_req *req)
 
 static void fuse_req_init_context(struct fuse_req *req)
 {
-	req->in.h.uid = current->fsuid;
-	req->in.h.gid = current->fsgid;
+	req->in.h.uid = current_fsuid();
+	req->in.h.gid = current_fsgid();
 	req->in.h.pid = current->pid;
 }