filestore: fix wake condition when journal submission blocks
filestore: fix wake condition when journal submission blocks

We only want to wake up if we are at the front of the line, in order to
preserve journal submission pipeline ordering.

This fixes, among other things, messages in the log like

2010-12-21 10:38:42.515974 7f0861486700 journal op_submit_finish 5364 expected 5370, OUT OF ORDER

and bug #666.

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph