fs/epoll: deal with wait_queue only once

fs/epoll: deal with wait_queue only once

There is no reason why we rearm the waitiqueue upon every fetch_events
retry (for when events are found yet send_events() fails).  If nothing
else, this saves four lock operations per retry, and furthermore reduces
the scope of the lock even further.

[[email protected]: restore code to original position, fix and reflow comment]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Davidlohr Bueso <[email protected]>
Cc: Jason Baron <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>