Hi Jens,
This RFC DRAFT patch is on top of your "[PATCH v2] Support for write stream IDs"
I throw it out early to get comments if it's the way to go.
Quote LWN(http://lwn.net/Articles/638722):
"There would be clear value in a closer association between stream IDs
and specific buffered-write operations. Getting there would require storing
the stream ID with each dirtied page, though; that, in turn, almost certainly
implies shoehorning the stream ID into the associated page structure.
That would not be an easy task; it is not surprising that it is not a part of
this patch set. Should the lack of per-buffered-write stream IDs prove to be
a serious constraint in the future, somebody will certainly be motivated to
try to find a place to store another eight bits in struct page."
This draft patch stores stream_id in buffer head instead of page.