tree f7b28991b281a8c581bd3ab0bb470e158ae2206f
parent 8e5cfc45e7527eb5c8a9a22d56a7b9227e7c0913
author Jens Axboe <jens.axboe@oracle.com> 1166609052 +0100
committer Jens Axboe <jens.axboe@oracle.com> 1166609052 +0100

[PATCH] cfq-iosched: don't allow sync merges across queues

Currently we allow any merge, even if the io originates from different
processes. This can cause really bad starvation and unfairness, if those
ios happen to be synchronous (reads or direct writes).

So add a allow_merge hook to the io scheduler ops, so an io scheduler can
help decide whether a bio/process combination may be merged with an
existing request.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>