Vivek Goyal wrote:

quoted

This patch series seems to be working for me. I did testing for ext4 only.
This series is based on for-3.1/core branch of Jen's block tree.
Konstantin, can you please give it a try and see if it fixes your
issue.

It works for me too, for ext3 and ext4, on top 3.0-rc5, after these trivial fixes:

--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c

@@ -1511,7 +1519,7 @@ static void cfq_add_rq_rb(struct request *rq)
         * if that happens, put the alias on the dispatch list
         */
        while ((__alias = elv_rb_add(&cfqq->sort_list, rq)) != NULL)
-               cfq_dispatch_insert(cfqd->queue, __alias);
+               cfq_dispatch_insert(cfqd->queue, __alias, false);

        if (!cfq_cfqq_on_rr(cfqq))
                cfq_add_cfqq_rr(cfqd, cfqq);

@@ -3797,12 +3797,11 @@ cfq_set_depends_on_task(struct request_queue *q, struct task_struct *tsk)
         */
        rcu_read_lock();
        if (task_blkio_cgroup(current) == task_blkio_cgroup(tsk))
-               return;
-       rcu_read_unlock();
+               goto out_unlock_rcu;

        cic = cfq_cic_lookup(cfqd, current->io_context);
        if (!cic)
-               return;
+               goto out_unlock_rcu;