diff options
| author | Jens Axboe <jens.axboe@oracle.com> | 2007-04-25 13:42:27 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2007-05-01 17:06:03 -0700 |
| commit | 3720eda544ece8fa5ade8c87e5f2cf2fb05b0ff5 (patch) | |
| tree | ffd078d3143437b00350f78920df108b0490a32e | |
| parent | ab02a65798ea8b940ea5645655238c778d4e4765 (diff) | |
cfq-iosched: fix alias + front merge bug
There's a really rare and obscure bug in CFQ, that causes a crash in
cfq_dispatch_insert() due to rq == NULL. One example of that is seen
here:
http://lkml.org/lkml/2007/4/15/41
Neil correctly diagnosed the situation for how this can happen, read
that analysis here:
http://lkml.org/lkml/2007/4/25/57
This looks like it requires md to trigger, even though it should
potentially be possible to due with O_DIRECT (at least if you edit the
kernel and doctor some of the unplug calls).
The fix is to move the ->next_rq update to when we add a request to the
rbtree. Then we remove the possibility for a request to exist in the
rbtree code, but not have ->next_rq correctly updated.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | block/cfq-iosched.c | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 07b70624377..0280fe661cd 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -462,6 +462,12 @@ static void cfq_add_rq_rb(struct request *rq) if (!cfq_cfqq_on_rr(cfqq)) cfq_add_cfqq_rr(cfqd, cfqq); + + /* + * check if this request is a better next-serve candidate + */ + cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); + BUG_ON(!cfqq->next_rq); } static inline void @@ -1623,12 +1629,6 @@ cfq_rq_enqueued(struct cfq_data *cfqd, struct cfq_queue *cfqq, cfqq->meta_pending++; /* - * check if this request is a better next-serve candidate)) { - */ - cfqq->next_rq = cfq_choose_req(cfqd, cfqq->next_rq, rq); - BUG_ON(!cfqq->next_rq); - - /* * we never wait for an async request and we don't allow preemption * of an async request. so just return early */ |