-stable review patch. If anyone has any objections, please let us know. ------------------ From: Jens Axboe <[EMAIL PROTECTED]>
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 <[EMAIL PROTECTED]> Signed-off-by: Greg Kroah-Hartman <[EMAIL PROTECTED]> --- block/cfq-iosched.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -462,6 +462,12 @@ static void cfq_add_rq_rb(struct request 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, s 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 */ -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
