From 03aa264ac15637b6f98374270bcdf31400965505 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 5 Mar 2012 13:15:19 -0800 Subject: blkcg: let blkcg core manage per-queue blkg list and counter With the previous patch to move blkg list heads and counters to request_queue and blkg, logic to manage them in both policies are almost identical and can be moved to blkcg core. This patch moves blkg link logic into blkg_lookup_create(), implements common blkg unlink code in blkg_destroy(), and updates blkg_destory_all() so that it's policy specific and can skip root group. The updated blkg_destroy_all() is now used to both clear queue for bypassing and elv switching, and release all blkgs on q exit. This patch introduces a race window where policy [de]registration may race against queue blkg clearing. This can only be a problem on cfq unload and shouldn't be a real problem in practice (and we have many other places where this race already exists). Future patches will remove these unlikely races. Signed-off-by: Tejun Heo Cc: Vivek Goyal Signed-off-by: Jens Axboe --- block/elevator.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'block/elevator.c') diff --git a/block/elevator.c b/block/elevator.c index 8c7561fd2c79..d4d39dab841a 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -876,7 +876,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) { struct elevator_queue *old = q->elevator; bool registered = old->registered; - int err; + int i, err; /* * Turn on BYPASS and drain all requests w/ elevator private data. @@ -895,7 +895,8 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e) ioc_clear_queue(q); spin_unlock_irq(q->queue_lock); - blkg_destroy_all(q); + for (i = 0; i < BLKIO_NR_POLICIES; i++) + blkg_destroy_all(q, i, false); /* allocate, init and register new elevator */ err = -ENOMEM; -- cgit v1.2.3