From f469a7b4d5b1d1d053200a9015fd25d59c057f49 Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Thu, 19 May 2011 15:38:23 -0400 Subject: blk-cgroup: Allow sleeping while dynamically allocating a group Currently, all the cfq_group or throtl_group allocations happen while we are holding ->queue_lock and sleeping is not allowed. Soon, we will move to per cpu stats and also need to allocate the per group stats. As one can not call alloc_percpu() from atomic context as it can sleep, we need to drop ->queue_lock, allocate the group, retake the lock and continue processing. In throttling code, I check the queue DEAD flag again to make sure that driver did not call blk_cleanup_queue() in the mean time. Signed-off-by: Vivek Goyal Signed-off-by: Jens Axboe --- block/blk-throttle.c | 141 +++++++++++++++++++++++++++++++++++++++------------ 1 file changed, 108 insertions(+), 33 deletions(-) (limited to 'block/blk-throttle.c') diff --git a/block/blk-throttle.c b/block/blk-throttle.c index fa9a900c125..c201967b33c 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -188,20 +188,46 @@ throtl_add_group_to_td_list(struct throtl_data *td, struct throtl_grp *tg) td->nr_undestroyed_grps++; } -static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td, - struct blkio_cgroup *blkcg) +static void throtl_init_add_tg_lists(struct throtl_data *td, + struct throtl_grp *tg, struct blkio_cgroup *blkcg) +{ + struct backing_dev_info *bdi = &td->queue->backing_dev_info; + unsigned int major, minor; + + /* Add group onto cgroup list */ + sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); + blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, + MKDEV(major, minor), BLKIO_POLICY_THROTL); + + tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev); + tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev); + tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev); + tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev); + + throtl_add_group_to_td_list(td, tg); +} + +/* Should be called without queue lock and outside of rcu period */ +static struct throtl_grp *throtl_alloc_tg(struct throtl_data *td) +{ + struct throtl_grp *tg = NULL; + + tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); + if (!tg) + return NULL; + + throtl_init_group(tg); + return tg; +} + +static struct +throtl_grp *throtl_find_tg(struct throtl_data *td, struct blkio_cgroup *blkcg) { struct throtl_grp *tg = NULL; void *key = td; struct backing_dev_info *bdi = &td->queue->backing_dev_info; unsigned int major, minor; - /* - * TODO: Speed up blkiocg_lookup_group() by maintaining a radix - * tree of blkg (instead of traversing through hash list all - * the time. - */ - /* * This is the common case when there are no blkio cgroups. * Avoid lookup in this case @@ -215,43 +241,83 @@ static struct throtl_grp * throtl_find_alloc_tg(struct throtl_data *td, if (tg && !tg->blkg.dev && bdi->dev && dev_name(bdi->dev)) { sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); tg->blkg.dev = MKDEV(major, minor); - goto done; } - if (tg) - goto done; - - tg = kzalloc_node(sizeof(*tg), GFP_ATOMIC, td->queue->node); - if (!tg) - goto done; - - throtl_init_group(tg); - - /* Add group onto cgroup list */ - sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor); - blkiocg_add_blkio_group(blkcg, &tg->blkg, (void *)td, - MKDEV(major, minor), BLKIO_POLICY_THROTL); - - tg->bps[READ] = blkcg_get_read_bps(blkcg, tg->blkg.dev); - tg->bps[WRITE] = blkcg_get_write_bps(blkcg, tg->blkg.dev); - tg->iops[READ] = blkcg_get_read_iops(blkcg, tg->blkg.dev); - tg->iops[WRITE] = blkcg_get_write_iops(blkcg, tg->blkg.dev); - - throtl_add_group_to_td_list(td, tg); -done: return tg; } +/* + * This function returns with queue lock unlocked in case of error, like + * request queue is no more + */ static struct throtl_grp * throtl_get_tg(struct throtl_data *td) { - struct throtl_grp *tg = NULL; + struct throtl_grp *tg = NULL, *__tg = NULL; struct blkio_cgroup *blkcg; + struct request_queue *q = td->queue; rcu_read_lock(); blkcg = task_blkio_cgroup(current); - tg = throtl_find_alloc_tg(td, blkcg); - if (!tg) + tg = throtl_find_tg(td, blkcg); + if (tg) { + rcu_read_unlock(); + return tg; + } + + /* + * Need to allocate a group. Allocation of group also needs allocation + * of per cpu stats which in-turn takes a mutex() and can block. Hence + * we need to drop rcu lock and queue_lock before we call alloc + * + * Take the request queue reference to make sure queue does not + * go away once we return from allocation. + */ + blk_get_queue(q); + rcu_read_unlock(); + spin_unlock_irq(q->queue_lock); + + tg = throtl_alloc_tg(td); + /* + * We might have slept in group allocation. Make sure queue is not + * dead + */ + if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { + blk_put_queue(q); + if (tg) + kfree(tg); + + return ERR_PTR(-ENODEV); + } + blk_put_queue(q); + + /* Group allocated and queue is still alive. take the lock */ + spin_lock_irq(q->queue_lock); + + /* + * Initialize the new group. After sleeping, read the blkcg again. + */ + rcu_read_lock(); + blkcg = task_blkio_cgroup(current); + + /* + * If some other thread already allocated the group while we were + * not holding queue lock, free up the group + */ + __tg = throtl_find_tg(td, blkcg); + + if (__tg) { + kfree(tg); + rcu_read_unlock(); + return __tg; + } + + /* Group allocation failed. Account the IO to root group */ + if (!tg) { tg = &td->root_tg; + return tg; + } + + throtl_init_add_tg_lists(td, tg, blkcg); rcu_read_unlock(); return tg; } @@ -1014,6 +1080,15 @@ int blk_throtl_bio(struct request_queue *q, struct bio **biop) spin_lock_irq(q->queue_lock); tg = throtl_get_tg(td); + if (IS_ERR(tg)) { + if (PTR_ERR(tg) == -ENODEV) { + /* + * Queue is gone. No queue lock held here. + */ + return -ENODEV; + } + } + if (tg->nr_queued[rw]) { /* * There is already another bio queued in same dir. No -- cgit v1.2.3-18-g5258