From d4478e92d6186ce37947a36994de407c27446266 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Mon, 25 Sep 2017 13:07:22 -0600 Subject: block/loop: make loop cgroup aware loop block device handles IO in a separate thread. The actual IO dispatched isn't cloned from the IO loop device received, so the dispatched IO loses the cgroup context. I'm ignoring buffer IO case now, which is quite complicated. Making the loop thread aware cgroup context doesn't really help. The loop device only writes to a single file. In current writeback cgroup implementation, the file can only belong to one cgroup. For direct IO case, we could workaround the issue in theory. For example, say we assign cgroup1 5M/s BW for loop device and cgroup2 10M/s. We can create a special cgroup for loop thread and assign at least 15M/s for the underlayer disk. In this way, we correctly throttle the two cgroups. But this is tricky to setup. This patch tries to address the issue. We record bio's css in loop command. When loop thread is handling the command, we then use the API provided in patch 1 to set the css for current task. The bio layer will use the css for new IO (from patch 3). Acked-by: Tejun Heo Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- drivers/block/loop.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'drivers/block/loop.c') diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 85de67334695..fd4eff5f5b76 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -476,6 +476,8 @@ static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2) { struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb); + if (cmd->css) + css_put(cmd->css); cmd->ret = ret; lo_rw_aio_do_completion(cmd); } @@ -535,6 +537,8 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, cmd->iocb.ki_filp = file; cmd->iocb.ki_complete = lo_rw_aio_complete; cmd->iocb.ki_flags = IOCB_DIRECT; + if (cmd->css) + kthread_associate_blkcg(cmd->css); if (rw == WRITE) ret = call_write_iter(file, &cmd->iocb, &iter); @@ -542,6 +546,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, ret = call_read_iter(file, &cmd->iocb, &iter); lo_rw_aio_do_completion(cmd); + kthread_associate_blkcg(NULL); if (ret != -EIOCBQUEUED) cmd->iocb.ki_complete(&cmd->iocb, ret, 0); @@ -1686,6 +1691,14 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, break; } + /* always use the first bio's css */ +#ifdef CONFIG_CGROUPS + if (cmd->use_aio && cmd->rq->bio && cmd->rq->bio->bi_css) { + cmd->css = cmd->rq->bio->bi_css; + css_get(cmd->css); + } else +#endif + cmd->css = NULL; kthread_queue_work(&lo->worker, &cmd->work); return BLK_STS_OK; -- cgit v1.3-8-gc7d7 From 0b508bc926bdced678febee2a2b8cdba0a19e481 Mon Sep 17 00:00:00 2001 From: Shaohua Li Date: Tue, 26 Sep 2017 11:02:12 -0700 Subject: block: fix a build error The code is only for blkcg not for all cgroups Fixes: d4478e92d618 ("block/loop: make loop cgroup aware") Reported-by: kbuild test robot Signed-off-by: Shaohua Li Signed-off-by: Jens Axboe --- drivers/block/loop.c | 2 +- include/linux/kthread.h | 2 +- kernel/kthread.c | 8 ++++---- 3 files changed, 6 insertions(+), 6 deletions(-) (limited to 'drivers/block/loop.c') diff --git a/drivers/block/loop.c b/drivers/block/loop.c index fd4eff5f5b76..bc8e61506968 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1692,7 +1692,7 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, } /* always use the first bio's css */ -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP if (cmd->use_aio && cmd->rq->bio && cmd->rq->bio->bi_css) { cmd->css = cmd->rq->bio->bi_css; css_get(cmd->css); diff --git a/include/linux/kthread.h b/include/linux/kthread.h index bd4369c83dfb..fb201842c635 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -199,7 +199,7 @@ bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work); void kthread_destroy_worker(struct kthread_worker *worker); -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP void kthread_associate_blkcg(struct cgroup_subsys_state *css); struct cgroup_subsys_state *kthread_blkcg(void); #else diff --git a/kernel/kthread.c b/kernel/kthread.c index b011ea08967f..f87cd8b4eb2a 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -46,7 +46,7 @@ struct kthread { void *data; struct completion parked; struct completion exited; -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP struct cgroup_subsys_state *blkcg_css; #endif }; @@ -83,7 +83,7 @@ void free_kthread_struct(struct task_struct *k) * or if kmalloc() in kthread() failed. */ kthread = to_kthread(k); -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP WARN_ON_ONCE(kthread && kthread->blkcg_css); #endif kfree(kthread); @@ -224,7 +224,7 @@ static int kthread(void *_create) self->data = data; init_completion(&self->exited); init_completion(&self->parked); -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP self->blkcg_css = NULL; #endif current->vfork_done = &self->exited; @@ -1166,7 +1166,7 @@ void kthread_destroy_worker(struct kthread_worker *worker) } EXPORT_SYMBOL(kthread_destroy_worker); -#ifdef CONFIG_CGROUPS +#ifdef CONFIG_BLK_CGROUP /** * kthread_associate_blkcg - associate blkcg to current kthread * @css: the cgroup info -- cgit v1.3-8-gc7d7