Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934378AbbEPEO3 (ORCPT ); Sat, 16 May 2015 00:14:29 -0400 Received: from mail-wi0-f174.google.com ([209.85.212.174]:36812 "EHLO mail-wi0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934005AbbEPEOY (ORCPT ); Sat, 16 May 2015 00:14:24 -0400 From: Aleksa Sarai To: tj@kernel.org, lizefan@huawei.com, mingo@redhat.com, peterz@infradead.org Cc: richard@nod.at, fweisbec@gmail.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Jens Axboe , Vivek Goyal Subject: [PATCH v11 4/7] cgroup, block: implement task_get_css() and use it in bio_associate_current() Date: Sat, 16 May 2015 14:13:38 +1000 Message-Id: <1431749621-30451-5-git-send-email-cyphar@cyphar.com> X-Mailer: git-send-email 2.4.1 In-Reply-To: <1431749621-30451-1-git-send-email-cyphar@cyphar.com> References: <1431749621-30451-1-git-send-email-cyphar@cyphar.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2794 Lines: 95 From: Tejun Heo bio_associate_current() currently open codes task_css() and css_tryget_online() to find and pin $current's blkcg css. Abstract it into task_get_css() which is implemented from cgroup side. As a task is always associated with an online css for every subsystem except while the css_set update is propagating, task_get_css() retries till css_tryget_online() succeeds. This is a cleanup and shouldn't lead to noticeable behavior changes. Signed-off-by: Tejun Heo Cc: Li Zefan Cc: Jens Axboe Cc: Vivek Goyal --- block/bio.c | 11 +---------- include/linux/cgroup.h | 25 +++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 10 deletions(-) diff --git a/block/bio.c b/block/bio.c index f66a4ea..968683e 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1987,7 +1987,6 @@ EXPORT_SYMBOL(bioset_create_nobvec); int bio_associate_current(struct bio *bio) { struct io_context *ioc; - struct cgroup_subsys_state *css; if (bio->bi_ioc) return -EBUSY; @@ -1996,17 +1995,9 @@ int bio_associate_current(struct bio *bio) if (!ioc) return -ENOENT; - /* acquire active ref on @ioc and associate */ get_io_context_active(ioc); bio->bi_ioc = ioc; - - /* associate blkcg if exists */ - rcu_read_lock(); - css = task_css(current, blkio_cgrp_id); - if (css && css_tryget_online(css)) - bio->bi_css = css; - rcu_read_unlock(); - + bio->bi_css = task_get_css(current, blkio_cgrp_id); return 0; } diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index b9cb94c..e7da0aa 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -774,6 +774,31 @@ static inline struct cgroup_subsys_state *task_css(struct task_struct *task, } /** + * task_get_css - find and get the css for (task, subsys) + * @task: the target task + * @subsys_id: the target subsystem ID + * + * Find the css for the (@task, @subsys_id) combination, increment a + * reference on and return it. This function is guaranteed to return a + * valid css. + */ +static inline struct cgroup_subsys_state * +task_get_css(struct task_struct *task, int subsys_id) +{ + struct cgroup_subsys_state *css; + + rcu_read_lock(); + while (true) { + css = task_css(task, subsys_id); + if (likely(css_tryget_online(css))) + break; + cpu_relax(); + } + rcu_read_unlock(); + return css; +} + +/** * task_css_is_root - test whether a task belongs to the root css * @task: the target task * @subsys_id: the target subsystem ID -- 2.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/