From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk
Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org,
hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org,
vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org,
linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com,
fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com,
Tejun Heo <tj@kernel.org>
Subject: [PATCH 06/48] cgroup, block: implement task_get_css() and use it in bio_associate_current()
Date: Mon, 23 Mar 2015 00:54:17 -0400 [thread overview]
Message-ID: <1427086499-15657-7-git-send-email-tj@kernel.org> (raw)
In-Reply-To: <1427086499-15657-1-git-send-email-tj@kernel.org>
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 <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
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
--
2.1.0
--
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next prev parent reply other threads:[~2015-03-23 4:54 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-23 4:54 [PATCHSET 1/3 v2 block/for-4.1/core] writeback: cgroup writeback support Tejun Heo
2015-03-23 4:54 ` [PATCH 01/48] memcg: add per cgroup dirty page accounting Tejun Heo
2015-03-23 4:54 ` [PATCH 02/48] blkcg: move block/blk-cgroup.h to include/linux/blk-cgroup.h Tejun Heo
2015-03-23 4:54 ` [PATCH 04/48] memcg: add mem_cgroup_root_css Tejun Heo
2015-03-23 4:54 ` [PATCH 05/48] blkcg: add blkcg_root_css Tejun Heo
2015-03-23 4:54 ` Tejun Heo [this message]
2015-03-23 4:54 ` [PATCH 07/48] blkcg: implement task_get_blkcg_css() Tejun Heo
2015-03-23 4:54 ` [PATCH 08/48] blkcg: implement bio_associate_blkcg() Tejun Heo
2015-03-23 4:54 ` [PATCH 09/48] memcg: implement mem_cgroup_css_from_page() Tejun Heo
2015-03-23 4:54 ` [PATCH 10/48] writeback: move backing_dev_info->state into bdi_writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 11/48] writeback: move backing_dev_info->bdi_stat[] " Tejun Heo
2015-03-23 4:54 ` [PATCH 12/48] writeback: move bandwidth related fields from backing_dev_info " Tejun Heo
2015-03-23 4:54 ` [PATCH 13/48] writeback: s/bdi/wb/ in mm/page-writeback.c Tejun Heo
2015-03-23 4:54 ` [PATCH 14/48] writeback: move backing_dev_info->wb_lock and ->worklist into bdi_writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 15/48] writeback: reorganize mm/backing-dev.c Tejun Heo
2015-03-23 4:54 ` [PATCH 16/48] writeback: separate out include/linux/backing-dev-defs.h Tejun Heo
2015-03-23 4:54 ` [PATCH 17/48] bdi: make inode_to_bdi() inline Tejun Heo
2015-03-23 4:54 ` [PATCH 18/48] writeback: add @gfp to wb_init() Tejun Heo
2015-03-23 4:54 ` [PATCH 19/48] bdi: separate out congested state into a separate struct Tejun Heo
2015-03-23 4:54 ` [PATCH 20/48] writeback: add {CONFIG|BDI_CAP|FS}_CGROUP_WRITEBACK Tejun Heo
2015-03-23 4:54 ` [PATCH 21/48] writeback: make backing_dev_info host cgroup-specific bdi_writebacks Tejun Heo
2015-03-27 21:06 ` Vivek Goyal
2015-03-27 21:41 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 22/48] writeback, blkcg: associate each blkcg_gq with the corresponding bdi_writeback_congested Tejun Heo
2015-03-23 4:54 ` [PATCH 24/48] writeback: let balance_dirty_pages() work on the matching cgroup bdi_writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 25/48] writeback: make congestion functions per bdi_writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 26/48] writeback, blkcg: restructure blk_{set|clear}_queue_congested() Tejun Heo
2015-03-23 4:54 ` [PATCH 28/48] writeback: implement and use mapping_congested() Tejun Heo
[not found] ` <1427086499-15657-29-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2015-03-27 18:06 ` Vivek Goyal
2015-03-27 21:46 ` Tejun Heo
2015-03-23 4:54 ` [PATCH 29/48] writeback: implement WB_has_dirty_io wb_state flag Tejun Heo
2015-03-23 4:54 ` [PATCH 30/48] writeback: implement backing_dev_info->tot_write_bandwidth Tejun Heo
2015-03-23 4:54 ` [PATCH 31/48] writeback: make bdi_has_dirty_io() take multiple bdi_writeback's into account Tejun Heo
2015-03-23 4:54 ` [PATCH 32/48] writeback: don't issue wb_writeback_work if clean Tejun Heo
2015-03-23 4:54 ` [PATCH 33/48] writeback: make bdi->min/max_ratio handling cgroup writeback aware Tejun Heo
2015-03-23 4:54 ` [PATCH 34/48] writeback: implement bdi_for_each_wb() Tejun Heo
2015-03-23 4:54 ` [PATCH 35/48] writeback: remove bdi_start_writeback() Tejun Heo
2015-03-23 4:54 ` [PATCH 36/48] writeback: make laptop_mode_timer_fn() handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` [PATCH 37/48] writeback: make writeback_in_progress() take bdi_writeback instead of backing_dev_info Tejun Heo
2015-03-23 4:54 ` [PATCH 38/48] writeback: make bdi_start_background_writeback() " Tejun Heo
2015-03-23 4:54 ` [PATCH 39/48] writeback: make wakeup_flusher_threads() handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` [PATCH 40/48] writeback: add wb_writeback_work->auto_free Tejun Heo
2015-03-23 4:54 ` [PATCH 41/48] writeback: implement bdi_wait_for_completion() Tejun Heo
2015-03-23 4:54 ` [PATCH 42/48] writeback: implement wb_wait_for_single_work() Tejun Heo
2015-03-23 4:54 ` [PATCH 44/48] writeback: make writeback initiation functions handle multiple bdi_writeback's Tejun Heo
2015-03-23 4:54 ` [PATCH 45/48] writeback: dirty inodes against their matching cgroup bdi_writeback's Tejun Heo
2015-03-23 4:54 ` [PATCH 46/48] buffer, writeback: make __block_write_full_page() honor cgroup writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 47/48] mpage: make __mpage_writepage() " Tejun Heo
2015-03-23 4:54 ` [PATCH 48/48] ext2: enable cgroup writeback support Tejun Heo
[not found] ` <1427086499-15657-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2015-03-23 4:54 ` [PATCH 03/48] update !CONFIG_BLK_CGROUP dummies in include/linux/blk-cgroup.h Tejun Heo
2015-03-23 4:54 ` [PATCH 23/48] writeback: attribute stats to the matching per-cgroup bdi_writeback Tejun Heo
2015-03-23 4:54 ` [PATCH 27/48] writeback, blkcg: propagate non-root blkcg congestion state Tejun Heo
2015-03-23 4:54 ` [PATCH 43/48] writeback: restructure try_writeback_inodes_sb[_nr]() Tejun Heo
2015-03-25 15:40 ` [PATCHSET 1/3 v2 block/for-4.1/core] writeback: cgroup writeback support Vivek Goyal
[not found] ` <20150325154022.GC29728-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2015-03-25 16:01 ` Tejun Heo
2015-03-31 15:26 ` Tejun Heo
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