On Mon, Nov 17, 2014 at 04:15:46PM -0500, Tejun Heo wrote: > 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 <[email protected]> > Cc: Li Zefan <[email protected]> > Cc: Jens Axboe <[email protected]> > Cc: Vivek Goyal <[email protected]>
Looks good to me. Acked-by: Vivek Goyal <[email protected]> Vivek > --- > Hello, > > This one can be routed through either cgroup or block tree but I think > it'd be easier to route this through block as there will be more block > changes in the area. > > Thanks. > > block/bio.c | 11 +---------- > include/linux/cgroup.h | 25 +++++++++++++++++++++++++ > 2 files changed, 26 insertions(+), 10 deletions(-) > > --- a/block/bio.c > +++ b/block/bio.c > @@ -1997,7 +1997,6 @@ 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; > @@ -2006,17 +2005,9 @@ int bio_associate_current(struct bio *bi > 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; > } > > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -748,6 +748,31 @@ static inline struct cgroup_subsys_state > } > > /** > + * 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
