diff options
| -rw-r--r-- | block/bio.c | 62 | ||||
| -rw-r--r-- | include/linux/blk-cgroup.h | 52 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 2 | ||||
| -rw-r--r-- | kernel/cgroup/cgroup.c | 48 |
4 files changed, 81 insertions, 83 deletions
diff --git a/block/bio.c b/block/bio.c index 71cfe3720ea7..c39251e69447 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1978,18 +1978,30 @@ int bio_associate_blkg(struct bio *bio, struct blkcg_gq *blkg) return 0; } +/** + * __bio_associate_blkg_from_css - internal blkg association function + * + * This in the core association function that all association paths rely on. + * A blkg reference is taken which is released upon freeing of the bio. + */ static int __bio_associate_blkg_from_css(struct bio *bio, struct cgroup_subsys_state *css) { + struct request_queue *q = bio->bi_disk->queue; struct blkcg_gq *blkg; + int ret; rcu_read_lock(); - blkg = blkg_lookup_create(css_to_blkcg(css), bio->bi_disk->queue); + if (!css || !css->parent) + blkg = q->root_blkg; + else + blkg = blkg_lookup_create(css_to_blkcg(css), q); - rcu_read_unlock(); + ret = bio_associate_blkg(bio, blkg); - return bio_associate_blkg(bio, blkg); + rcu_read_unlock(); + return ret; } /** @@ -1998,13 +2010,14 @@ static int __bio_associate_blkg_from_css(struct bio *bio, * @css: target css * * Associate @bio with the blkg found by combining the css's blkg and the - * request_queue of the @bio. This takes a reference on the css that will - * be put upon freeing of @bio. + * request_queue of the @bio. This falls back to the queue's root_blkg if + * the association fails with the css. */ int bio_associate_blkg_from_css(struct bio *bio, struct cgroup_subsys_state *css) { - css_get(css); + if (unlikely(bio->bi_blkg)) + return -EBUSY; return __bio_associate_blkg_from_css(bio, css); } EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); @@ -2016,22 +2029,29 @@ EXPORT_SYMBOL_GPL(bio_associate_blkg_from_css); * @page: the page to lookup the blkcg from * * Associate @bio with the blkg from @page's owning memcg and the respective - * request_queue. This works like every other associate function wrt - * references. + * request_queue. If cgroup_e_css returns NULL, fall back to the queue's + * root_blkg. * * Note: this must be called after bio has an associated device. */ int bio_associate_blkg_from_page(struct bio *bio, struct page *page) { struct cgroup_subsys_state *css; + int ret; if (unlikely(bio->bi_blkg)) return -EBUSY; if (!page->mem_cgroup) return 0; - css = cgroup_get_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys); - return __bio_associate_blkg_from_css(bio, css); + rcu_read_lock(); + + css = cgroup_e_css(page->mem_cgroup->css.cgroup, &io_cgrp_subsys); + + ret = __bio_associate_blkg_from_css(bio, css); + + rcu_read_unlock(); + return ret; } #endif /* CONFIG_MEMCG */ @@ -2041,12 +2061,12 @@ int bio_associate_blkg_from_page(struct bio *bio, struct page *page) * @bio: target bio * * Associate @bio with the blkg found from the bio's css and the request_queue. - * If one is not found, bio_lookup_blkg creates the blkg. + * If one is not found, bio_lookup_blkg creates the blkg. This falls back to + * the queue's root_blkg if association fails. */ int bio_associate_create_blkg(struct request_queue *q, struct bio *bio) { - struct blkcg *blkcg; - struct blkcg_gq *blkg; + struct cgroup_subsys_state *css; int ret = 0; /* someone has already associated this bio with a blkg */ @@ -2055,15 +2075,9 @@ int bio_associate_create_blkg(struct request_queue *q, struct bio *bio) rcu_read_lock(); - blkcg = css_to_blkcg(blkcg_get_css()); + css = blkcg_css(); - if (!blkcg->css.parent) { - ret = bio_associate_blkg(bio, q->root_blkg); - } else { - blkg = blkg_lookup_create(blkcg, q); - - ret = bio_associate_blkg(bio, blkg); - } + ret = __bio_associate_blkg_from_css(bio, css); rcu_read_unlock(); return ret; @@ -2080,8 +2094,6 @@ void bio_disassociate_task(struct bio *bio) bio->bi_ioc = NULL; } if (bio->bi_blkg) { - /* a ref is always taken on css */ - css_put(&bio_blkcg(bio)->css); blkg_put(bio->bi_blkg); bio->bi_blkg = NULL; } @@ -2094,10 +2106,8 @@ void bio_disassociate_task(struct bio *bio) */ void bio_clone_blkg_association(struct bio *dst, struct bio *src) { - if (src->bi_blkg) { - css_get(&bio_blkcg(src)->css); + if (src->bi_blkg) bio_associate_blkg(dst, src->bi_blkg); - } } EXPORT_SYMBOL_GPL(bio_clone_blkg_association); #endif /* CONFIG_BLK_CGROUP */ diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h index c41cfcc2b4d8..2951ea3541b1 100644 --- a/include/linux/blk-cgroup.h +++ b/include/linux/blk-cgroup.h @@ -249,47 +249,6 @@ static inline struct cgroup_subsys_state *blkcg_css(void) return task_css(current, io_cgrp_id); } -/** - * blkcg_get_css - find and get a reference to the css - * - * Find the css associated with either the kthread or the current task. - * This takes a reference on the blkcg which will need to be managed by the - * caller. - */ -static inline struct cgroup_subsys_state *blkcg_get_css(void) -{ - struct cgroup_subsys_state *css; - - rcu_read_lock(); - - css = kthread_blkcg(); - if (css) { - css_get(css); - } else { - /* - * This is a bit complicated. It is possible task_css is seeing - * an old css pointer here. This is caused by the current - * thread migrating away from this cgroup and this cgroup dying. - * css_tryget() will fail when trying to take a ref on a cgroup - * that's ref count has hit 0. - * - * Therefore, if it does fail, this means current must have - * been swapped away already and this is waiting for it to - * propagate on the polling cpu. Hence the use of cpu_relax(). - */ - while (true) { - css = task_css(current, io_cgrp_id); - if (likely(css_tryget(css))) - break; - cpu_relax(); - } - } - - rcu_read_unlock(); - - return css; -} - static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css) { return css ? container_of(css, struct blkcg, css) : NULL; @@ -628,10 +587,8 @@ static inline struct request_list *blk_get_rl(struct request_queue *q, rcu_read_lock(); blkcg = bio_blkcg(bio); - if (blkcg) - css_get(&blkcg->css); - else - blkcg = css_to_blkcg(blkcg_get_css()); + if (!blkcg) + blkcg = css_to_blkcg(blkcg_css()); /* bypass blkg lookup and use @q->root_rl directly for root */ if (blkcg == &blkcg_root) @@ -646,7 +603,8 @@ static inline struct request_list *blk_get_rl(struct request_queue *q, if (unlikely(!blkg)) goto root_rl; - blkg_get(blkg); + if (!blkg_try_get(blkg)) + goto root_rl; rcu_read_unlock(); return &blkg->rl; root_rl: @@ -663,8 +621,6 @@ root_rl: */ static inline void blk_put_rl(struct request_list *rl) { - /* an additional ref is always taken for rl */ - css_put(&rl->blkg->blkcg->css); if (rl->blkg->blkcg != &blkcg_root) blkg_put(rl->blkg); } diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 32c553556bbd..b8bcbdeb2eac 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -93,6 +93,8 @@ extern struct css_set init_css_set; bool css_has_online_children(struct cgroup_subsys_state *css); struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss); +struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgroup, + struct cgroup_subsys *ss); struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, struct cgroup_subsys *ss); struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index aae10baf1902..48fb22e49467 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -492,7 +492,7 @@ static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp, } /** - * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem + * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss * @cgrp: the cgroup of interest * @ss: the subsystem of interest (%NULL returns @cgrp->self) * @@ -501,8 +501,8 @@ static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp, * enabled. If @ss is associated with the hierarchy @cgrp is on, this * function is guaranteed to return non-NULL css. */ -static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, - struct cgroup_subsys *ss) +static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp, + struct cgroup_subsys *ss) { lockdep_assert_held(&cgroup_mutex); @@ -523,6 +523,35 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, } /** + * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem + * @cgrp: the cgroup of interest + * @ss: the subsystem of interest + * + * Find and get the effective css of @cgrp for @ss. The effective css is + * defined as the matching css of the nearest ancestor including self which + * has @ss enabled. If @ss is not mounted on the hierarchy @cgrp is on, + * the root css is returned, so this function always returns a valid css. + * + * The returned css is not guaranteed to be online, and therefore it is the + * callers responsiblity to tryget a reference for it. + */ +struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, + struct cgroup_subsys *ss) +{ + struct cgroup_subsys_state *css; + + do { + css = cgroup_css(cgrp, ss); + + if (css) + return css; + cgrp = cgroup_parent(cgrp); + } while (cgrp); + + return init_css_set.subsys[ss->id]; +} + +/** * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem * @cgrp: the cgroup of interest * @ss: the subsystem of interest @@ -604,10 +633,11 @@ EXPORT_SYMBOL_GPL(of_css); * * Should be called under cgroup_[tree_]mutex. */ -#define for_each_e_css(css, ssid, cgrp) \ - for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ - if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \ - ; \ +#define for_each_e_css(css, ssid, cgrp) \ + for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \ + if (!((css) = cgroup_e_css_by_mask(cgrp, \ + cgroup_subsys[(ssid)]))) \ + ; \ else /** @@ -1006,7 +1036,7 @@ static struct css_set *find_existing_css_set(struct css_set *old_cset, * @ss is in this hierarchy, so we want the * effective css from @cgrp. */ - template[i] = cgroup_e_css(cgrp, ss); + template[i] = cgroup_e_css_by_mask(cgrp, ss); } else { /* * @ss is not in this hierarchy, so we don't want @@ -3019,7 +3049,7 @@ static int cgroup_apply_control(struct cgroup *cgrp) return ret; /* - * At this point, cgroup_e_css() results reflect the new csses + * At this point, cgroup_e_css_by_mask() results reflect the new csses * making the following cgroup_update_dfl_csses() properly update * css associations of all tasks in the subtree. */ |