#include <linux/blkdev.h>
#include <linux/atomic.h>
#include <linux/kthread.h>
+#include <linux/fs.h>
/* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
#define BLKG_STAT_CPU_BATCH (INT_MAX / 2)
/* all non-root blkcg_gq's are guaranteed to have access to parent */
struct blkcg_gq *parent;
- /* request allocation list for this blkcg-q pair */
- struct request_list rl;
-
/* reference count */
atomic_t refcnt;
struct blkcg_gq *blkg_lookup_slowpath(struct blkcg *blkcg,
struct request_queue *q, bool update_hint);
+struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
+ struct request_queue *q);
struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
struct request_queue *q);
int blkcg_init_queue(struct request_queue *q);
char *input, struct blkg_conf_ctx *ctx);
void blkg_conf_finish(struct blkg_conf_ctx *ctx);
+/**
+ * blkcg_css - find the current css
+ *
+ * Find the css associated with either the kthread or the current task.
+ * This may return a dying css, so it is up to the caller to use tryget logic
+ * to confirm it is alive and well.
+ */
+static inline struct cgroup_subsys_state *blkcg_css(void)
+{
+ struct cgroup_subsys_state *css;
+
+ css = kthread_blkcg();
+ if (css)
+ return css;
+ 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;
}
-static inline struct blkcg *bio_blkcg(struct bio *bio)
+/**
+ * __bio_blkcg - internal, inconsistent version to get blkcg
+ *
+ * DO NOT USE.
+ * This function is inconsistent and consequently is dangerous to use. The
+ * first part of the function returns a blkcg where a reference is owned by the
+ * bio. This means it does not need to be rcu protected as it cannot go away
+ * with the bio owning a reference to it. However, the latter potentially gets
+ * it from task_css(). This can race against task migration and the cgroup
+ * dying. It is also semantically different as it must be called rcu protected
+ * and is susceptible to failure when trying to get a reference to it.
+ * Therefore, it is not ok to assume that *_get() will always succeed on the
+ * blkcg returned here.
+ */
+static inline struct blkcg *__bio_blkcg(struct bio *bio)
{
- struct cgroup_subsys_state *css;
+ if (bio && bio->bi_css)
+ return css_to_blkcg(bio->bi_css);
+ return css_to_blkcg(blkcg_css());
+}
+/**
+ * bio_blkcg - grab the blkcg associated with a bio
+ * @bio: target bio
+ *
+ * This returns the blkcg associated with a bio, %NULL if not associated.
+ * Callers are expected to either handle %NULL or know association has been
+ * done prior to calling this.
+ */
+static inline struct blkcg *bio_blkcg(struct bio *bio)
+{
if (bio && bio->bi_css)
return css_to_blkcg(bio->bi_css);
- css = kthread_blkcg();
- if (css)
- return css_to_blkcg(css);
- return css_to_blkcg(task_css(current, io_cgrp_id));
+ return NULL;
}
static inline bool blk_cgroup_congested(void)
* @q: request_queue of interest
*
* Lookup blkg for the @blkcg - @q pair. This function should be called
- * under RCU read lock and is guaranteed to return %NULL if @q is bypassing
- * - see blk_queue_bypass_start() for details.
+ * under RCU read loc.
*/
static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg,
struct request_queue *q)
{
WARN_ON_ONCE(!rcu_read_lock_held());
-
- if (unlikely(blk_queue_bypass(q)))
- return NULL;
return __blkg_lookup(blkcg, q, false);
}
return NULL;
}
+/**
+ * blkg_try_get_closest - try and get a blkg ref on the closet blkg
+ * @blkg: blkg to get
+ *
+ * This walks up the blkg tree to find the closest non-dying blkg and returns
+ * the blkg that it did association with as it may not be the passed in blkg.
+ */
+static inline struct blkcg_gq *blkg_try_get_closest(struct blkcg_gq *blkg)
+{
+ while (!atomic_inc_not_zero(&blkg->refcnt))
+ blkg = blkg->parent;
+
+ return blkg;
+}
void __blkg_release_rcu(struct rcu_head *rcu);
if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css), \
(p_blkg)->q, false)))
-/**
- * blk_get_rl - get request_list to use
- * @q: request_queue of interest
- * @bio: bio which will be attached to the allocated request (may be %NULL)
- *
- * The caller wants to allocate a request from @q to use for @bio. Find
- * the request_list to use and obtain a reference on it. Should be called
- * under queue_lock. This function is guaranteed to return non-%NULL
- * request_list.
- */
-static inline struct request_list *blk_get_rl(struct request_queue *q,
- struct bio *bio)
-{
- struct blkcg *blkcg;
- struct blkcg_gq *blkg;
-
- rcu_read_lock();
-
- blkcg = bio_blkcg(bio);
-
- /* bypass blkg lookup and use @q->root_rl directly for root */
- if (blkcg == &blkcg_root)
- goto root_rl;
-
- /*
- * Try to use blkg->rl. blkg lookup may fail under memory pressure
- * or if either the blkcg or queue is going away. Fall back to
- * root_rl in such cases.
- */
- blkg = blkg_lookup(blkcg, q);
- if (unlikely(!blkg))
- goto root_rl;
-
- blkg_get(blkg);
- rcu_read_unlock();
- return &blkg->rl;
-root_rl:
- rcu_read_unlock();
- return &q->root_rl;
-}
-
-/**
- * blk_put_rl - put request_list
- * @rl: request_list to put
- *
- * Put the reference acquired by blk_get_rl(). Should be called under
- * queue_lock.
- */
-static inline void blk_put_rl(struct request_list *rl)
-{
- if (rl->blkg->blkcg != &blkcg_root)
- blkg_put(rl->blkg);
-}
-
-/**
- * blk_rq_set_rl - associate a request with a request_list
- * @rq: request of interest
- * @rl: target request_list
- *
- * Associate @rq with @rl so that accounting and freeing can know the
- * request_list @rq came from.
- */
-static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
-{
- rq->rl = rl;
-}
-
-/**
- * blk_rq_rl - return the request_list a request came from
- * @rq: request of interest
- *
- * Return the request_list @rq is allocated from.
- */
-static inline struct request_list *blk_rq_rl(struct request *rq)
-{
- return rq->rl;
-}
-
-struct request_list *__blk_queue_next_rl(struct request_list *rl,
- struct request_queue *q);
-/**
- * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
- *
- * Should be used under queue_lock.
- */
-#define blk_queue_for_each_rl(rl, q) \
- for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
-
static inline int blkg_stat_init(struct blkg_stat *stat, gfp_t gfp)
{
int ret;
static inline bool blkcg_bio_issue_check(struct request_queue *q,
struct bio *bio)
{
- struct blkcg *blkcg;
struct blkcg_gq *blkg;
bool throtl = false;
- rcu_read_lock();
- blkcg = bio_blkcg(bio);
-
- /* associate blkcg if bio hasn't attached one */
- bio_associate_blkcg(bio, &blkcg->css);
-
- blkg = blkg_lookup(blkcg, q);
- if (unlikely(!blkg)) {
- spin_lock_irq(q->queue_lock);
- blkg = blkg_lookup_create(blkcg, q);
- if (IS_ERR(blkg))
- blkg = NULL;
- spin_unlock_irq(q->queue_lock);
+ if (!bio->bi_blkg) {
+ char b[BDEVNAME_SIZE];
+
+ WARN_ONCE(1,
+ "no blkg associated for bio on block-device: %s\n",
+ bio_devname(bio, b));
+ bio_associate_blkg(bio);
}
+ blkg = bio->bi_blkg;
+
throtl = blk_throtl_bio(q, blkg, bio);
if (!throtl) {
- blkg = blkg ?: q->root_blkg;
/*
* If the bio is flagged with BIO_QUEUE_ENTERED it means this
* is a split bio and we would have already accounted for the
blkg_rwstat_add(&blkg->stat_ios, bio->bi_opf, 1);
}
- rcu_read_unlock();
return !throtl;
}
static inline void blkcg_deactivate_policy(struct request_queue *q,
const struct blkcg_policy *pol) { }
+static inline struct blkcg *__bio_blkcg(struct bio *bio) { return NULL; }
static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
static inline void blkg_get(struct blkcg_gq *blkg) { }
static inline void blkg_put(struct blkcg_gq *blkg) { }
-static inline struct request_list *blk_get_rl(struct request_queue *q,
- struct bio *bio) { return &q->root_rl; }
-static inline void blk_put_rl(struct request_list *rl) { }
-static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
-static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
-
static inline bool blkcg_bio_issue_check(struct request_queue *q,
struct bio *bio) { return true; }
git.samba.org / sfrench / cifs-2.6.git / blobdiff