#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 */
struct percpu_ref refcnt;
}
/**
- * __bio_blkcg - internal version of bio_blkcg for bfq and cfq
+ * __bio_blkcg - internal, inconsistent version to get blkcg
*
* DO NOT USE.
- * There is a flaw using this version of the function. In particular, this was
- * used in a broken paradigm where association was called on the given css. It
- * is possible though that the returned css from task_css() is in the process
- * of dying due to migration of the current task. So it is improper to assume
- * *_get() is going to succeed. Both BFQ and CFQ rely on this logic and will
- * take additional work to handle more gracefully.
+ * 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)
{
* 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
+ * 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)
* @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);
}
}
/**
- * blkg_tryget - try and get a blkg reference
+ * blkg_try_get - try and get a blkg reference
* @blkg: blkg to get
*
* This is for use when doing an RCU lookup of the blkg. We may be in the midst
* of freeing this blkg, so we can only use it if the refcnt is not zero.
*/
-static inline bool blkg_tryget(struct blkcg_gq *blkg)
+static inline struct blkcg_gq *blkg_try_get(struct blkcg_gq *blkg)
{
- return percpu_ref_tryget(&blkg->refcnt);
+ if (percpu_ref_tryget(&blkg->refcnt))
+ return blkg;
+ return NULL;
}
/**
- * blkg_tryget_closest - try and get a blkg ref on the closet blkg
+ * 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_tryget_closest(struct blkcg_gq *blkg)
+static inline struct blkcg_gq *blkg_try_get_closest(struct blkcg_gq *blkg)
{
while (!percpu_ref_tryget(&blkg->refcnt))
blkg = blkg->parent;
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();
-
- if (bio && bio->bi_blkg) {
- blkcg = bio->bi_blkg->blkcg;
- if (blkcg == &blkcg_root)
- goto rl_use_root;
-
- blkg_get(bio->bi_blkg);
- rcu_read_unlock();
- return &bio->bi_blkg->rl;
- }
-
- blkcg = css_to_blkcg(blkcg_css());
- if (blkcg == &blkcg_root)
- goto rl_use_root;
-
- blkg = blkg_lookup(blkcg, q);
- if (unlikely(!blkg))
- blkg = __blkg_lookup_create(blkcg, q);
-
- if (blkg->blkcg == &blkcg_root || !blkg_tryget(blkg))
- goto rl_use_root;
-
- rcu_read_unlock();
- return &blkg->rl;
-
- /*
- * Each blkg has its own request_list, however, the root blkcg
- * uses the request_queue's root_rl. This is to avoid most
- * overhead for the root blkcg.
- */
-rl_use_root:
- 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;
struct blkcg_gq *blkg;
bool throtl = false;
- rcu_read_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);
+ }
- bio_associate_create_blkg(q, bio);
blkg = bio->bi_blkg;
throtl = blk_throtl_bio(q, blkg, bio);
blkcg_bio_issue_init(bio);
- rcu_read_unlock();
return !throtl;
}
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 void blkcg_bio_issue_init(struct bio *bio) { }
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