Merge branch 'for-3.9/core' of git://git.kernel.dk/linux-block

Pull block IO core bits from Jens Axboe:
 "Below are the core block IO bits for 3.9.  It was delayed a few days
  since my workstation kept crashing every 2-8h after pulling it into
  current -git, but turns out it is a bug in the new pstate code (divide
  by zero, will report separately).  In any case, it contains:

   - The big cfq/blkcg update from Tejun and and Vivek.

   - Additional block and writeback tracepoints from Tejun.

   - Improvement of the should sort (based on queues) logic in the plug
     flushing.

   - _io() variants of the wait_for_completion() interface, using
     io_schedule() instead of schedule() to contribute to io wait
     properly.

   - Various little fixes.

  You'll get two trivial merge conflicts, which should be easy enough to
  fix up"

Fix up the trivial conflicts due to hlist traversal cleanups (commit
b67bfe0d42ca: "hlist: drop the node parameter from iterators").

* 'for-3.9/core' of git://git.kernel.dk/linux-block: (39 commits)
  block: remove redundant check to bd_openers()
  block: use i_size_write() in bd_set_size()
  cfq: fix lock imbalance with failed allocations
  drivers/block/swim3.c: fix null pointer dereference
  block: don't select PERCPU_RWSEM
  block: account iowait time when waiting for completion of IO request
  sched: add wait_for_completion_io[_timeout]
  writeback: add more tracepoints
  block: add block_{touch|dirty}_buffer tracepoint
  buffer: make touch_buffer() an exported function
  block: add @req to bio_{front|back}_merge tracepoints
  block: add missing block_bio_complete() tracepoint
  block: Remove should_sort judgement when flush blk_plug
  block,elevator: use new hashtable implementation
  cfq-iosched: add hierarchical cfq_group statistics
  cfq-iosched: collect stats from dead cfqgs
  cfq-iosched: separate out cfqg_stats_reset() from cfq_pd_reset_stats()
  blkcg: make blkcg_print_blkgs() grab q locks instead of blkcg lock
  block: RCU free request_queue
  blkcg: implement blkg_[rw]stat_recursive_sum() and blkg_[rw]stat_merge()
  ...

1 files changed, 236 insertions, 41 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8bdebb6781e1..b2b9837f9dd3 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -26,11 +26,32 @@
 
 static DEFINE_MUTEX(blkcg_pol_mutex);
 
-struct blkcg blkcg_root = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT };
+struct blkcg blkcg_root = { .cfq_weight = 2 * CFQ_WEIGHT_DEFAULT,
+                            .cfq_leaf_weight = 2 * CFQ_WEIGHT_DEFAULT, };
 EXPORT_SYMBOL_GPL(blkcg_root);
 
 static struct blkcg_policy *blkcg_policy[BLKCG_MAX_POLS];
 
+static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
+                                      struct request_queue *q, bool update_hint);
+
+/**
+ * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
+ * @d_blkg: loop cursor pointing to the current descendant
+ * @pos_cgrp: used for iteration
+ * @p_blkg: target blkg to walk descendants of
+ *
+ * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
+ * read locked.  If called under either blkcg or queue lock, the iteration
+ * is guaranteed to include all and only online blkgs.  The caller may
+ * update @pos_cgrp by calling cgroup_rightmost_descendant() to skip
+ * subtree.
+ */
+#define blkg_for_each_descendant_pre(d_blkg, pos_cgrp, p_blkg)          \
+        cgroup_for_each_descendant_pre((pos_cgrp), (p_blkg)->blkcg->css.cgroup) \
+                if (((d_blkg) = __blkg_lookup(cgroup_to_blkcg(pos_cgrp), \
+                                              (p_blkg)->q, false)))
+
 static bool blkcg_policy_enabled(struct request_queue *q,
                                  const struct blkcg_policy *pol)
 {
@@ -112,9 +133,10 @@ static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 
                 blkg->pd[i] = pd;
                 pd->blkg = blkg;
+                pd->plid = i;
 
                 /* invoke per-policy init */
-                if (blkcg_policy_enabled(blkg->q, pol))
+                if (pol->pd_init_fn)
                         pol->pd_init_fn(blkg);
         }
 
@@ -125,8 +147,19 @@ err_free:
         return NULL;
 }
 
+/**
+ * __blkg_lookup - internal version of blkg_lookup()
+ * @blkcg: blkcg of interest
+ * @q: request_queue of interest
+ * @update_hint: whether to update lookup hint with the result or not
+ *
+ * This is internal version and shouldn't be used by policy
+ * implementations.  Looks up blkgs for the @blkcg - @q pair regardless of
+ * @q's bypass state.  If @update_hint is %true, the caller should be
+ * holding @q->queue_lock and lookup hint is updated on success.
+ */
 static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
-                                      struct request_queue *q)
+                                      struct request_queue *q, bool update_hint)
 {
         struct blkcg_gq *blkg;
 
@@ -135,14 +168,19 @@ static struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg,
                 return blkg;
 
         /*
-         * Hint didn't match.  Look up from the radix tree.  Note that we
-         * may not be holding queue_lock and thus are not sure whether
-         * @blkg from blkg_tree has already been removed or not, so we
-         * can't update hint to the lookup result.  Leave it to the caller.
+         * Hint didn't match.  Look up from the radix tree.  Note that the
+         * hint can only be updated under queue_lock as otherwise @blkg
+         * could have already been removed from blkg_tree.  The caller is
+         * responsible for grabbing queue_lock if @update_hint.
          */
         blkg = radix_tree_lookup(&blkcg->blkg_tree, q->id);
-        if (blkg && blkg->q == q)
+        if (blkg && blkg->q == q) {
+                if (update_hint) {
+                        lockdep_assert_held(q->queue_lock);
+                        rcu_assign_pointer(blkcg->blkg_hint, blkg);
+                }
                 return blkg;
+        }
 
         return NULL;
 }
@@ -162,7 +200,7 @@ struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q)
 
         if (unlikely(blk_queue_bypass(q)))
                 return NULL;
-        return __blkg_lookup(blkcg, q);
+        return __blkg_lookup(blkcg, q, false);
 }
 EXPORT_SYMBOL_GPL(blkg_lookup);
 
@@ -170,75 +208,129 @@ EXPORT_SYMBOL_GPL(blkg_lookup);
  * If @new_blkg is %NULL, this function tries to allocate a new one as
  * necessary using %GFP_ATOMIC.  @new_blkg is always consumed on return.
  */
-static struct blkcg_gq *__blkg_lookup_create(struct blkcg *blkcg,
-                                             struct request_queue *q,
-                                             struct blkcg_gq *new_blkg)
+static struct blkcg_gq *blkg_create(struct blkcg *blkcg,
+                                    struct request_queue *q,
+                                    struct blkcg_gq *new_blkg)
 {
         struct blkcg_gq *blkg;
-        int ret;
+        int i, ret;
 
         WARN_ON_ONCE(!rcu_read_lock_held());
         lockdep_assert_held(q->queue_lock);
 
-        /* lookup and update hint on success, see __blkg_lookup() for details */
-        blkg = __blkg_lookup(blkcg, q);
-        if (blkg) {
-                rcu_assign_pointer(blkcg->blkg_hint, blkg);
-                goto out_free;
-        }
-
         /* blkg holds a reference to blkcg */
         if (!css_tryget(&blkcg->css)) {
-                blkg = ERR_PTR(-EINVAL);
-                goto out_free;
+                ret = -EINVAL;
+                goto err_free_blkg;
         }
 
         /* allocate */
         if (!new_blkg) {
                 new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
                 if (unlikely(!new_blkg)) {
-                        blkg = ERR_PTR(-ENOMEM);
-                        goto out_put;
+                        ret = -ENOMEM;
+                        goto err_put_css;
                 }
         }
         blkg = new_blkg;
 
-        /* insert */
+        /* link parent and insert */
+        if (blkcg_parent(blkcg)) {
+                blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
+                if (WARN_ON_ONCE(!blkg->parent)) {
+                        blkg = ERR_PTR(-EINVAL);
+                        goto err_put_css;
+                }
+                blkg_get(blkg->parent);
+        }
+
         spin_lock(&blkcg->lock);
         ret = radix_tree_insert(&blkcg->blkg_tree, q->id, blkg);
         if (likely(!ret)) {
                 hlist_add_head_rcu(&blkg->blkcg_node, &blkcg->blkg_list);
                 list_add(&blkg->q_node, &q->blkg_list);
+
+                for (i = 0; i < BLKCG_MAX_POLS; i++) {
+                        struct blkcg_policy *pol = blkcg_policy[i];
+
+                        if (blkg->pd[i] && pol->pd_online_fn)
+                                pol->pd_online_fn(blkg);
+                }
         }
+        blkg->online = true;
         spin_unlock(&blkcg->lock);
 
         if (!ret)
                 return blkg;
 
-        blkg = ERR_PTR(ret);
-out_put:
+        /* @blkg failed fully initialized, use the usual release path */
+        blkg_put(blkg);
+        return ERR_PTR(ret);
+
+err_put_css:
         css_put(&blkcg->css);
-out_free:
+err_free_blkg:
         blkg_free(new_blkg);
-        return blkg;
+        return ERR_PTR(ret);
 }
 
+/**
+ * blkg_lookup_create - lookup blkg, try to create one if not there
+ * @blkcg: blkcg of interest
+ * @q: request_queue of interest
+ *
+ * Lookup blkg for the @blkcg - @q pair.  If it doesn't exist, try to
+ * create one.  blkg creation is performed recursively from blkcg_root such
+ * that all non-root blkg's have access to the parent blkg.  This function
+ * should be called under RCU read lock and @q->queue_lock.
+ *
+ * Returns pointer to the looked up or created blkg on success, ERR_PTR()
+ * value on error.  If @q is dead, returns ERR_PTR(-EINVAL).  If @q is not
+ * dead and bypassing, returns ERR_PTR(-EBUSY).
+ */
 struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
                                     struct request_queue *q)
 {
+        struct blkcg_gq *blkg;
+
+        WARN_ON_ONCE(!rcu_read_lock_held());
+        lockdep_assert_held(q->queue_lock);
+
         /*
          * This could be the first entry point of blkcg implementation and
          * we shouldn't allow anything to go through for a bypassing queue.
          */
         if (unlikely(blk_queue_bypass(q)))
                 return ERR_PTR(blk_queue_dying(q) ? -EINVAL : -EBUSY);
-        return __blkg_lookup_create(blkcg, q, NULL);
+
+        blkg = __blkg_lookup(blkcg, q, true);
+        if (blkg)
+                return blkg;
+
+        /*
+         * Create blkgs walking down from blkcg_root to @blkcg, so that all
+         * non-root blkgs have access to their parents.
+         */
+        while (true) {
+                struct blkcg *pos = blkcg;
+                struct blkcg *parent = blkcg_parent(blkcg);
+
+                while (parent && !__blkg_lookup(parent, q, false)) {
+                        pos = parent;
+                        parent = blkcg_parent(parent);
+                }
+
+                blkg = blkg_create(pos, q, NULL);
+                if (pos == blkcg || IS_ERR(blkg))
+                        return blkg;
+        }
 }
 EXPORT_SYMBOL_GPL(blkg_lookup_create);
 
 static void blkg_destroy(struct blkcg_gq *blkg)
 {
         struct blkcg *blkcg = blkg->blkcg;
+        int i;
 
         lockdep_assert_held(blkg->q->queue_lock);
         lockdep_assert_held(&blkcg->lock);
@@ -247,6 +339,14 @@ static void blkg_destroy(struct blkcg_gq *blkg)
         WARN_ON_ONCE(list_empty(&blkg->q_node));
         WARN_ON_ONCE(hlist_unhashed(&blkg->blkcg_node));
 
+        for (i = 0; i < BLKCG_MAX_POLS; i++) {
+                struct blkcg_policy *pol = blkcg_policy[i];
+
+                if (blkg->pd[i] && pol->pd_offline_fn)
+                        pol->pd_offline_fn(blkg);
+        }
+        blkg->online = false;
+
         radix_tree_delete(&blkcg->blkg_tree, blkg->q->id);
         list_del_init(&blkg->q_node);
         hlist_del_init_rcu(&blkg->blkcg_node);
@@ -301,8 +401,10 @@ static void blkg_rcu_free(struct rcu_head *rcu_head)
 
 void __blkg_release(struct blkcg_gq *blkg)
 {
-        /* release the extra blkcg reference this blkg has been holding */
+        /* release the blkcg and parent blkg refs this blkg has been holding */
         css_put(&blkg->blkcg->css);
+        if (blkg->parent)
+                blkg_put(blkg->parent);
 
         /*
          * A group is freed in rcu manner. But having an rcu lock does not
@@ -401,8 +503,9 @@ static const char *blkg_dev_name(struct blkcg_gq *blkg)
  *
  * This function invokes @prfill on each blkg of @blkcg if pd for the
  * policy specified by @pol exists.  @prfill is invoked with @sf, the
- * policy data and @data.  If @show_total is %true, the sum of the return
- * values from @prfill is printed with "Total" label at the end.
+ * policy data and @data and the matching queue lock held.  If @show_total
+ * is %true, the sum of the return values from @prfill is printed with
+ * "Total" label at the end.
  *
  * This is to be used to construct print functions for
  * cftype->read_seq_string method.
@@ -416,11 +519,14 @@ void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
         struct blkcg_gq *blkg;
         u64 total = 0;
 
-        spin_lock_irq(&blkcg->lock);
-        hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node)
+        rcu_read_lock();
+        hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
+                spin_lock_irq(blkg->q->queue_lock);
                 if (blkcg_policy_enabled(blkg->q, pol))
                         total += prfill(sf, blkg->pd[pol->plid], data);
-        spin_unlock_irq(&blkcg->lock);
+                spin_unlock_irq(blkg->q->queue_lock);
+        }
+        rcu_read_unlock();
 
         if (show_total)
                 seq_printf(sf, "Total %llu\n", (unsigned long long)total);
@@ -479,6 +585,7 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
         seq_printf(sf, "%s Total %llu\n", dname, (unsigned long long)v);
         return v;
 }
+EXPORT_SYMBOL_GPL(__blkg_prfill_rwstat);
 
 /**
  * blkg_prfill_stat - prfill callback for blkg_stat
@@ -512,6 +619,82 @@ u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 EXPORT_SYMBOL_GPL(blkg_prfill_rwstat);
 
 /**
+ * blkg_stat_recursive_sum - collect hierarchical blkg_stat
+ * @pd: policy private data of interest
+ * @off: offset to the blkg_stat in @pd
+ *
+ * Collect the blkg_stat specified by @off from @pd and all its online
+ * descendants and return the sum.  The caller must be holding the queue
+ * lock for online tests.
+ */
+u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off)
+{
+        struct blkcg_policy *pol = blkcg_policy[pd->plid];
+        struct blkcg_gq *pos_blkg;
+        struct cgroup *pos_cgrp;
+        u64 sum;
+
+        lockdep_assert_held(pd->blkg->q->queue_lock);
+
+        sum = blkg_stat_read((void *)pd + off);
+
+        rcu_read_lock();
+        blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
+                struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
+                struct blkg_stat *stat = (void *)pos_pd + off;
+
+                if (pos_blkg->online)
+                        sum += blkg_stat_read(stat);
+        }
+        rcu_read_unlock();
+
+        return sum;
+}
+EXPORT_SYMBOL_GPL(blkg_stat_recursive_sum);
+
+/**
+ * blkg_rwstat_recursive_sum - collect hierarchical blkg_rwstat
+ * @pd: policy private data of interest
+ * @off: offset to the blkg_stat in @pd
+ *
+ * Collect the blkg_rwstat specified by @off from @pd and all its online
+ * descendants and return the sum.  The caller must be holding the queue
+ * lock for online tests.
+ */
+struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
+                                             int off)
+{
+        struct blkcg_policy *pol = blkcg_policy[pd->plid];
+        struct blkcg_gq *pos_blkg;
+        struct cgroup *pos_cgrp;
+        struct blkg_rwstat sum;
+        int i;
+
+        lockdep_assert_held(pd->blkg->q->queue_lock);
+
+        sum = blkg_rwstat_read((void *)pd + off);
+
+        rcu_read_lock();
+        blkg_for_each_descendant_pre(pos_blkg, pos_cgrp, pd_to_blkg(pd)) {
+                struct blkg_policy_data *pos_pd = blkg_to_pd(pos_blkg, pol);
+                struct blkg_rwstat *rwstat = (void *)pos_pd + off;
+                struct blkg_rwstat tmp;
+
+                if (!pos_blkg->online)
+                        continue;
+
+                tmp = blkg_rwstat_read(rwstat);
+
+                for (i = 0; i < BLKG_RWSTAT_NR; i++)
+                        sum.cnt[i] += tmp.cnt[i];
+        }
+        rcu_read_unlock();
+
+        return sum;
+}
+EXPORT_SYMBOL_GPL(blkg_rwstat_recursive_sum);
+
+/**
  * blkg_conf_prep - parse and prepare for per-blkg config update
  * @blkcg: target block cgroup
  * @pol: target policy
@@ -656,6 +839,7 @@ static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
                 return ERR_PTR(-ENOMEM);
 
         blkcg->cfq_weight = CFQ_WEIGHT_DEFAULT;
+        blkcg->cfq_leaf_weight = CFQ_WEIGHT_DEFAULT;
         blkcg->id = atomic64_inc_return(&id_seq); /* root is 0, start from 1 */
 done:
         spin_lock_init(&blkcg->lock);
@@ -775,7 +959,7 @@ int blkcg_activate_policy(struct request_queue *q,
                           const struct blkcg_policy *pol)
 {
         LIST_HEAD(pds);
-        struct blkcg_gq *blkg;
+        struct blkcg_gq *blkg, *new_blkg;
         struct blkg_policy_data *pd, *n;
         int cnt = 0, ret;
         bool preloaded;
@@ -784,19 +968,27 @@ int blkcg_activate_policy(struct request_queue *q,
                 return 0;
 
         /* preallocations for root blkg */
-        blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
-        if (!blkg)
+        new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
+        if (!new_blkg)
                 return -ENOMEM;
 
         preloaded = !radix_tree_preload(GFP_KERNEL);
 
         blk_queue_bypass_start(q);
 
-        /* make sure the root blkg exists and count the existing blkgs */
+        /*
+         * Make sure the root blkg exists and count the existing blkgs.  As
+         * @q is bypassing at this point, blkg_lookup_create() can't be
+         * used.  Open code it.
+         */
         spin_lock_irq(q->queue_lock);
 
         rcu_read_lock();
-        blkg = __blkg_lookup_create(&blkcg_root, q, blkg);
+        blkg = __blkg_lookup(&blkcg_root, q, false);
+        if (blkg)
+                blkg_free(new_blkg);
+        else
+                blkg = blkg_create(&blkcg_root, q, new_blkg);
         rcu_read_unlock();
 
         if (preloaded)
@@ -844,6 +1036,7 @@ int blkcg_activate_policy(struct request_queue *q,
 
                 blkg->pd[pol->plid] = pd;
                 pd->blkg = blkg;
+                pd->plid = pol->plid;
                 pol->pd_init_fn(blkg);
 
                 spin_unlock(&blkg->blkcg->lock);
@@ -890,6 +1083,8 @@ void blkcg_deactivate_policy(struct request_queue *q,
                 /* grab blkcg lock too while removing @pd from @blkg */
                 spin_lock(&blkg->blkcg->lock);
 
+                if (pol->pd_offline_fn)
+                        pol->pd_offline_fn(blkg);
                 if (pol->pd_exit_fn)
                         pol->pd_exit_fn(blkg);