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Commit 2a4fd070ee8561d918a3776388331bb7e92ea59e

Authored by Tejun Heo 2013-05-15 04:52:31 +0800

Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch

blkcg: move bulk of blkcg_gq release operations to the RCU callback

Currently, when the last reference of a blkcg_gq is put, all then
release operations sans the actual freeing happen directly in
blkg_put().  As blkg_put() may be called under queue_lock, all
pd_exit_fn()s may be too.  This makes it impossible for pd_exit_fn()s
to use del_timer_sync() on timers which grab the queue_lock which is
an irq-safe lock due to the deadlock possibility described in the
comment on top of del_timer_sync().

This can be easily avoided by perfoming the release operations in the
RCU callback instead of directly from blkg_put().  This patch moves
the blkcg_gq release operations to the RCU callback.

As this leaves __blkg_release() with only call_rcu() invocation,
blkg_rcu_free() is renamed to __blkg_release_rcu(), exported and
call_rcu() invocation is now done directly from blkg_put() instead of
going through __blkg_release() which is removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

Showing 2 changed files with 18 additions and 20 deletions Inline Diff

block/blk-cgroup.c
block/blk-cgroup.h

block/blk-cgroup.c

Diff comments View file @ 2a4fd07

 /*
  * Common Block IO controller cgroup interface
  *
  * Based on ideas and code from CFQ, CFS and BFQ:
  * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
  *
  * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
  *		      Paolo Valente <paolo.valente@unimore.it>
  *
  * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
  * 	              Nauman Rafique <nauman@google.com>
  */
 #include <linux/ioprio.h>
 #include <linux/kdev_t.h>
 #include <linux/module.h>
 #include <linux/err.h>
 #include <linux/blkdev.h>
 #include <linux/slab.h>
 #include <linux/genhd.h>
 #include <linux/delay.h>
 #include <linux/atomic.h>
 #include "blk-cgroup.h"
 #include "blk.h"
 #define MAX_KEY_LEN 100
 static DEFINE_MUTEX(blkcg_pol_mutex);
 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 bool blkcg_policy_enabled(struct request_queue *q,
 				 const struct blkcg_policy *pol)
 {
 	return pol && test_bit(pol->plid, q->blkcg_pols);
 }
 /**
  * blkg_free - free a blkg
  * @blkg: blkg to free
  *
  * Free @blkg which may be partially allocated.
  */
 static void blkg_free(struct blkcg_gq *blkg)
 {
 	int i;
 	if (!blkg)
 		return;
 	for (i = 0; i < BLKCG_MAX_POLS; i++)
 		kfree(blkg->pd[i]);
 	blk_exit_rl(&blkg->rl);
 	kfree(blkg);
 }
 /**
  * blkg_alloc - allocate a blkg
  * @blkcg: block cgroup the new blkg is associated with
  * @q: request_queue the new blkg is associated with
  * @gfp_mask: allocation mask to use
  *
  * Allocate a new blkg assocating @blkcg and @q.
  */
 static struct blkcg_gq *blkg_alloc(struct blkcg *blkcg, struct request_queue *q,
 				   gfp_t gfp_mask)
 {
 	struct blkcg_gq *blkg;
 	int i;
 	/* alloc and init base part */
 	blkg = kzalloc_node(sizeof(*blkg), gfp_mask, q->node);
 	if (!blkg)
 		return NULL;
 	blkg->q = q;
 	INIT_LIST_HEAD(&blkg->q_node);
 	blkg->blkcg = blkcg;
 	blkg->refcnt = 1;
 	/* root blkg uses @q->root_rl, init rl only for !root blkgs */
 	if (blkcg != &blkcg_root) {
 		if (blk_init_rl(&blkg->rl, q, gfp_mask))
 			goto err_free;
 		blkg->rl.blkg = blkg;
 	}
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
 		struct blkg_policy_data *pd;
 		if (!blkcg_policy_enabled(q, pol))
 			continue;
 		/* alloc per-policy data and attach it to blkg */
 		pd = kzalloc_node(pol->pd_size, gfp_mask, q->node);
 		if (!pd)
 			goto err_free;
 		blkg->pd[i] = pd;
 		pd->blkg = blkg;
 		pd->plid = i;
 	}
 	return blkg;
 err_free:
 	blkg_free(blkg);
 	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.
  */
 struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
 			       bool update_hint)
 {
 	struct blkcg_gq *blkg;
 	blkg = rcu_dereference(blkcg->blkg_hint);
 	if (blkg && blkg->q == q)
 		return blkg;
 	/*
 	 * 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 (update_hint) {
 			lockdep_assert_held(q->queue_lock);
 			rcu_assign_pointer(blkcg->blkg_hint, blkg);
 		}
 		return blkg;
 	}
 	return NULL;
 }
 /**
  * blkg_lookup - lookup blkg for the specified blkcg - q pair
  * @blkcg: blkcg of interest
  * @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.
  */
 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);
 }
 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_create(struct blkcg *blkcg,
 				    struct request_queue *q,
 				    struct blkcg_gq *new_blkg)
 {
 	struct blkcg_gq *blkg;
 	int i, ret;
 	WARN_ON_ONCE(!rcu_read_lock_held());
 	lockdep_assert_held(q->queue_lock);
 	/* blkg holds a reference to blkcg */
 	if (!css_tryget(&blkcg->css)) {
 		ret = -EINVAL;
 		goto err_free_blkg;
 	}
 	/* allocate */
 	if (!new_blkg) {
 		new_blkg = blkg_alloc(blkcg, q, GFP_ATOMIC);
 		if (unlikely(!new_blkg)) {
 			ret = -ENOMEM;
 			goto err_put_css;
 		}
 	}
 	blkg = new_blkg;
 	/* link parent */
 	if (blkcg_parent(blkcg)) {
 		blkg->parent = __blkg_lookup(blkcg_parent(blkcg), q, false);
 		if (WARN_ON_ONCE(!blkg->parent)) {
 			ret = -EINVAL;
 			goto err_put_css;
 		}
 		blkg_get(blkg->parent);
 	}
 	/* invoke per-policy init */
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
 		if (blkg->pd[i] && pol->pd_init_fn)
 			pol->pd_init_fn(blkg);
 	}
 	/* insert */
 	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 failed fully initialized, use the usual release path */
 	blkg_put(blkg);
 	return ERR_PTR(ret);
 err_put_css:
 	css_put(&blkcg->css);
 err_free_blkg:
 	blkg_free(new_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);
 	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);
 	/* Something wrong if we are trying to remove same group twice */
 	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);
 	/*
 	 * Both setting lookup hint to and clearing it from @blkg are done
 	 * under queue_lock.  If it's not pointing to @blkg now, it never
 	 * will.  Hint assignment itself can race safely.
 	 */
 	if (rcu_dereference_raw(blkcg->blkg_hint) == blkg)
 		rcu_assign_pointer(blkcg->blkg_hint, NULL);
 	/*
 	 * Put the reference taken at the time of creation so that when all
 	 * queues are gone, group can be destroyed.
 	 */
 	blkg_put(blkg);
 }
 /**
  * blkg_destroy_all - destroy all blkgs associated with a request_queue
  * @q: request_queue of interest
  *
  * Destroy all blkgs associated with @q.
  */
 static void blkg_destroy_all(struct request_queue *q)
 {
 	struct blkcg_gq *blkg, *n;
 	lockdep_assert_held(q->queue_lock);
 	list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) {
 		struct blkcg *blkcg = blkg->blkcg;
 		spin_lock(&blkcg->lock);
 		blkg_destroy(blkg);
 		spin_unlock(&blkcg->lock);
 	}
 	/*
 	 * root blkg is destroyed.  Just clear the pointer since
 	 * root_rl does not take reference on root blkg.
 	 */
 	q->root_blkg = NULL;
 	q->root_rl.blkg = NULL;
 }
-static void blkg_rcu_free(struct rcu_head *rcu_head)
+/*
+ * A group is RCU protected, but having an rcu lock does not mean that one
+ * can access all the fields of blkg and assume these are valid.  For
+ * example, don't try to follow throtl_data and request queue links.
+ *
+ * Having a reference to blkg under an rcu allows accesses to only values
+ * local to groups like group stats and group rate limits.
+ */
+void __blkg_release_rcu(struct rcu_head *rcu_head)
 {
-	blkg_free(container_of(rcu_head, struct blkcg_gq, rcu_head));
+	struct blkcg_gq *blkg = container_of(rcu_head, struct blkcg_gq, rcu_head);
-}
-void __blkg_release(struct blkcg_gq *blkg)
-{
 	int i;
 	/* tell policies that this one is being freed */
 	for (i = 0; i < BLKCG_MAX_POLS; i++) {
 		struct blkcg_policy *pol = blkcg_policy[i];
 		if (blkg->pd[i] && pol->pd_exit_fn)
 			pol->pd_exit_fn(blkg);
 	}
 	/* release the blkcg and parent blkg refs this blkg has been holding */
 	css_put(&blkg->blkcg->css);
-	if (blkg->parent)
+	if (blkg->parent) {
+		spin_lock_irq(blkg->q->queue_lock);
 		blkg_put(blkg->parent);
+		spin_unlock_irq(blkg->q->queue_lock);
+	}
-	/*
+	blkg_free(blkg);
-	 * A group is freed in rcu manner. But having an rcu lock does not
-	 * mean that one can access all the fields of blkg and assume these
-	 * are valid. For example, don't try to follow throtl_data and
-	 * request queue links.
-	 *
-	 * Having a reference to blkg under an rcu allows acess to only
-	 * values local to groups like group stats and group rate limits
-	 */
-	call_rcu(&blkg->rcu_head, blkg_rcu_free);
 }
-EXPORT_SYMBOL_GPL(__blkg_release);
+EXPORT_SYMBOL_GPL(__blkg_release_rcu);
 /*
  * The next function used by blk_queue_for_each_rl().  It's a bit tricky
  * because the root blkg uses @q->root_rl instead of its own rl.
  */
 struct request_list *__blk_queue_next_rl(struct request_list *rl,
 					 struct request_queue *q)
 {
 	struct list_head *ent;
 	struct blkcg_gq *blkg;
 	/*
 	 * Determine the current blkg list_head.  The first entry is
 	 * root_rl which is off @q->blkg_list and mapped to the head.
 	 */
 	if (rl == &q->root_rl) {
 		ent = &q->blkg_list;
 		/* There are no more block groups, hence no request lists */
 		if (list_empty(ent))
 			return NULL;
 	} else {
 		blkg = container_of(rl, struct blkcg_gq, rl);
 		ent = &blkg->q_node;
 	}
 	/* walk to the next list_head, skip root blkcg */
 	ent = ent->next;
 	if (ent == &q->root_blkg->q_node)
 		ent = ent->next;
 	if (ent == &q->blkg_list)
 		return NULL;
 	blkg = container_of(ent, struct blkcg_gq, q_node);
 	return &blkg->rl;
 }
 static int blkcg_reset_stats(struct cgroup *cgroup, struct cftype *cftype,
 			     u64 val)
 {
 	struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
 	struct blkcg_gq *blkg;
 	int i;
 	mutex_lock(&blkcg_pol_mutex);
 	spin_lock_irq(&blkcg->lock);
 	/*
 	 * Note that stat reset is racy - it doesn't synchronize against
 	 * stat updates.  This is a debug feature which shouldn't exist
 	 * anyway.  If you get hit by a race, retry.
 	 */
 	hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
 		for (i = 0; i < BLKCG_MAX_POLS; i++) {
 			struct blkcg_policy *pol = blkcg_policy[i];
 			if (blkcg_policy_enabled(blkg->q, pol) &&
 			    pol->pd_reset_stats_fn)
 				pol->pd_reset_stats_fn(blkg);
 		}
 	}
 	spin_unlock_irq(&blkcg->lock);
 	mutex_unlock(&blkcg_pol_mutex);
 	return 0;
 }
 static const char *blkg_dev_name(struct blkcg_gq *blkg)
 {
 	/* some drivers (floppy) instantiate a queue w/o disk registered */
 	if (blkg->q->backing_dev_info.dev)
 		return dev_name(blkg->q->backing_dev_info.dev);
 	return NULL;
 }
 /**
  * blkcg_print_blkgs - helper for printing per-blkg data
  * @sf: seq_file to print to
  * @blkcg: blkcg of interest
  * @prfill: fill function to print out a blkg
  * @pol: policy in question
  * @data: data to be passed to @prfill
  * @show_total: to print out sum of prfill return values or not
  *
  * 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 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.
  */
 void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
 		       u64 (*prfill)(struct seq_file *,
 				     struct blkg_policy_data *, int),
 		       const struct blkcg_policy *pol, int data,
 		       bool show_total)
 {
 	struct blkcg_gq *blkg;
 	u64 total = 0;
 	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(blkg->q->queue_lock);
 	}
 	rcu_read_unlock();
 	if (show_total)
 		seq_printf(sf, "Total %llu\n", (unsigned long long)total);
 }
 EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
 /**
  * __blkg_prfill_u64 - prfill helper for a single u64 value
  * @sf: seq_file to print to
  * @pd: policy private data of interest
  * @v: value to print
  *
  * Print @v to @sf for the device assocaited with @pd.
  */
 u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
 {
 	const char *dname = blkg_dev_name(pd->blkg);
 	if (!dname)
 		return 0;
 	seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
 	return v;
 }
 EXPORT_SYMBOL_GPL(__blkg_prfill_u64);
 /**
  * __blkg_prfill_rwstat - prfill helper for a blkg_rwstat
  * @sf: seq_file to print to
  * @pd: policy private data of interest
  * @rwstat: rwstat to print
  *
  * Print @rwstat to @sf for the device assocaited with @pd.
  */
 u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 			 const struct blkg_rwstat *rwstat)
 {
 	static const char *rwstr[] = {
 		[BLKG_RWSTAT_READ]	= "Read",
 		[BLKG_RWSTAT_WRITE]	= "Write",
 		[BLKG_RWSTAT_SYNC]	= "Sync",
 		[BLKG_RWSTAT_ASYNC]	= "Async",
 	};
 	const char *dname = blkg_dev_name(pd->blkg);
 	u64 v;
 	int i;
 	if (!dname)
 		return 0;
 	for (i = 0; i < BLKG_RWSTAT_NR; i++)
 		seq_printf(sf, "%s %s %llu\n", dname, rwstr[i],
 			   (unsigned long long)rwstat->cnt[i]);
 	v = rwstat->cnt[BLKG_RWSTAT_READ] + rwstat->cnt[BLKG_RWSTAT_WRITE];
 	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
  * @sf: seq_file to print to
  * @pd: policy private data of interest
  * @off: offset to the blkg_stat in @pd
  *
  * prfill callback for printing a blkg_stat.
  */
 u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off)
 {
 	return __blkg_prfill_u64(sf, pd, blkg_stat_read((void *)pd + off));
 }
 EXPORT_SYMBOL_GPL(blkg_prfill_stat);
 /**
  * blkg_prfill_rwstat - prfill callback for blkg_rwstat
  * @sf: seq_file to print to
  * @pd: policy private data of interest
  * @off: offset to the blkg_rwstat in @pd
  *
  * prfill callback for printing a blkg_rwstat.
  */
 u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
 		       int off)
 {
 	struct blkg_rwstat rwstat = blkg_rwstat_read((void *)pd + off);
 	return __blkg_prfill_rwstat(sf, pd, &rwstat);
 }
 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
  * @input: input string
  * @ctx: blkg_conf_ctx to be filled
  *
  * Parse per-blkg config update from @input and initialize @ctx with the
  * result.  @ctx->blkg points to the blkg to be updated and @ctx->v the new
  * value.  This function returns with RCU read lock and queue lock held and
  * must be paired with blkg_conf_finish().
  */
 int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		   const char *input, struct blkg_conf_ctx *ctx)
 	__acquires(rcu) __acquires(disk->queue->queue_lock)
 {
 	struct gendisk *disk;
 	struct blkcg_gq *blkg;
 	unsigned int major, minor;
 	unsigned long long v;
 	int part, ret;
 	if (sscanf(input, "%u:%u %llu", &major, &minor, &v) != 3)
 		return -EINVAL;
 	disk = get_gendisk(MKDEV(major, minor), &part);
 	if (!disk || part)
 		return -EINVAL;
 	rcu_read_lock();
 	spin_lock_irq(disk->queue->queue_lock);
 	if (blkcg_policy_enabled(disk->queue, pol))
 		blkg = blkg_lookup_create(blkcg, disk->queue);
 	else
 		blkg = ERR_PTR(-EINVAL);
 	if (IS_ERR(blkg)) {
 		ret = PTR_ERR(blkg);
 		rcu_read_unlock();
 		spin_unlock_irq(disk->queue->queue_lock);
 		put_disk(disk);
 		/*
 		 * If queue was bypassing, we should retry.  Do so after a
 		 * short msleep().  It isn't strictly necessary but queue
 		 * can be bypassing for some time and it's always nice to
 		 * avoid busy looping.
 		 */
 		if (ret == -EBUSY) {
 			msleep(10);
 			ret = restart_syscall();
 		}
 		return ret;
 	}
 	ctx->disk = disk;
 	ctx->blkg = blkg;
 	ctx->v = v;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(blkg_conf_prep);
 /**
  * blkg_conf_finish - finish up per-blkg config update
  * @ctx: blkg_conf_ctx intiailized by blkg_conf_prep()
  *
  * Finish up after per-blkg config update.  This function must be paired
  * with blkg_conf_prep().
  */
 void blkg_conf_finish(struct blkg_conf_ctx *ctx)
 	__releases(ctx->disk->queue->queue_lock) __releases(rcu)
 {
 	spin_unlock_irq(ctx->disk->queue->queue_lock);
 	rcu_read_unlock();
 	put_disk(ctx->disk);
 }
 EXPORT_SYMBOL_GPL(blkg_conf_finish);
 struct cftype blkcg_files[] = {
 	{
 		.name = "reset_stats",
 		.write_u64 = blkcg_reset_stats,
 	},
 	{ }	/* terminate */
 };
 /**
  * blkcg_css_offline - cgroup css_offline callback
  * @cgroup: cgroup of interest
  *
  * This function is called when @cgroup is about to go away and responsible
  * for shooting down all blkgs associated with @cgroup.  blkgs should be
  * removed while holding both q and blkcg locks.  As blkcg lock is nested
  * inside q lock, this function performs reverse double lock dancing.
  *
  * This is the blkcg counterpart of ioc_release_fn().
  */
 static void blkcg_css_offline(struct cgroup *cgroup)
 {
 	struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
 	spin_lock_irq(&blkcg->lock);
 	while (!hlist_empty(&blkcg->blkg_list)) {
 		struct blkcg_gq *blkg = hlist_entry(blkcg->blkg_list.first,
 						struct blkcg_gq, blkcg_node);
 		struct request_queue *q = blkg->q;
 		if (spin_trylock(q->queue_lock)) {
 			blkg_destroy(blkg);
 			spin_unlock(q->queue_lock);
 		} else {
 			spin_unlock_irq(&blkcg->lock);
 			cpu_relax();
 			spin_lock_irq(&blkcg->lock);
 		}
 	}
 	spin_unlock_irq(&blkcg->lock);
 }
 static void blkcg_css_free(struct cgroup *cgroup)
 {
 	struct blkcg *blkcg = cgroup_to_blkcg(cgroup);
 	if (blkcg != &blkcg_root)
 		kfree(blkcg);
 }
 static struct cgroup_subsys_state *blkcg_css_alloc(struct cgroup *cgroup)
 {
 	static atomic64_t id_seq = ATOMIC64_INIT(0);
 	struct blkcg *blkcg;
 	struct cgroup *parent = cgroup->parent;
 	if (!parent) {
 		blkcg = &blkcg_root;
 		goto done;
 	}
 	blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
 	if (!blkcg)
 		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);
 	INIT_RADIX_TREE(&blkcg->blkg_tree, GFP_ATOMIC);
 	INIT_HLIST_HEAD(&blkcg->blkg_list);
 	return &blkcg->css;
 }
 /**
  * blkcg_init_queue - initialize blkcg part of request queue
  * @q: request_queue to initialize
  *
  * Called from blk_alloc_queue_node(). Responsible for initializing blkcg
  * part of new request_queue @q.
  *
  * RETURNS:
  * 0 on success, -errno on failure.
  */
 int blkcg_init_queue(struct request_queue *q)
 {
 	might_sleep();
 	return blk_throtl_init(q);
 }
 /**
  * blkcg_drain_queue - drain blkcg part of request_queue
  * @q: request_queue to drain
  *
  * Called from blk_drain_queue().  Responsible for draining blkcg part.
  */
 void blkcg_drain_queue(struct request_queue *q)
 {
 	lockdep_assert_held(q->queue_lock);
 	blk_throtl_drain(q);
 }
 /**
  * blkcg_exit_queue - exit and release blkcg part of request_queue
  * @q: request_queue being released
  *
  * Called from blk_release_queue().  Responsible for exiting blkcg part.
  */
 void blkcg_exit_queue(struct request_queue *q)
 {
 	spin_lock_irq(q->queue_lock);
 	blkg_destroy_all(q);
 	spin_unlock_irq(q->queue_lock);
 	blk_throtl_exit(q);
 }
 /*
  * We cannot support shared io contexts, as we have no mean to support
  * two tasks with the same ioc in two different groups without major rework
  * of the main cic data structures.  For now we allow a task to change
  * its cgroup only if it's the only owner of its ioc.
  */
 static int blkcg_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 {
 	struct task_struct *task;
 	struct io_context *ioc;
 	int ret = 0;
 	/* task_lock() is needed to avoid races with exit_io_context() */
 	cgroup_taskset_for_each(task, cgrp, tset) {
 		task_lock(task);
 		ioc = task->io_context;
 		if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 			ret = -EINVAL;
 		task_unlock(task);
 		if (ret)
 			break;
 	}
 	return ret;
 }
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.css_alloc = blkcg_css_alloc,
 	.css_offline = blkcg_css_offline,
 	.css_free = blkcg_css_free,
 	.can_attach = blkcg_can_attach,
 	.subsys_id = blkio_subsys_id,
 	.base_cftypes = blkcg_files,
 	.module = THIS_MODULE,
 	/*
 	 * blkio subsystem is utterly broken in terms of hierarchy support.
 	 * It treats all cgroups equally regardless of where they're
 	 * located in the hierarchy - all cgroups are treated as if they're
 	 * right below the root.  Fix it and remove the following.
 	 */
 	.broken_hierarchy = true,
 };
 EXPORT_SYMBOL_GPL(blkio_subsys);
 /**
  * blkcg_activate_policy - activate a blkcg policy on a request_queue
  * @q: request_queue of interest
  * @pol: blkcg policy to activate
  *
  * Activate @pol on @q.  Requires %GFP_KERNEL context.  @q goes through
  * bypass mode to populate its blkgs with policy_data for @pol.
  *
  * Activation happens with @q bypassed, so nobody would be accessing blkgs
  * from IO path.  Update of each blkg is protected by both queue and blkcg
  * locks so that holding either lock and testing blkcg_policy_enabled() is
  * always enough for dereferencing policy data.
  *
  * The caller is responsible for synchronizing [de]activations and policy
  * [un]registerations.  Returns 0 on success, -errno on failure.
  */
 int blkcg_activate_policy(struct request_queue *q,
 			  const struct blkcg_policy *pol)
 {
 	LIST_HEAD(pds);
 	struct blkcg_gq *blkg, *new_blkg;
 	struct blkg_policy_data *pd, *n;
 	int cnt = 0, ret;
 	bool preloaded;
 	if (blkcg_policy_enabled(q, pol))
 		return 0;
 	/* preallocations for root blkg */
 	new_blkg = blkg_alloc(&blkcg_root, q, GFP_KERNEL);
 	if (!new_blkg)
 		return -ENOMEM;
 	blk_queue_bypass_start(q);
 	preloaded = !radix_tree_preload(GFP_KERNEL);
 	/*
 	 * 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(&blkcg_root, q, false);
 	if (blkg)
 		blkg_free(new_blkg);
 	else
 		blkg = blkg_create(&blkcg_root, q, new_blkg);
 	rcu_read_unlock();
 	if (preloaded)
 		radix_tree_preload_end();
 	if (IS_ERR(blkg)) {
 		ret = PTR_ERR(blkg);
 		goto out_unlock;
 	}
 	q->root_blkg = blkg;
 	q->root_rl.blkg = blkg;
 	list_for_each_entry(blkg, &q->blkg_list, q_node)
 		cnt++;
 	spin_unlock_irq(q->queue_lock);
 	/* allocate policy_data for all existing blkgs */
 	while (cnt--) {
 		pd = kzalloc_node(pol->pd_size, GFP_KERNEL, q->node);
 		if (!pd) {
 			ret = -ENOMEM;
 			goto out_free;
 		}
 		list_add_tail(&pd->alloc_node, &pds);
 	}
 	/*
 	 * Install the allocated pds.  With @q bypassing, no new blkg
 	 * should have been created while the queue lock was dropped.
 	 */
 	spin_lock_irq(q->queue_lock);
 	list_for_each_entry(blkg, &q->blkg_list, q_node) {
 		if (WARN_ON(list_empty(&pds))) {
 			/* umm... this shouldn't happen, just abort */
 			ret = -ENOMEM;
 			goto out_unlock;
 		}
 		pd = list_first_entry(&pds, struct blkg_policy_data, alloc_node);
 		list_del_init(&pd->alloc_node);
 		/* grab blkcg lock too while installing @pd on @blkg */
 		spin_lock(&blkg->blkcg->lock);
 		blkg->pd[pol->plid] = pd;
 		pd->blkg = blkg;
 		pd->plid = pol->plid;
 		pol->pd_init_fn(blkg);
 		spin_unlock(&blkg->blkcg->lock);
 	}
 	__set_bit(pol->plid, q->blkcg_pols);
 	ret = 0;
 out_unlock:
 	spin_unlock_irq(q->queue_lock);
 out_free:
 	blk_queue_bypass_end(q);
 	list_for_each_entry_safe(pd, n, &pds, alloc_node)
 		kfree(pd);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blkcg_activate_policy);
 /**
  * blkcg_deactivate_policy - deactivate a blkcg policy on a request_queue
  * @q: request_queue of interest
  * @pol: blkcg policy to deactivate
  *
  * Deactivate @pol on @q.  Follows the same synchronization rules as
  * blkcg_activate_policy().
  */
 void blkcg_deactivate_policy(struct request_queue *q,
 			     const struct blkcg_policy *pol)
 {
 	struct blkcg_gq *blkg;
 	if (!blkcg_policy_enabled(q, pol))
 		return;
 	blk_queue_bypass_start(q);
 	spin_lock_irq(q->queue_lock);
 	__clear_bit(pol->plid, q->blkcg_pols);
 	/* if no policy is left, no need for blkgs - shoot them down */
 	if (bitmap_empty(q->blkcg_pols, BLKCG_MAX_POLS))
 		blkg_destroy_all(q);
 	list_for_each_entry(blkg, &q->blkg_list, q_node) {
 		/* 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);
 		kfree(blkg->pd[pol->plid]);
 		blkg->pd[pol->plid] = NULL;
 		spin_unlock(&blkg->blkcg->lock);
 	}
 	spin_unlock_irq(q->queue_lock);
 	blk_queue_bypass_end(q);
 }
 EXPORT_SYMBOL_GPL(blkcg_deactivate_policy);
 /**
  * blkcg_policy_register - register a blkcg policy
  * @pol: blkcg policy to register
  *
  * Register @pol with blkcg core.  Might sleep and @pol may be modified on
  * successful registration.  Returns 0 on success and -errno on failure.
  */
 int blkcg_policy_register(struct blkcg_policy *pol)
 {
 	int i, ret;
 	if (WARN_ON(pol->pd_size < sizeof(struct blkg_policy_data)))
 		return -EINVAL;
 	mutex_lock(&blkcg_pol_mutex);
 	/* find an empty slot */
 	ret = -ENOSPC;
 	for (i = 0; i < BLKCG_MAX_POLS; i++)
 		if (!blkcg_policy[i])
 			break;
 	if (i >= BLKCG_MAX_POLS)
 		goto out_unlock;
 	/* register and update blkgs */
 	pol->plid = i;
 	blkcg_policy[i] = pol;
 	/* everything is in place, add intf files for the new policy */
 	if (pol->cftypes)
 		WARN_ON(cgroup_add_cftypes(&blkio_subsys, pol->cftypes));
 	ret = 0;
 out_unlock:
 	mutex_unlock(&blkcg_pol_mutex);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(blkcg_policy_register);
 /**
  * blkcg_policy_unregister - unregister a blkcg policy
  * @pol: blkcg policy to unregister
  *
  * Undo blkcg_policy_register(@pol).  Might sleep.
  */
 void blkcg_policy_unregister(struct blkcg_policy *pol)
 {
 	mutex_lock(&blkcg_pol_mutex);
 	if (WARN_ON(blkcg_policy[pol->plid] != pol))
 		goto out_unlock;

block/blk-cgroup.h

Diff comments View file @ 2a4fd07

1	#ifndef _BLK_CGROUP_H	1	#ifndef _BLK_CGROUP_H
2	#define _BLK_CGROUP_H	2	#define _BLK_CGROUP_H
3	/*	3	/*
4	* Common Block IO controller cgroup interface	4	* Common Block IO controller cgroup interface
5	*	5	*
6	* Based on ideas and code from CFQ, CFS and BFQ:	6	* Based on ideas and code from CFQ, CFS and BFQ:
7	* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>	7	* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
8	*	8	*
9	* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>	9	* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
10	* Paolo Valente <paolo.valente@unimore.it>	10	* Paolo Valente <paolo.valente@unimore.it>
11	*	11	*
12	* Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>	12	* Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
13	* Nauman Rafique <nauman@google.com>	13	* Nauman Rafique <nauman@google.com>
14	*/	14	*/
15		15
16	#include <linux/cgroup.h>	16	#include <linux/cgroup.h>
17	#include <linux/u64_stats_sync.h>	17	#include <linux/u64_stats_sync.h>
18	#include <linux/seq_file.h>	18	#include <linux/seq_file.h>
19	#include <linux/radix-tree.h>	19	#include <linux/radix-tree.h>
20	#include <linux/blkdev.h>	20	#include <linux/blkdev.h>
21		21
22	/* Max limits for throttle policy */	22	/* Max limits for throttle policy */
23	#define THROTL_IOPS_MAX UINT_MAX	23	#define THROTL_IOPS_MAX UINT_MAX
24		24
25	/* CFQ specific, out here for blkcg->cfq_weight */	25	/* CFQ specific, out here for blkcg->cfq_weight */
26	#define CFQ_WEIGHT_MIN 10	26	#define CFQ_WEIGHT_MIN 10
27	#define CFQ_WEIGHT_MAX 1000	27	#define CFQ_WEIGHT_MAX 1000
28	#define CFQ_WEIGHT_DEFAULT 500	28	#define CFQ_WEIGHT_DEFAULT 500
29		29
30	#ifdef CONFIG_BLK_CGROUP	30	#ifdef CONFIG_BLK_CGROUP
31		31
32	enum blkg_rwstat_type {	32	enum blkg_rwstat_type {
33	BLKG_RWSTAT_READ,	33	BLKG_RWSTAT_READ,
34	BLKG_RWSTAT_WRITE,	34	BLKG_RWSTAT_WRITE,
35	BLKG_RWSTAT_SYNC,	35	BLKG_RWSTAT_SYNC,
36	BLKG_RWSTAT_ASYNC,	36	BLKG_RWSTAT_ASYNC,
37		37
38	BLKG_RWSTAT_NR,	38	BLKG_RWSTAT_NR,
39	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,	39	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
40	};	40	};