diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index cf9247301e3cebd75236402c9aadcd75c4d49f06..95a19d1fbedf943acdd635e5407d5f0342211f2c 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -565,26 +565,134 @@ static struct request *bfq_choose_req(struct bfq_data *bfqd,
}
}
+#define BFQ_LIMIT_INLINE_DEPTH 16
+
+#ifdef CONFIG_BFQ_GROUP_IOSCHED
+static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit)
+{
+ struct bfq_data *bfqd = bfqq->bfqd;
+ struct bfq_entity *entity = &bfqq->entity;
+ struct bfq_entity *inline_entities[BFQ_LIMIT_INLINE_DEPTH];
+ struct bfq_entity **entities = inline_entities;
+ int depth, level;
+ int class_idx = bfqq->ioprio_class - 1;
+ struct bfq_sched_data *sched_data;
+ unsigned long wsum;
+ bool ret = false;
+
+ if (!entity->on_st_or_in_serv)
+ return false;
+
+ /* +1 for bfqq entity, root cgroup not included */
+ depth = bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css.cgroup->level + 1;
+ if (depth > BFQ_LIMIT_INLINE_DEPTH) {
+ entities = kmalloc_array(depth, sizeof(*entities), GFP_NOIO);
+ if (!entities)
+ return false;
+ }
+
+ spin_lock_irq(&bfqd->lock);
+ sched_data = entity->sched_data;
+ /* Gather our ancestors as we need to traverse them in reverse order */
+ level = 0;
+ for_each_entity(entity) {
+ /*
+ * If at some level entity is not even active, allow request
+ * queueing so that BFQ knows there's work to do and activate
+ * entities.
+ */
+ if (!entity->on_st_or_in_serv)
+ goto out;
+ /* Uh, more parents than cgroup subsystem thinks? */
+ if (WARN_ON_ONCE(level >= depth))
+ break;
+ entities[level++] = entity;
+ }
+ WARN_ON_ONCE(level != depth);
+ for (level--; level >= 0; level--) {
+ entity = entities[level];
+ if (level > 0) {
+ wsum = bfq_entity_service_tree(entity)->wsum;
+ } else {
+ int i;
+ /*
+ * For bfqq itself we take into account service trees
+ * of all higher priority classes and multiply their
+ * weights so that low prio queue from higher class
+ * gets more requests than high prio queue from lower
+ * class.
+ */
+ wsum = 0;
+ for (i = 0; i <= class_idx; i++) {
+ wsum = wsum * IOPRIO_BE_NR +
+ sched_data->service_tree[i].wsum;
+ }
+ }
+ limit = DIV_ROUND_CLOSEST(limit * entity->weight, wsum);
+ if (entity->allocated >= limit) {
+ bfq_log_bfqq(bfqq->bfqd, bfqq,
+ "too many requests: allocated %d limit %d level %d",
+ entity->allocated, limit, level);
+ ret = true;
+ break;
+ }
+ }
+out:
+ spin_unlock_irq(&bfqd->lock);
+ if (entities != inline_entities)
+ kfree(entities);
+ return ret;
+}
+#else
+static bool bfqq_request_over_limit(struct bfq_queue *bfqq, int limit)
+{
+ return false;
+}
+#endif
+
/*
* Async I/O can easily starve sync I/O (both sync reads and sync
* writes), by consuming all tags. Similarly, storms of sync writes,
* such as those that sync(2) may trigger, can starve sync reads.
* Limit depths of async I/O and sync writes so as to counter both
* problems.
+ *
+ * Also if a bfq queue or its parent cgroup consume more tags than would be
+ * appropriate for their weight, we trim the available tag depth to 1. This
+ * avoids a situation where one cgroup can starve another cgroup from tags and
+ * thus block service differentiation among cgroups. Note that because the
+ * queue / cgroup already has many requests allocated and queued, this does not
+ * significantly affect service guarantees coming from the BFQ scheduling
+ * algorithm.
*/
static void bfq_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
{
struct bfq_data *bfqd = data->q->elevator->elevator_data;
+ struct bfq_io_cq *bic = icq_to_bic(blk_mq_sched_get_icq(data->q));
+ struct bfq_queue *bfqq = bic ? bic_to_bfqq(bic, op_is_sync(op)) : NULL;
+ int depth;
+ unsigned limit = data->q->nr_requests;
+
+ /* Sync reads have full depth available */
+ if (op_is_sync(op) && !op_is_write(op)) {
+ depth = 0;
+ } else {
+ depth = bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)];
+ limit = (limit * depth) >> bfqd->full_depth_shift;
+ }
- if (op_is_sync(op) && !op_is_write(op))
- return;
-
- data->shallow_depth =
- bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)];
+ /*
+ * Does queue (or any parent entity) exceed number of requests that
+ * should be available to it? Heavily limit depth so that it cannot
+ * consume more available requests and thus starve other entities.
+ */
+ if (bfqq && bfqq_request_over_limit(bfqq, limit))
+ depth = 1;
bfq_log(bfqd, "[%s] wr_busy %d sync %d depth %u",
- __func__, bfqd->wr_busy_queues, op_is_sync(op),
- data->shallow_depth);
+ __func__, bfqd->wr_busy_queues, op_is_sync(op), depth);
+ if (depth)
+ data->shallow_depth = depth;
}
static struct bfq_queue *
@@ -6853,10 +6961,8 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
* See the comments on bfq_limit_depth for the purpose of
* the depths set in the function. Return minimum shallow depth we'll use.
*/
-static unsigned int bfq_update_depths(struct bfq_data *bfqd,
- struct sbitmap_queue *bt)
+static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
{
- unsigned int i, j, min_shallow = UINT_MAX;
unsigned int depth = 1U << bt->sb.shift;
bfqd->full_depth_shift = bt->sb.shift;
@@ -6890,22 +6996,15 @@ static unsigned int bfq_update_depths(struct bfq_data *bfqd,
bfqd->word_depths[1][0] = max((depth * 3) >> 4, 1U);
/* no more than ~37% of tags for sync writes (~20% extra tags) */
bfqd->word_depths[1][1] = max((depth * 6) >> 4, 1U);
-
- for (i = 0; i < 2; i++)
- for (j = 0; j < 2; j++)
- min_shallow = min(min_shallow, bfqd->word_depths[i][j]);
-
- return min_shallow;
}
static void bfq_depth_updated(struct blk_mq_hw_ctx *hctx)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
struct blk_mq_tags *tags = hctx->sched_tags;
- unsigned int min_shallow;
- min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags);
- sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
+ bfq_update_depths(bfqd, &tags->bitmap_tags);
+ sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, 1);
}
static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)