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authorJustin TerAvest <teravest@google.com>2011-03-17 16:12:36 +0100
committerJens Axboe <jaxboe@fusionio.com>2011-03-17 16:12:36 +0100
commit8184f93eced1e304721c2a55c00d87d5a14f8907 (patch)
treeb5ed43533eee883bc25920c191cb095584d29822
parent95f28604a65b1c40b6c6cd95e58439cd7ded3add (diff)
downloadlinux-8184f93eced1e304721c2a55c00d87d5a14f8907.tar.bz2
cfq-iosched: Don't update group weights when on service tree
Version 3 is updated to apply to for-2.6.39/core. For version 2, I took Vivek's advice and made sure we update the group weight from cfq_group_service_tree_add(). If a weight was updated while a group is on the service tree, the calculation for the total weight of the service tree can be adjusted improperly, which either leads to bad service tree weights, or potentially crashes (if total_weight becomes 0). This patch defers updates to the weight until a group is off the service tree. Signed-off-by: Justin TerAvest <teravest@google.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
-rw-r--r--block/cfq-iosched.c53
1 files changed, 41 insertions, 12 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 89e0d1cc14ba..12e380b2c4e4 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -178,6 +178,8 @@ struct cfq_group {
/* group service_tree key */
u64 vdisktime;
unsigned int weight;
+ unsigned int new_weight;
+ bool needs_update;
/* number of cfqq currently on this group */
int nr_cfqq;
@@ -853,7 +855,27 @@ __cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
}
static void
-cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
+cfq_update_group_weight(struct cfq_group *cfqg)
+{
+ BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+ if (cfqg->needs_update) {
+ cfqg->weight = cfqg->new_weight;
+ cfqg->needs_update = false;
+ }
+}
+
+static void
+cfq_group_service_tree_add(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+ BUG_ON(!RB_EMPTY_NODE(&cfqg->rb_node));
+
+ cfq_update_group_weight(cfqg);
+ __cfq_group_service_tree_add(st, cfqg);
+ st->total_weight += cfqg->weight;
+}
+
+static void
+cfq_group_notify_queue_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
struct cfq_group *__cfqg;
@@ -874,13 +896,19 @@ cfq_group_service_tree_add(struct cfq_data *cfqd, struct cfq_group *cfqg)
cfqg->vdisktime = __cfqg->vdisktime + CFQ_IDLE_DELAY;
} else
cfqg->vdisktime = st->min_vdisktime;
+ cfq_group_service_tree_add(st, cfqg);
+}
- __cfq_group_service_tree_add(st, cfqg);
- st->total_weight += cfqg->weight;
+static void
+cfq_group_service_tree_del(struct cfq_rb_root *st, struct cfq_group *cfqg)
+{
+ st->total_weight -= cfqg->weight;
+ if (!RB_EMPTY_NODE(&cfqg->rb_node))
+ cfq_rb_erase(&cfqg->rb_node, st);
}
static void
-cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
+cfq_group_notify_queue_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
{
struct cfq_rb_root *st = &cfqd->grp_service_tree;
@@ -892,9 +920,7 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
return;
cfq_log_cfqg(cfqd, cfqg, "del_from_rr group");
- st->total_weight -= cfqg->weight;
- if (!RB_EMPTY_NODE(&cfqg->rb_node))
- cfq_rb_erase(&cfqg->rb_node, st);
+ cfq_group_service_tree_del(st, cfqg);
cfqg->saved_workload_slice = 0;
cfq_blkiocg_update_dequeue_stats(&cfqg->blkg, 1);
}
@@ -948,9 +974,10 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
charge = cfqq->allocated_slice;
/* Can't update vdisktime while group is on service tree */
- cfq_rb_erase(&cfqg->rb_node, st);
+ cfq_group_service_tree_del(st, cfqg);
cfqg->vdisktime += cfq_scale_slice(charge, cfqg);
- __cfq_group_service_tree_add(st, cfqg);
+ /* If a new weight was requested, update now, off tree */
+ cfq_group_service_tree_add(st, cfqg);
/* This group is being expired. Save the context */
if (time_after(cfqd->workload_expires, jiffies)) {
@@ -982,7 +1009,9 @@ static inline struct cfq_group *cfqg_of_blkg(struct blkio_group *blkg)
void cfq_update_blkio_group_weight(void *key, struct blkio_group *blkg,
unsigned int weight)
{
- cfqg_of_blkg(blkg)->weight = weight;
+ struct cfq_group *cfqg = cfqg_of_blkg(blkg);
+ cfqg->new_weight = weight;
+ cfqg->needs_update = true;
}
static struct cfq_group *
@@ -1255,7 +1284,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
service_tree->count++;
if ((add_front || !new_cfqq) && !group_changed)
return;
- cfq_group_service_tree_add(cfqd, cfqq->cfqg);
+ cfq_group_notify_queue_add(cfqd, cfqq->cfqg);
}
static struct cfq_queue *
@@ -1368,7 +1397,7 @@ static void cfq_del_cfqq_rr(struct cfq_data *cfqd, struct cfq_queue *cfqq)
cfqq->p_root = NULL;
}
- cfq_group_service_tree_del(cfqd, cfqq->cfqg);
+ cfq_group_notify_queue_del(cfqd, cfqq->cfqg);
BUG_ON(!cfqd->busy_queues);
cfqd->busy_queues--;
if (cfq_cfqq_sync(cfqq))