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-rw-r--r--drivers/md/dm-cache-background-tracker.c257
1 files changed, 257 insertions, 0 deletions
diff --git a/drivers/md/dm-cache-background-tracker.c b/drivers/md/dm-cache-background-tracker.c
new file mode 100644
index 000000000..c606e6bfc
--- /dev/null
+++ b/drivers/md/dm-cache-background-tracker.c
@@ -0,0 +1,257 @@
+/*
+ * Copyright (C) 2017 Red Hat. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm-cache-background-tracker.h"
+
+/*----------------------------------------------------------------*/
+
+#define DM_MSG_PREFIX "dm-background-tracker"
+
+struct bt_work {
+ struct list_head list;
+ struct rb_node node;
+ struct policy_work work;
+};
+
+struct background_tracker {
+ unsigned int max_work;
+ atomic_t pending_promotes;
+ atomic_t pending_writebacks;
+ atomic_t pending_demotes;
+
+ struct list_head issued;
+ struct list_head queued;
+ struct rb_root pending;
+
+ struct kmem_cache *work_cache;
+};
+
+struct background_tracker *btracker_create(unsigned int max_work)
+{
+ struct background_tracker *b = kmalloc(sizeof(*b), GFP_KERNEL);
+
+ if (!b) {
+ DMERR("couldn't create background_tracker");
+ return NULL;
+ }
+
+ b->max_work = max_work;
+ atomic_set(&b->pending_promotes, 0);
+ atomic_set(&b->pending_writebacks, 0);
+ atomic_set(&b->pending_demotes, 0);
+
+ INIT_LIST_HEAD(&b->issued);
+ INIT_LIST_HEAD(&b->queued);
+
+ b->pending = RB_ROOT;
+ b->work_cache = KMEM_CACHE(bt_work, 0);
+ if (!b->work_cache) {
+ DMERR("couldn't create mempool for background work items");
+ kfree(b);
+ b = NULL;
+ }
+
+ return b;
+}
+EXPORT_SYMBOL_GPL(btracker_create);
+
+void btracker_destroy(struct background_tracker *b)
+{
+ struct bt_work *w, *tmp;
+
+ BUG_ON(!list_empty(&b->issued));
+ list_for_each_entry_safe (w, tmp, &b->queued, list) {
+ list_del(&w->list);
+ kmem_cache_free(b->work_cache, w);
+ }
+
+ kmem_cache_destroy(b->work_cache);
+ kfree(b);
+}
+EXPORT_SYMBOL_GPL(btracker_destroy);
+
+static int cmp_oblock(dm_oblock_t lhs, dm_oblock_t rhs)
+{
+ if (from_oblock(lhs) < from_oblock(rhs))
+ return -1;
+
+ if (from_oblock(rhs) < from_oblock(lhs))
+ return 1;
+
+ return 0;
+}
+
+static bool __insert_pending(struct background_tracker *b,
+ struct bt_work *nw)
+{
+ int cmp;
+ struct bt_work *w;
+ struct rb_node **new = &b->pending.rb_node, *parent = NULL;
+
+ while (*new) {
+ w = container_of(*new, struct bt_work, node);
+
+ parent = *new;
+ cmp = cmp_oblock(w->work.oblock, nw->work.oblock);
+ if (cmp < 0)
+ new = &((*new)->rb_left);
+
+ else if (cmp > 0)
+ new = &((*new)->rb_right);
+
+ else
+ /* already present */
+ return false;
+ }
+
+ rb_link_node(&nw->node, parent, new);
+ rb_insert_color(&nw->node, &b->pending);
+
+ return true;
+}
+
+static struct bt_work *__find_pending(struct background_tracker *b,
+ dm_oblock_t oblock)
+{
+ int cmp;
+ struct bt_work *w;
+ struct rb_node **new = &b->pending.rb_node;
+
+ while (*new) {
+ w = container_of(*new, struct bt_work, node);
+
+ cmp = cmp_oblock(w->work.oblock, oblock);
+ if (cmp < 0)
+ new = &((*new)->rb_left);
+
+ else if (cmp > 0)
+ new = &((*new)->rb_right);
+
+ else
+ break;
+ }
+
+ return *new ? w : NULL;
+}
+
+
+static void update_stats(struct background_tracker *b, struct policy_work *w, int delta)
+{
+ switch (w->op) {
+ case POLICY_PROMOTE:
+ atomic_add(delta, &b->pending_promotes);
+ break;
+
+ case POLICY_DEMOTE:
+ atomic_add(delta, &b->pending_demotes);
+ break;
+
+ case POLICY_WRITEBACK:
+ atomic_add(delta, &b->pending_writebacks);
+ break;
+ }
+}
+
+unsigned int btracker_nr_writebacks_queued(struct background_tracker *b)
+{
+ return atomic_read(&b->pending_writebacks);
+}
+EXPORT_SYMBOL_GPL(btracker_nr_writebacks_queued);
+
+unsigned int btracker_nr_demotions_queued(struct background_tracker *b)
+{
+ return atomic_read(&b->pending_demotes);
+}
+EXPORT_SYMBOL_GPL(btracker_nr_demotions_queued);
+
+static bool max_work_reached(struct background_tracker *b)
+{
+ return atomic_read(&b->pending_promotes) +
+ atomic_read(&b->pending_writebacks) +
+ atomic_read(&b->pending_demotes) >= b->max_work;
+}
+
+static struct bt_work *alloc_work(struct background_tracker *b)
+{
+ if (max_work_reached(b))
+ return NULL;
+
+ return kmem_cache_alloc(b->work_cache, GFP_NOWAIT);
+}
+
+int btracker_queue(struct background_tracker *b,
+ struct policy_work *work,
+ struct policy_work **pwork)
+{
+ struct bt_work *w;
+
+ if (pwork)
+ *pwork = NULL;
+
+ w = alloc_work(b);
+ if (!w)
+ return -ENOMEM;
+
+ memcpy(&w->work, work, sizeof(*work));
+
+ if (!__insert_pending(b, w)) {
+ /*
+ * There was a race, we'll just ignore this second
+ * bit of work for the same oblock.
+ */
+ kmem_cache_free(b->work_cache, w);
+ return -EINVAL;
+ }
+
+ if (pwork) {
+ *pwork = &w->work;
+ list_add(&w->list, &b->issued);
+ } else
+ list_add(&w->list, &b->queued);
+ update_stats(b, &w->work, 1);
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(btracker_queue);
+
+/*
+ * Returns -ENODATA if there's no work.
+ */
+int btracker_issue(struct background_tracker *b, struct policy_work **work)
+{
+ struct bt_work *w;
+
+ if (list_empty(&b->queued))
+ return -ENODATA;
+
+ w = list_first_entry(&b->queued, struct bt_work, list);
+ list_move(&w->list, &b->issued);
+ *work = &w->work;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(btracker_issue);
+
+void btracker_complete(struct background_tracker *b,
+ struct policy_work *op)
+{
+ struct bt_work *w = container_of(op, struct bt_work, work);
+
+ update_stats(b, &w->work, -1);
+ rb_erase(&w->node, &b->pending);
+ list_del(&w->list);
+ kmem_cache_free(b->work_cache, w);
+}
+EXPORT_SYMBOL_GPL(btracker_complete);
+
+bool btracker_promotion_already_present(struct background_tracker *b,
+ dm_oblock_t oblock)
+{
+ return __find_pending(b, oblock) != NULL;
+}
+EXPORT_SYMBOL_GPL(btracker_promotion_already_present);
+
+/*----------------------------------------------------------------*/