bcache in userspace; userspace fsck

1 files changed, 701 insertions, 0 deletions

diff --git a/libbcache/btree_cache.c b/libbcache/btree_cache.c
new file mode 100644
index 00000000..09941906
--- /dev/null
+++ b/libbcache/btree_cache.c
@@ -0,0 +1,701 @@
+
+#include "bcache.h"
+#include "btree_cache.h"
+#include "btree_io.h"
+#include "btree_iter.h"
+#include "btree_locking.h"
+#include "debug.h"
+#include "extents.h"
+
+#include <trace/events/bcache.h>
+
+#define DEF_BTREE_ID(kwd, val, name) name,
+
+const char *bch_btree_id_names[BTREE_ID_NR] = {
+	DEFINE_BCH_BTREE_IDS()
+};
+
+#undef DEF_BTREE_ID
+
+void bch_recalc_btree_reserve(struct cache_set *c)
+{
+	unsigned i, reserve = 16;
+
+	if (!c->btree_roots[0].b)
+		reserve += 8;
+
+	for (i = 0; i < BTREE_ID_NR; i++)
+		if (c->btree_roots[i].b)
+			reserve += min_t(unsigned, 1,
+					 c->btree_roots[i].b->level) * 8;
+
+	c->btree_cache_reserve = reserve;
+}
+
+#define mca_can_free(c)						\
+	max_t(int, 0, c->btree_cache_used - c->btree_cache_reserve)
+
+static void __mca_data_free(struct cache_set *c, struct btree *b)
+{
+	EBUG_ON(btree_node_write_in_flight(b));
+
+	free_pages((unsigned long) b->data, btree_page_order(c));
+	b->data = NULL;
+	bch_btree_keys_free(b);
+}
+
+static void mca_data_free(struct cache_set *c, struct btree *b)
+{
+	__mca_data_free(c, b);
+	c->btree_cache_used--;
+	list_move(&b->list, &c->btree_cache_freed);
+}
+
+#define PTR_HASH(_k)	(bkey_i_to_extent_c(_k)->v._data[0])
+
+static const struct rhashtable_params bch_btree_cache_params = {
+	.head_offset	= offsetof(struct btree, hash),
+	.key_offset	= offsetof(struct btree, key.v),
+	.key_len	= sizeof(struct bch_extent_ptr),
+};
+
+static void mca_data_alloc(struct cache_set *c, struct btree *b, gfp_t gfp)
+{
+	unsigned order = ilog2(btree_pages(c));
+
+	b->data = (void *) __get_free_pages(gfp, order);
+	if (!b->data)
+		goto err;
+
+	if (bch_btree_keys_alloc(b, order, gfp))
+		goto err;
+
+	c->btree_cache_used++;
+	list_move(&b->list, &c->btree_cache_freeable);
+	return;
+err:
+	free_pages((unsigned long) b->data, order);
+	b->data = NULL;
+	list_move(&b->list, &c->btree_cache_freed);
+}
+
+static struct btree *mca_bucket_alloc(struct cache_set *c, gfp_t gfp)
+{
+	struct btree *b = kzalloc(sizeof(struct btree), gfp);
+	if (!b)
+		return NULL;
+
+	six_lock_init(&b->lock);
+	INIT_LIST_HEAD(&b->list);
+	INIT_LIST_HEAD(&b->write_blocked);
+
+	mca_data_alloc(c, b, gfp);
+	return b->data ? b : NULL;
+}
+
+/* Btree in memory cache - hash table */
+
+void mca_hash_remove(struct cache_set *c, struct btree *b)
+{
+	BUG_ON(btree_node_dirty(b));
+
+	b->nsets = 0;
+
+	rhashtable_remove_fast(&c->btree_cache_table, &b->hash,
+			       bch_btree_cache_params);
+
+	/* Cause future lookups for this node to fail: */
+	bkey_i_to_extent(&b->key)->v._data[0] = 0;
+}
+
+int mca_hash_insert(struct cache_set *c, struct btree *b,
+		    unsigned level, enum btree_id id)
+{
+	int ret;
+	b->level	= level;
+	b->btree_id	= id;
+
+	ret = rhashtable_lookup_insert_fast(&c->btree_cache_table, &b->hash,
+					    bch_btree_cache_params);
+	if (ret)
+		return ret;
+
+	mutex_lock(&c->btree_cache_lock);
+	list_add(&b->list, &c->btree_cache);
+	mutex_unlock(&c->btree_cache_lock);
+
+	return 0;
+}
+
+__flatten
+static inline struct btree *mca_find(struct cache_set *c,
+				     const struct bkey_i *k)
+{
+	return rhashtable_lookup_fast(&c->btree_cache_table, &PTR_HASH(k),
+				      bch_btree_cache_params);
+}
+
+/*
+ * this version is for btree nodes that have already been freed (we're not
+ * reaping a real btree node)
+ */
+static int mca_reap_notrace(struct cache_set *c, struct btree *b, bool flush)
+{
+	lockdep_assert_held(&c->btree_cache_lock);
+
+	if (!six_trylock_intent(&b->lock))
+		return -ENOMEM;
+
+	if (!six_trylock_write(&b->lock))
+		goto out_unlock_intent;
+
+	if (btree_node_write_error(b))
+		goto out_unlock;
+
+	if (!list_empty(&b->write_blocked))
+		goto out_unlock;
+
+	if (!flush &&
+	    (btree_node_dirty(b) ||
+	     btree_node_write_in_flight(b)))
+		goto out_unlock;
+
+	/*
+	 * Using the underscore version because we don't want to compact bsets
+	 * after the write, since this node is about to be evicted - unless
+	 * btree verify mode is enabled, since it runs out of the post write
+	 * cleanup:
+	 */
+	if (btree_node_dirty(b)) {
+		if (verify_btree_ondisk(c))
+			bch_btree_node_write(c, b, NULL, SIX_LOCK_intent, -1);
+		else
+			__bch_btree_node_write(c, b, NULL, SIX_LOCK_read, -1);
+	}
+
+	/* wait for any in flight btree write */
+	wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight,
+		       TASK_UNINTERRUPTIBLE);
+
+	return 0;
+out_unlock:
+	six_unlock_write(&b->lock);
+out_unlock_intent:
+	six_unlock_intent(&b->lock);
+	return -ENOMEM;
+}
+
+static int mca_reap(struct cache_set *c, struct btree *b, bool flush)
+{
+	int ret = mca_reap_notrace(c, b, flush);
+
+	trace_bcache_mca_reap(c, b, ret);
+	return ret;
+}
+
+static unsigned long bch_mca_scan(struct shrinker *shrink,
+				  struct shrink_control *sc)
+{
+	struct cache_set *c = container_of(shrink, struct cache_set,
+					   btree_cache_shrink);
+	struct btree *b, *t;
+	unsigned long nr = sc->nr_to_scan;
+	unsigned long can_free;
+	unsigned long touched = 0;
+	unsigned long freed = 0;
+	unsigned i;
+
+	u64 start_time = local_clock();
+
+	if (btree_shrinker_disabled(c))
+		return SHRINK_STOP;
+
+	if (c->btree_cache_alloc_lock)
+		return SHRINK_STOP;
+
+	/* Return -1 if we can't do anything right now */
+	if (sc->gfp_mask & __GFP_IO)
+		mutex_lock(&c->btree_cache_lock);
+	else if (!mutex_trylock(&c->btree_cache_lock))
+		return -1;
+
+	/*
+	 * It's _really_ critical that we don't free too many btree nodes - we
+	 * have to always leave ourselves a reserve. The reserve is how we
+	 * guarantee that allocating memory for a new btree node can always
+	 * succeed, so that inserting keys into the btree can always succeed and
+	 * IO can always make forward progress:
+	 */
+	nr /= btree_pages(c);
+	can_free = mca_can_free(c);
+	nr = min_t(unsigned long, nr, can_free);
+
+	i = 0;
+	list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
+		touched++;
+
+		if (freed >= nr)
+			break;
+
+		if (++i > 3 &&
+		    !mca_reap_notrace(c, b, false)) {
+			mca_data_free(c, b);
+			six_unlock_write(&b->lock);
+			six_unlock_intent(&b->lock);
+			freed++;
+		}
+	}
+restart:
+	list_for_each_entry_safe(b, t, &c->btree_cache, list) {
+		touched++;
+
+		if (freed >= nr) {
+			/* Save position */
+			if (&t->list != &c->btree_cache)
+				list_move_tail(&c->btree_cache, &t->list);
+			break;
+		}
+
+		if (!btree_node_accessed(b) &&
+		    !mca_reap(c, b, false)) {
+			/* can't call mca_hash_remove under btree_cache_lock  */
+			freed++;
+			if (&t->list != &c->btree_cache)
+				list_move_tail(&c->btree_cache, &t->list);
+
+			mca_data_free(c, b);
+			mutex_unlock(&c->btree_cache_lock);
+
+			mca_hash_remove(c, b);
+			six_unlock_write(&b->lock);
+			six_unlock_intent(&b->lock);
+
+			if (freed >= nr)
+				goto out;
+
+			if (sc->gfp_mask & __GFP_IO)
+				mutex_lock(&c->btree_cache_lock);
+			else if (!mutex_trylock(&c->btree_cache_lock))
+				goto out;
+			goto restart;
+		} else
+			clear_btree_node_accessed(b);
+	}
+
+	mutex_unlock(&c->btree_cache_lock);
+out:
+	bch_time_stats_update(&c->mca_scan_time, start_time);
+
+	trace_bcache_mca_scan(c,
+			      touched * btree_pages(c),
+			      freed * btree_pages(c),
+			      can_free * btree_pages(c),
+			      sc->nr_to_scan);
+
+	return (unsigned long) freed * btree_pages(c);
+}
+
+static unsigned long bch_mca_count(struct shrinker *shrink,
+				   struct shrink_control *sc)
+{
+	struct cache_set *c = container_of(shrink, struct cache_set,
+					   btree_cache_shrink);
+
+	if (btree_shrinker_disabled(c))
+		return 0;
+
+	if (c->btree_cache_alloc_lock)
+		return 0;
+
+	return mca_can_free(c) * btree_pages(c);
+}
+
+void bch_btree_cache_free(struct cache_set *c)
+{
+	struct btree *b;
+	unsigned i;
+
+	if (c->btree_cache_shrink.list.next)
+		unregister_shrinker(&c->btree_cache_shrink);
+
+	mutex_lock(&c->btree_cache_lock);
+
+#ifdef CONFIG_BCACHE_DEBUG
+	if (c->verify_data)
+		list_move(&c->verify_data->list, &c->btree_cache);
+
+	free_pages((unsigned long) c->verify_ondisk, ilog2(btree_pages(c)));
+#endif
+
+	for (i = 0; i < BTREE_ID_NR; i++)
+		if (c->btree_roots[i].b)
+			list_add(&c->btree_roots[i].b->list, &c->btree_cache);
+
+	list_splice(&c->btree_cache_freeable,
+		    &c->btree_cache);
+
+	while (!list_empty(&c->btree_cache)) {
+		b = list_first_entry(&c->btree_cache, struct btree, list);
+
+		if (btree_node_dirty(b))
+			bch_btree_complete_write(c, b, btree_current_write(b));
+		clear_btree_node_dirty(b);
+
+		mca_data_free(c, b);
+	}
+
+	while (!list_empty(&c->btree_cache_freed)) {
+		b = list_first_entry(&c->btree_cache_freed,
+				     struct btree, list);
+		list_del(&b->list);
+		kfree(b);
+	}
+
+	mutex_unlock(&c->btree_cache_lock);
+
+	if (c->btree_cache_table_init_done)
+		rhashtable_destroy(&c->btree_cache_table);
+}
+
+int bch_btree_cache_alloc(struct cache_set *c)
+{
+	unsigned i;
+	int ret;
+
+	ret = rhashtable_init(&c->btree_cache_table, &bch_btree_cache_params);
+	if (ret)
+		return ret;
+
+	c->btree_cache_table_init_done = true;
+
+	bch_recalc_btree_reserve(c);
+
+	for (i = 0; i < c->btree_cache_reserve; i++)
+		if (!mca_bucket_alloc(c, GFP_KERNEL))
+			return -ENOMEM;
+
+	list_splice_init(&c->btree_cache,
+			 &c->btree_cache_freeable);
+
+#ifdef CONFIG_BCACHE_DEBUG
+	mutex_init(&c->verify_lock);
+
+	c->verify_ondisk = (void *)
+		__get_free_pages(GFP_KERNEL, ilog2(btree_pages(c)));
+	if (!c->verify_ondisk)
+		return -ENOMEM;
+
+	c->verify_data = mca_bucket_alloc(c, GFP_KERNEL);
+	if (!c->verify_data)
+		return -ENOMEM;
+
+	list_del_init(&c->verify_data->list);
+#endif
+
+	c->btree_cache_shrink.count_objects = bch_mca_count;
+	c->btree_cache_shrink.scan_objects = bch_mca_scan;
+	c->btree_cache_shrink.seeks = 4;
+	c->btree_cache_shrink.batch = btree_pages(c) * 2;
+	register_shrinker(&c->btree_cache_shrink);
+
+	return 0;
+}
+
+/*
+ * We can only have one thread cannibalizing other cached btree nodes at a time,
+ * or we'll deadlock. We use an open coded mutex to ensure that, which a
+ * cannibalize_bucket() will take. This means every time we unlock the root of
+ * the btree, we need to release this lock if we have it held.
+ */
+void mca_cannibalize_unlock(struct cache_set *c)
+{
+	if (c->btree_cache_alloc_lock == current) {
+		trace_bcache_mca_cannibalize_unlock(c);
+		c->btree_cache_alloc_lock = NULL;
+		closure_wake_up(&c->mca_wait);
+	}
+}
+
+int mca_cannibalize_lock(struct cache_set *c, struct closure *cl)
+{
+	struct task_struct *old;
+
+	old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current);
+	if (old == NULL || old == current)
+		goto success;
+
+	if (!cl) {
+		trace_bcache_mca_cannibalize_lock_fail(c);
+		return -ENOMEM;
+	}
+
+	closure_wait(&c->mca_wait, cl);
+
+	/* Try again, after adding ourselves to waitlist */
+	old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current);
+	if (old == NULL || old == current) {
+		/* We raced */
+		closure_wake_up(&c->mca_wait);
+		goto success;
+	}
+
+	trace_bcache_mca_cannibalize_lock_fail(c);
+	return -EAGAIN;
+
+success:
+	trace_bcache_mca_cannibalize_lock(c);
+	return 0;
+}
+
+static struct btree *mca_cannibalize(struct cache_set *c)
+{
+	struct btree *b;
+
+	list_for_each_entry_reverse(b, &c->btree_cache, list)
+		if (!mca_reap(c, b, false))
+			return b;
+
+	while (1) {
+		list_for_each_entry_reverse(b, &c->btree_cache, list)
+			if (!mca_reap(c, b, true))
+				return b;
+
+		/*
+		 * Rare case: all nodes were intent-locked.
+		 * Just busy-wait.
+		 */
+		WARN_ONCE(1, "btree cache cannibalize failed\n");
+		cond_resched();
+	}
+}
+
+struct btree *mca_alloc(struct cache_set *c)
+{
+	struct btree *b;
+	u64 start_time = local_clock();
+
+	mutex_lock(&c->btree_cache_lock);
+
+	/*
+	 * btree_free() doesn't free memory; it sticks the node on the end of
+	 * the list. Check if there's any freed nodes there:
+	 */
+	list_for_each_entry(b, &c->btree_cache_freeable, list)
+		if (!mca_reap_notrace(c, b, false))
+			goto out_unlock;
+
+	/*
+	 * We never free struct btree itself, just the memory that holds the on
+	 * disk node. Check the freed list before allocating a new one:
+	 */
+	list_for_each_entry(b, &c->btree_cache_freed, list)
+		if (!mca_reap_notrace(c, b, false)) {
+			mca_data_alloc(c, b, __GFP_NOWARN|GFP_NOIO);
+			if (b->data)
+				goto out_unlock;
+
+			six_unlock_write(&b->lock);
+			six_unlock_intent(&b->lock);
+			goto err;
+		}
+
+	b = mca_bucket_alloc(c, __GFP_NOWARN|GFP_NOIO);
+	if (!b)
+		goto err;
+
+	BUG_ON(!six_trylock_intent(&b->lock));
+	BUG_ON(!six_trylock_write(&b->lock));
+out_unlock:
+	BUG_ON(bkey_extent_is_data(&b->key.k) && PTR_HASH(&b->key));
+	BUG_ON(btree_node_write_in_flight(b));
+
+	list_del_init(&b->list);
+	mutex_unlock(&c->btree_cache_lock);
+out:
+	b->flags		= 0;
+	b->written		= 0;
+	b->nsets		= 0;
+	b->sib_u64s[0]		= 0;
+	b->sib_u64s[1]		= 0;
+	b->whiteout_u64s	= 0;
+	b->uncompacted_whiteout_u64s = 0;
+	bch_btree_keys_init(b, &c->expensive_debug_checks);
+
+	bch_time_stats_update(&c->mca_alloc_time, start_time);
+
+	return b;
+err:
+	/* Try to cannibalize another cached btree node: */
+	if (c->btree_cache_alloc_lock == current) {
+		b = mca_cannibalize(c);
+		list_del_init(&b->list);
+		mutex_unlock(&c->btree_cache_lock);
+
+		mca_hash_remove(c, b);
+
+		trace_bcache_mca_cannibalize(c);
+		goto out;
+	}
+
+	mutex_unlock(&c->btree_cache_lock);
+	return ERR_PTR(-ENOMEM);
+}
+
+/* Slowpath, don't want it inlined into btree_iter_traverse() */
+static noinline struct btree *bch_btree_node_fill(struct btree_iter *iter,
+						  const struct bkey_i *k,
+						  unsigned level,
+						  enum six_lock_type lock_type)
+{
+	struct cache_set *c = iter->c;
+	struct btree *b;
+
+	b = mca_alloc(c);
+	if (IS_ERR(b))
+		return b;
+
+	bkey_copy(&b->key, k);
+	if (mca_hash_insert(c, b, level, iter->btree_id)) {
+		/* raced with another fill: */
+
+		/* mark as unhashed... */
+		bkey_i_to_extent(&b->key)->v._data[0] = 0;
+
+		mutex_lock(&c->btree_cache_lock);
+		list_add(&b->list, &c->btree_cache_freeable);
+		mutex_unlock(&c->btree_cache_lock);
+
+		six_unlock_write(&b->lock);
+		six_unlock_intent(&b->lock);
+		return NULL;
+	}
+
+	/*
+	 * If the btree node wasn't cached, we can't drop our lock on
+	 * the parent until after it's added to the cache - because
+	 * otherwise we could race with a btree_split() freeing the node
+	 * we're trying to lock.
+	 *
+	 * But the deadlock described below doesn't exist in this case,
+	 * so it's safe to not drop the parent lock until here:
+	 */
+	if (btree_node_read_locked(iter, level + 1))
+		btree_node_unlock(iter, level + 1);
+
+	bch_btree_node_read(c, b);
+	six_unlock_write(&b->lock);
+
+	if (lock_type == SIX_LOCK_read)
+		six_lock_downgrade(&b->lock);
+
+	return b;
+}
+
+/**
+ * bch_btree_node_get - find a btree node in the cache and lock it, reading it
+ * in from disk if necessary.
+ *
+ * If IO is necessary and running under generic_make_request, returns -EAGAIN.
+ *
+ * The btree node will have either a read or a write lock held, depending on
+ * the @write parameter.
+ */
+struct btree *bch_btree_node_get(struct btree_iter *iter,
+				 const struct bkey_i *k, unsigned level,
+				 enum six_lock_type lock_type)
+{
+	struct btree *b;
+	struct bset_tree *t;
+
+	BUG_ON(level >= BTREE_MAX_DEPTH);
+retry:
+	rcu_read_lock();
+	b = mca_find(iter->c, k);
+	rcu_read_unlock();
+
+	if (unlikely(!b)) {
+		/*
+		 * We must have the parent locked to call bch_btree_node_fill(),
+		 * else we could read in a btree node from disk that's been
+		 * freed:
+		 */
+		b = bch_btree_node_fill(iter, k, level, lock_type);
+
+		/* We raced and found the btree node in the cache */
+		if (!b)
+			goto retry;
+
+		if (IS_ERR(b))
+			return b;
+	} else {
+		/*
+		 * There's a potential deadlock with splits and insertions into
+		 * interior nodes we have to avoid:
+		 *
+		 * The other thread might be holding an intent lock on the node
+		 * we want, and they want to update its parent node so they're
+		 * going to upgrade their intent lock on the parent node to a
+		 * write lock.
+		 *
+		 * But if we're holding a read lock on the parent, and we're
+		 * trying to get the intent lock they're holding, we deadlock.
+		 *
+		 * So to avoid this we drop the read locks on parent nodes when
+		 * we're starting to take intent locks - and handle the race.
+		 *
+		 * The race is that they might be about to free the node we
+		 * want, and dropping our read lock on the parent node lets them
+		 * update the parent marking the node we want as freed, and then
+		 * free it:
+		 *
+		 * To guard against this, btree nodes are evicted from the cache
+		 * when they're freed - and PTR_HASH() is zeroed out, which we
+		 * check for after we lock the node.
+		 *
+		 * Then, btree_node_relock() on the parent will fail - because
+		 * the parent was modified, when the pointer to the node we want
+		 * was removed - and we'll bail out:
+		 */
+		if (btree_node_read_locked(iter, level + 1))
+			btree_node_unlock(iter, level + 1);
+
+		if (!btree_node_lock(b, k->k.p, level, iter, lock_type))
+			return ERR_PTR(-EINTR);
+
+		if (unlikely(PTR_HASH(&b->key) != PTR_HASH(k) ||
+			     b->level != level ||
+			     race_fault())) {
+			six_unlock_type(&b->lock, lock_type);
+			if (btree_node_relock(iter, level + 1))
+				goto retry;
+
+			return ERR_PTR(-EINTR);
+		}
+	}
+
+	prefetch(b->aux_data);
+
+	for_each_bset(b, t) {
+		void *p = (u64 *) b->aux_data + t->aux_data_offset;
+
+		prefetch(p + L1_CACHE_BYTES * 0);
+		prefetch(p + L1_CACHE_BYTES * 1);
+		prefetch(p + L1_CACHE_BYTES * 2);
+	}
+
+	/* avoid atomic set bit if it's not needed: */
+	if (btree_node_accessed(b))
+		set_btree_node_accessed(b);
+
+	if (unlikely(btree_node_read_error(b))) {
+		six_unlock_type(&b->lock, lock_type);
+		return ERR_PTR(-EIO);
+	}
+
+	EBUG_ON(!b->written);
+	EBUG_ON(b->btree_id != iter->btree_id ||
+		BSET_BTREE_LEVEL(&b->data->keys) != level ||
+		bkey_cmp(b->data->max_key, k->k.p));
+
+	return b;
+}