Update bcachefs sources to 9e7ae5219c bcachefs: Make write points more dynamic

26 files changed, 766 insertions, 568 deletions

diff --git a/libbcachefs/alloc.c b/libbcachefs/alloc.c
index a1086576..dc7348fc 100644
--- a/libbcachefs/alloc.c
+++ b/libbcachefs/alloc.c
@@ -70,6 +70,7 @@
 #include <linux/kthread.h>
 #include <linux/math64.h>
 #include <linux/random.h>
+#include <linux/rculist.h>
 #include <linux/rcupdate.h>
 #include <linux/sched/task.h>
 #include <linux/sort.h>
@@ -1118,6 +1119,7 @@ static enum bucket_alloc_ret __bch2_bucket_alloc_set(struct bch_fs *c,
 {
 	enum bucket_alloc_ret ret = NO_DEVICES;
 	struct dev_alloc_list devs_sorted;
+	u64 buckets_free;
 	unsigned i;
 
 	BUG_ON(nr_replicas > ARRAY_SIZE(ob->ptrs));
@@ -1127,46 +1129,55 @@ static enum bucket_alloc_ret __bch2_bucket_alloc_set(struct bch_fs *c,
 
 	rcu_read_lock();
 	devs_sorted = bch2_wp_alloc_list(c, wp, devs);
+	spin_lock(&ob->lock);
 
 	for (i = 0; i < devs_sorted.nr; i++) {
 		struct bch_dev *ca =
 			rcu_dereference(c->devs[devs_sorted.devs[i]]);
-		long bucket;
+		struct open_bucket_ptr ptr;
 
 		if (!ca)
 			continue;
 
-		bucket = bch2_bucket_alloc(c, ca, reserve);
-		if (bucket < 0) {
-			ret = FREELIST_EMPTY;
-			continue;
-		}
-
-		wp->next_alloc[ca->dev_idx] +=
-			div64_u64(U64_MAX, dev_buckets_free(ca) *
-				  ca->mi.bucket_size);
-		bch2_wp_rescale(c, ca, wp);
+		if (wp->type == BCH_DATA_USER &&
+		    ca->open_buckets_partial_nr) {
+			ptr = ca->open_buckets_partial[--ca->open_buckets_partial_nr];
+		} else {
+			long bucket = bch2_bucket_alloc(c, ca, reserve);
+			if (bucket < 0) {
+				ret = FREELIST_EMPTY;
+				continue;
+			}
 
-		__clear_bit(ca->dev_idx, devs->d);
+			ptr = (struct open_bucket_ptr) {
+				.ptr.gen	= ca->buckets[bucket].mark.gen,
+				.ptr.offset	= bucket_to_sector(ca, bucket),
+				.ptr.dev	= ca->dev_idx,
+				.sectors_free	= ca->mi.bucket_size,
+			};
+		}
 
 		/*
 		 * open_bucket_add_buckets expects new pointers at the head of
 		 * the list:
 		 */
-		BUG_ON(ob->nr_ptrs >= BCH_REPLICAS_MAX);
+		BUG_ON(ob->nr_ptrs >= ARRAY_SIZE(ob->ptrs));
 		memmove(&ob->ptrs[1],
 			&ob->ptrs[0],
 			ob->nr_ptrs * sizeof(ob->ptrs[0]));
-		memmove(&ob->ptr_offset[1],
-			&ob->ptr_offset[0],
-			ob->nr_ptrs * sizeof(ob->ptr_offset[0]));
 		ob->nr_ptrs++;
-		ob->ptrs[0] = (struct bch_extent_ptr) {
-			.gen	= ca->buckets[bucket].mark.gen,
-			.offset	= bucket_to_sector(ca, bucket),
-			.dev	= ca->dev_idx,
-		};
-		ob->ptr_offset[0] = 0;
+		ob->ptrs[0] = ptr;
+
+		buckets_free = U64_MAX, dev_buckets_free(ca);
+		if (buckets_free)
+			wp->next_alloc[ca->dev_idx] +=
+				div64_u64(U64_MAX, buckets_free *
+					  ca->mi.bucket_size);
+		else
+			wp->next_alloc[ca->dev_idx] = U64_MAX;
+		bch2_wp_rescale(c, ca, wp);
+
+		__clear_bit(ca->dev_idx, devs->d);
 
 		if (ob->nr_ptrs == nr_replicas) {
 			ret = ALLOC_SUCCESS;
@@ -1175,6 +1186,7 @@ static enum bucket_alloc_ret __bch2_bucket_alloc_set(struct bch_fs *c,
 	}
 
 	EBUG_ON(ret != ALLOC_SUCCESS && reserve == RESERVE_MOVINGGC);
+	spin_unlock(&ob->lock);
 	rcu_read_unlock();
 	return ret;
 }
@@ -1242,24 +1254,45 @@ static int bch2_bucket_alloc_set(struct bch_fs *c, struct write_point *wp,
 
 void bch2_open_bucket_put(struct bch_fs *c, struct open_bucket *ob)
 {
-	const struct bch_extent_ptr *ptr;
+	const struct open_bucket_ptr *ptr;
 	u8 new_ob;
 
 	if (!atomic_dec_and_test(&ob->pin))
 		return;
 
-	spin_lock(&c->open_buckets_lock);
+	down_read(&c->alloc_gc_lock);
+	spin_lock(&ob->lock);
+
 	open_bucket_for_each_ptr(ob, ptr) {
-		struct bch_dev *ca = c->devs[ptr->dev];
+		struct bch_dev *ca = c->devs[ptr->ptr.dev];
 
-		bch2_mark_alloc_bucket(ca, PTR_BUCKET(ca, ptr), false);
+		if (ptr->sectors_free) {
+			/*
+			 * This is a ptr to a bucket that still has free space,
+			 * but we don't want to use it
+			 */
+			BUG_ON(ca->open_buckets_partial_nr >=
+			       ARRAY_SIZE(ca->open_buckets_partial));
+
+			spin_lock(&ca->freelist_lock);
+			ca->open_buckets_partial[ca->open_buckets_partial_nr++]
+				= *ptr;
+			spin_unlock(&ca->freelist_lock);
+		} else {
+			bch2_mark_alloc_bucket(ca, PTR_BUCKET(ca, &ptr->ptr), false);
+		}
 	}
-
 	ob->nr_ptrs = 0;
+
+	spin_unlock(&ob->lock);
+	up_read(&c->alloc_gc_lock);
+
 	new_ob = ob->new_ob;
 	ob->new_ob = 0;
 
-	list_move(&ob->list, &c->open_buckets_free);
+	spin_lock(&c->open_buckets_lock);
+	ob->freelist = c->open_buckets_freelist;
+	c->open_buckets_freelist = ob - c->open_buckets;
 	c->open_buckets_nr_free++;
 	spin_unlock(&c->open_buckets_lock);
 
@@ -1270,22 +1303,19 @@ void bch2_open_bucket_put(struct bch_fs *c, struct open_bucket *ob)
 }
 
 static struct open_bucket *bch2_open_bucket_get(struct bch_fs *c,
-					       unsigned nr_reserved,
-					       struct closure *cl)
+						unsigned nr_reserved,
+						struct closure *cl)
 {
 	struct open_bucket *ret;
 
 	spin_lock(&c->open_buckets_lock);
 
 	if (c->open_buckets_nr_free > nr_reserved) {
-		BUG_ON(list_empty(&c->open_buckets_free));
-		ret = list_first_entry(&c->open_buckets_free,
-				       struct open_bucket, list);
-		list_move(&ret->list, &c->open_buckets_open);
-		BUG_ON(ret->nr_ptrs);
+		BUG_ON(!c->open_buckets_freelist);
 
+		ret = c->open_buckets + c->open_buckets_freelist;
+		c->open_buckets_freelist = ret->freelist;
 		atomic_set(&ret->pin, 1); /* XXX */
-		ret->has_full_ptrs	= false;
 
 		BUG_ON(ret->new_ob);
 		BUG_ON(ret->nr_ptrs);
@@ -1307,148 +1337,259 @@ static struct open_bucket *bch2_open_bucket_get(struct bch_fs *c,
 	return ret;
 }
 
-static unsigned ob_ptr_sectors_free(struct bch_fs *c,
-				    struct open_bucket *ob,
-				    struct bch_extent_ptr *ptr)
-{
-	struct bch_dev *ca = c->devs[ptr->dev];
-	unsigned i = ptr - ob->ptrs;
-	unsigned used = bucket_remainder(ca, ptr->offset) +
-		ob->ptr_offset[i];
-
-	BUG_ON(used > ca->mi.bucket_size);
-
-	return ca->mi.bucket_size - used;
-}
-
 static unsigned open_bucket_sectors_free(struct bch_fs *c,
 					 struct open_bucket *ob,
 					 unsigned nr_replicas)
 {
-	unsigned i, sectors_free = UINT_MAX;
+	unsigned sectors_free = UINT_MAX;
+	struct open_bucket_ptr *ptr;
 
-	for (i = 0; i < min(nr_replicas, ob->nr_ptrs); i++)
-		sectors_free = min(sectors_free,
-				   ob_ptr_sectors_free(c, ob, &ob->ptrs[i]));
+	open_bucket_for_each_ptr(ob, ptr)
+		sectors_free = min(sectors_free, ptr->sectors_free);
 
 	return sectors_free != UINT_MAX ? sectors_free : 0;
 }
 
-static void open_bucket_copy_unused_ptrs(struct bch_fs *c,
-					 struct open_bucket *new,
-					 struct open_bucket *old)
+static void open_bucket_move_ptrs(struct bch_fs *c,
+				  struct open_bucket *dst,
+				  struct open_bucket *src,
+				  struct bch_devs_mask *devs,
+				  unsigned nr_ptrs_dislike)
 {
 	bool moved_ptr = false;
 	int i;
 
-	for (i = old->nr_ptrs - 1; i >= 0; --i)
-		if (ob_ptr_sectors_free(c, old, &old->ptrs[i])) {
-			BUG_ON(new->nr_ptrs >= BCH_REPLICAS_MAX);
+	down_read(&c->alloc_gc_lock);
 
-			new->ptrs[new->nr_ptrs]		= old->ptrs[i];
-			new->ptr_offset[new->nr_ptrs]	= old->ptr_offset[i];
-			new->nr_ptrs++;
+	if (dst < src) {
+		spin_lock(&dst->lock);
+		spin_lock_nested(&src->lock, 1);
+	} else {
+		spin_lock(&src->lock);
+		spin_lock_nested(&dst->lock, 1);
+	}
 
-			old->nr_ptrs--;
-			memmove(&old->ptrs[i],
-				&old->ptrs[i + 1],
-				(old->nr_ptrs - i) * sizeof(old->ptrs[0]));
-			memmove(&old->ptr_offset[i],
-				&old->ptr_offset[i + 1],
-				(old->nr_ptrs - i) * sizeof(old->ptr_offset[0]));
+	for (i = src->nr_ptrs - 1; i >= 0; --i) {
+		if (!src->ptrs[i].sectors_free) {
+			/*
+			 * Don't do anything: leave the ptr on the old
+			 * open_bucket for gc to find
+			 */
+		} else if (nr_ptrs_dislike &&
+			   !test_bit(src->ptrs[i].ptr.dev, devs->d)) {
+			/*
+			 * We don't want this pointer; bch2_open_bucket_put()
+			 * will stick it on ca->open_buckets_partial to be
+			 * reused
+			 */
+			--nr_ptrs_dislike;
+		} else {
+			BUG_ON(dst->nr_ptrs >= ARRAY_SIZE(dst->ptrs));
+
+			dst->ptrs[dst->nr_ptrs++] = src->ptrs[i];
+
+			src->nr_ptrs--;
+			memmove(&src->ptrs[i],
+				&src->ptrs[i + 1],
+				(src->nr_ptrs - i) * sizeof(src->ptrs[0]));
 
 			moved_ptr = true;
 		}
+	}
 
 	if (moved_ptr) {
-		BUG_ON(old->new_ob);
+		BUG_ON(src->new_ob);
 
-		atomic_inc(&new->pin);
-		old->new_ob = new - c->open_buckets;
+		atomic_inc(&dst->pin);
+		src->new_ob = dst - c->open_buckets;
 	}
+
+	spin_unlock(&dst->lock);
+	spin_unlock(&src->lock);
+	up_read(&c->alloc_gc_lock);
 }
 
 static void verify_not_stale(struct bch_fs *c, const struct open_bucket *ob)
 {
 #ifdef CONFIG_BCACHEFS_DEBUG
-	const struct bch_extent_ptr *ptr;
+	const struct open_bucket_ptr *ptr;
 
 	open_bucket_for_each_ptr(ob, ptr) {
-		struct bch_dev *ca = c->devs[ptr->dev];
+		struct bch_dev *ca = c->devs[ptr->ptr.dev];
 
-		BUG_ON(ptr_stale(ca, ptr));
+		BUG_ON(ptr_stale(ca, &ptr->ptr));
 	}
 #endif
 }
 
 /* Sector allocator */
 
-static struct open_bucket *lock_writepoint(struct bch_fs *c,
-					   struct write_point *wp)
-{
-	struct open_bucket *ob;
-
-	while ((ob = ACCESS_ONCE(wp->b))) {
-		mutex_lock(&ob->lock);
-		if (wp->b == ob)
-			break;
-
-		mutex_unlock(&ob->lock);
-	}
-
-	return ob;
-}
-
 static int open_bucket_add_buckets(struct bch_fs *c,
 				   struct write_point *wp,
+				   struct bch_devs_mask *_devs,
 				   struct open_bucket *ob,
 				   unsigned nr_replicas,
-				   unsigned nr_replicas_required,
 				   enum alloc_reserve reserve,
 				   struct closure *cl)
 {
 	struct bch_devs_mask devs = c->rw_devs[wp->type];
-	unsigned i;
-	int ret;
+	struct open_bucket_ptr *ptr;
 
 	if (ob->nr_ptrs >= nr_replicas)
 		return 0;
 
+	if (_devs)
+		bitmap_and(devs.d, devs.d, _devs->d, BCH_SB_MEMBERS_MAX);
+
 	/* Don't allocate from devices we already have pointers to: */
-	for (i = 0; i < ob->nr_ptrs; i++)
-		__clear_bit(ob->ptrs[i].dev, devs.d);
+	open_bucket_for_each_ptr(ob, ptr)
+		if (ptr->sectors_free)
+			__clear_bit(ptr->ptr.dev, devs.d);
 
-	if (wp->group)
-		bitmap_and(devs.d, devs.d, wp->group->d, BCH_SB_MEMBERS_MAX);
+	return bch2_bucket_alloc_set(c, wp, ob, nr_replicas,
+				     reserve, &devs, cl);
+}
 
-	ret = bch2_bucket_alloc_set(c, wp, ob, nr_replicas,
-				    reserve, &devs, cl);
+static struct write_point *__writepoint_find(struct hlist_head *head,
+					     unsigned long write_point)
+{
+	struct write_point *wp;
 
-	if (ret == -EROFS &&
-	    ob->nr_ptrs >= nr_replicas_required)
-		ret = 0;
+	hlist_for_each_entry_rcu(wp, head, node) {
+		if (wp->write_point == write_point)
+			continue;
 
-	return ret;
+		mutex_lock(&wp->lock);
+		if (wp->write_point == write_point)
+			return wp;
+		mutex_unlock(&wp->lock);
+	}
+
+	return NULL;
+}
+
+static struct hlist_head *writepoint_hash(struct bch_fs *c,
+					  unsigned long write_point)
+{
+	unsigned hash =
+		hash_long(write_point, ilog2(ARRAY_SIZE(c->write_points_hash)));
+
+	return &c->write_points_hash[hash];
+}
+
+static struct write_point *writepoint_find(struct bch_fs *c,
+					   enum bch_data_type data_type,
+					   unsigned long write_point)
+{
+	struct write_point *wp, *oldest = NULL;
+	struct hlist_head *head;
+
+	switch (data_type) {
+	case BCH_DATA_BTREE:
+		wp = &c->btree_write_point;
+		mutex_lock(&wp->lock);
+		return wp;
+	case BCH_DATA_USER:
+		break;
+	default:
+		BUG();
+	}
+
+	head = writepoint_hash(c, write_point);
+	wp = __writepoint_find(head, write_point);
+	if (wp)
+		goto out;
+
+	mutex_lock(&c->write_points_hash_lock);
+	wp = __writepoint_find(head, write_point);
+	if (wp)
+		goto out_unlock;
+
+	for (wp = c->write_points;
+	     wp < c->write_points + ARRAY_SIZE(c->write_points);
+	     wp++)
+		if (!oldest || time_before64(wp->last_used, oldest->last_used))
+			oldest = wp;
+
+	wp = oldest;
+	BUG_ON(!wp);
+
+	mutex_lock(&wp->lock);
+	hlist_del_rcu(&wp->node);
+	wp->write_point = write_point;
+	hlist_add_head_rcu(&wp->node, head);
+out_unlock:
+	mutex_unlock(&c->write_points_hash_lock);
+out:
+	wp->last_used = sched_clock();
+	return wp;
 }
 
 /*
  * Get us an open_bucket we can allocate from, return with it locked:
  */
-struct open_bucket *bch2_alloc_sectors_start(struct bch_fs *c,
-					     struct write_point *wp,
+struct write_point *bch2_alloc_sectors_start(struct bch_fs *c,
+					     enum bch_data_type data_type,
+					     struct bch_devs_mask *devs,
+					     unsigned long write_point,
 					     unsigned nr_replicas,
 					     unsigned nr_replicas_required,
 					     enum alloc_reserve reserve,
+					     unsigned flags,
 					     struct closure *cl)
 {
 	struct open_bucket *ob;
-	unsigned open_buckets_reserved = wp == &c->btree_write_point
+	struct write_point *wp;
+	struct open_bucket_ptr *ptr;
+	unsigned open_buckets_reserved = data_type == BCH_DATA_BTREE
 		? 0 : BTREE_NODE_RESERVE;
+	unsigned nr_ptrs_empty = 0, nr_ptrs_dislike = 0;
 	int ret;
 
 	BUG_ON(!nr_replicas);
-retry:
-	ob = lock_writepoint(c, wp);
+
+	wp = writepoint_find(c, data_type, write_point);
+	BUG_ON(wp->type != data_type);
+
+	wp->last_used = sched_clock();
+
+	ob = wp->ob;
+
+	/* does ob have ptrs we don't need? */
+	open_bucket_for_each_ptr(ob, ptr) {
+		if (!ptr->sectors_free)
+			nr_ptrs_empty++;
+		else if (devs && !test_bit(ptr->ptr.dev, devs->d))
+			nr_ptrs_dislike++;
+	}
+
+	ret = open_bucket_add_buckets(c, wp, devs, ob,
+				nr_replicas + nr_ptrs_empty + nr_ptrs_dislike,
+				reserve, cl);
+	if (ret && ret != -EROFS)
+		goto err;
+
+	if (flags & BCH_WRITE_ONLY_SPECIFIED_DEVS)
+		goto alloc_done;
+
+	/*
+	 * XXX:
+	 * Should this allocation be _forced_ to used the specified device (e.g.
+	 * internal migration), or should we fall back to allocating from all
+	 * devices?
+	 */
+	ret = open_bucket_add_buckets(c, wp, NULL, ob,
+				nr_replicas + nr_ptrs_empty,
+				reserve, cl);
+	if (ret && ret != -EROFS)
+		goto err;
+alloc_done:
+	if (ob->nr_ptrs - nr_ptrs_empty -
+	    ((flags & BCH_WRITE_ONLY_SPECIFIED_DEVS) ? nr_ptrs_dislike : 0)
+	    < nr_replicas_required) {
+		ret = -EROFS;
+		goto err;
+	}
 
 	/*
 	 * If ob->sectors_free == 0, one or more of the buckets ob points to is
@@ -1456,53 +1597,34 @@ retry:
 	 * still needs to find them; instead, we must allocate a new open bucket
 	 * and copy any pointers to non-full buckets into the new open bucket.
 	 */
-	if (!ob || ob->has_full_ptrs) {
-		struct open_bucket *new_ob;
-
-		new_ob = bch2_open_bucket_get(c, open_buckets_reserved, cl);
-		if (IS_ERR(new_ob))
-			return new_ob;
-
-		mutex_lock(&new_ob->lock);
-
-		/*
-		 * We point the write point at the open_bucket before doing the
-		 * allocation to avoid a race with shutdown:
-		 */
-		if (race_fault() ||
-		    cmpxchg(&wp->b, ob, new_ob) != ob) {
-			/* We raced: */
-			mutex_unlock(&new_ob->lock);
-			bch2_open_bucket_put(c, new_ob);
-
-			if (ob)
-				mutex_unlock(&ob->lock);
-			goto retry;
+	BUG_ON(ob->nr_ptrs - nr_ptrs_empty - nr_replicas > nr_ptrs_dislike);
+	nr_ptrs_dislike = ob->nr_ptrs - nr_ptrs_empty - nr_replicas;
+
+	if (nr_ptrs_empty || nr_ptrs_dislike) {
+		ob = bch2_open_bucket_get(c, open_buckets_reserved, cl);
+		if (IS_ERR(ob)) {
+			ret = PTR_ERR(ob);
+			goto err;
 		}
 
-		if (ob) {
-			open_bucket_copy_unused_ptrs(c, new_ob, ob);
-			mutex_unlock(&ob->lock);
-			bch2_open_bucket_put(c, ob);
-		}
+		/* Remove pointers we don't want to use: */
 
-		ob = new_ob;
+		open_bucket_move_ptrs(c, ob, wp->ob, devs, nr_ptrs_dislike);
+		bch2_open_bucket_put(c, wp->ob);
+		wp->ob = ob;
 	}
 
-	ret = open_bucket_add_buckets(c, wp, ob, nr_replicas,
-				      nr_replicas_required,
-				      reserve, cl);
-	if (ret) {
-		mutex_unlock(&ob->lock);
-		return ERR_PTR(ret);
-	}
+	BUG_ON(ob->nr_ptrs < nr_replicas_required);
 
-	ob->sectors_free = open_bucket_sectors_free(c, ob, nr_replicas);
+	wp->sectors_free = open_bucket_sectors_free(c, ob, nr_replicas);
 
-	BUG_ON(!ob->sectors_free);
+	BUG_ON(!wp->sectors_free);
 	verify_not_stale(c, ob);
 
-	return ob;
+	return wp;
+err:
+	mutex_unlock(&wp->lock);
+	return ERR_PTR(ret);
 }
 
 /*
@@ -1514,29 +1636,26 @@ void bch2_alloc_sectors_append_ptrs(struct bch_fs *c, struct bkey_i_extent *e,
 				    unsigned sectors)
 {
 	struct bch_extent_ptr tmp;
-	bool has_data = false;
-	unsigned i;
+	struct open_bucket_ptr *ptr;
 
 	/*
 	 * We're keeping any existing pointer k has, and appending new pointers:
 	 * __bch2_write() will only write to the pointers we add here:
 	 */
 
-	BUG_ON(sectors > ob->sectors_free);
-
-	/* didn't use all the ptrs: */
-	if (nr_replicas < ob->nr_ptrs)
-		has_data = true;
+	for (ptr = ob->ptrs;
+	     ptr < ob->ptrs + min_t(u8, ob->nr_ptrs, nr_replicas); ptr++) {
+		struct bch_dev *ca = c->devs[ptr->ptr.dev];
 
-	for (i = 0; i < min(ob->nr_ptrs, nr_replicas); i++) {
-		EBUG_ON(bch2_extent_has_device(extent_i_to_s_c(e), ob->ptrs[i].dev));
+		EBUG_ON(bch2_extent_has_device(extent_i_to_s_c(e), ptr->ptr.dev));
 
-		tmp = ob->ptrs[i];
+		tmp = ptr->ptr;
 		tmp.cached = bkey_extent_is_cached(&e->k);
-		tmp.offset += ob->ptr_offset[i];
+		tmp.offset += ca->mi.bucket_size - ptr->sectors_free;
 		extent_ptr_append(e, tmp);
 
-		ob->ptr_offset[i] += sectors;
+		BUG_ON(sectors > ptr->sectors_free);
+		ptr->sectors_free -= sectors;
 	}
 }
 
@@ -1544,25 +1663,27 @@ void bch2_alloc_sectors_append_ptrs(struct bch_fs *c, struct bkey_i_extent *e,
  * Append pointers to the space we just allocated to @k, and mark @sectors space
  * as allocated out of @ob
  */
-void bch2_alloc_sectors_done(struct bch_fs *c, struct write_point *wp,
-			    struct open_bucket *ob)
+void bch2_alloc_sectors_done(struct bch_fs *c, struct write_point *wp)
 {
-	bool has_data = false;
-	unsigned i;
+	struct open_bucket *ob = wp->ob, *new_ob = NULL;
+	struct open_bucket_ptr *ptr;
+	bool empty = false;
 
-	for (i = 0; i < ob->nr_ptrs; i++) {
-		if (!ob_ptr_sectors_free(c, ob, &ob->ptrs[i]))
-			ob->has_full_ptrs = true;
-		else
-			has_data = true;
-	}
+	open_bucket_for_each_ptr(ob, ptr)
+		empty |= !ptr->sectors_free;
+
+	if (empty)
+		new_ob = bch2_open_bucket_get(c, 0, NULL);
 
-	if (likely(has_data))
+	if (!IS_ERR_OR_NULL(new_ob)) {
+		/* writepoint's ref becomes our ref: */
+		wp->ob = new_ob;
+		open_bucket_move_ptrs(c, new_ob, ob, 0, 0);
+	} else {
 		atomic_inc(&ob->pin);
-	else
-		BUG_ON(xchg(&wp->b, NULL) != ob);
+	}
 
-	mutex_unlock(&ob->lock);
+	mutex_unlock(&wp->lock);
 }
 
 /*
@@ -1583,27 +1704,33 @@ void bch2_alloc_sectors_done(struct bch_fs *c, struct write_point *wp,
  * @cl - closure to wait for a bucket
  */
 struct open_bucket *bch2_alloc_sectors(struct bch_fs *c,
-				       struct write_point *wp,
+				       enum bch_data_type data_type,
+				       struct bch_devs_mask *devs,
+				       unsigned long write_point,
 				       struct bkey_i_extent *e,
 				       unsigned nr_replicas,
 				       unsigned nr_replicas_required,
 				       enum alloc_reserve reserve,
+				       unsigned flags,
 				       struct closure *cl)
 {
+	struct write_point *wp;
 	struct open_bucket *ob;
 
-	ob = bch2_alloc_sectors_start(c, wp, nr_replicas,
-				     nr_replicas_required,
-				     reserve, cl);
-	if (IS_ERR_OR_NULL(ob))
-		return ob;
+	wp = bch2_alloc_sectors_start(c, data_type, devs, write_point,
+				      nr_replicas, nr_replicas_required,
+				      reserve, flags, cl);
+	if (IS_ERR_OR_NULL(wp))
+		return ERR_CAST(wp);
 
-	if (e->k.size > ob->sectors_free)
-		bch2_key_resize(&e->k, ob->sectors_free);
+	ob = wp->ob;
+
+	if (e->k.size > wp->sectors_free)
+		bch2_key_resize(&e->k, wp->sectors_free);
 
 	bch2_alloc_sectors_append_ptrs(c, e, nr_replicas, ob, e->k.size);
 
-	bch2_alloc_sectors_done(c, wp, ob);
+	bch2_alloc_sectors_done(c, wp);
 
 	return ob;
 }
@@ -1640,8 +1767,7 @@ void bch2_recalc_capacity(struct bch_fs *c)
 	}
 
 	c->fastest_tier = fastest_tier != slowest_tier ? fastest_tier : NULL;
-
-	c->promote_write_point.group = &fastest_tier->devs;
+	c->fastest_devs = fastest_tier != slowest_tier ? &fastest_tier->devs : NULL;
 
 	if (!fastest_tier)
 		goto set_capacity;
@@ -1713,49 +1839,61 @@ set_capacity:
 	closure_wake_up(&c->freelist_wait);
 }
 
+static bool open_bucket_has_device(struct open_bucket *ob,
+				   struct bch_dev *ca)
+{
+	struct open_bucket_ptr *ptr;
+	bool ret = false;
+
+	spin_lock(&ob->lock);
+	open_bucket_for_each_ptr(ob, ptr)
+		ret |= ptr->ptr.dev == ca->dev_idx;
+	spin_unlock(&ob->lock);
+
+	return ret;
+}
+
 static void bch2_stop_write_point(struct bch_fs *c, struct bch_dev *ca,
 				  struct write_point *wp)
 {
 	struct open_bucket *ob;
-	struct bch_extent_ptr *ptr;
+	struct closure cl;
 
-	ob = lock_writepoint(c, wp);
-	if (!ob)
+	closure_init_stack(&cl);
+retry:
+	mutex_lock(&wp->lock);
+	if (!open_bucket_has_device(wp->ob, ca)) {
+		mutex_unlock(&wp->lock);
 		return;
+	}
 
-	for (ptr = ob->ptrs; ptr < ob->ptrs + ob->nr_ptrs; ptr++)
-		if (ptr->dev == ca->dev_idx)
-			goto found;
+	ob = bch2_open_bucket_get(c, 0, &cl);
+	if (IS_ERR(ob)) {
+		mutex_unlock(&wp->lock);
+		closure_sync(&cl);
+		goto retry;
+
+	}
 
-	mutex_unlock(&ob->lock);
-	return;
-found:
-	BUG_ON(xchg(&wp->b, NULL) != ob);
-	mutex_unlock(&ob->lock);
+	open_bucket_move_ptrs(c, ob, wp->ob, &ca->self, ob->nr_ptrs);
+	bch2_open_bucket_put(c, wp->ob);
+	wp->ob = ob;
 
-	/* Drop writepoint's ref: */
-	bch2_open_bucket_put(c, ob);
+	mutex_unlock(&wp->lock);
 }
 
 static bool bch2_dev_has_open_write_point(struct bch_fs *c, struct bch_dev *ca)
 {
-	struct bch_extent_ptr *ptr;
 	struct open_bucket *ob;
+	bool ret = false;
 
 	for (ob = c->open_buckets;
 	     ob < c->open_buckets + ARRAY_SIZE(c->open_buckets);
 	     ob++)
-		if (atomic_read(&ob->pin)) {
-			mutex_lock(&ob->lock);
-			for (ptr = ob->ptrs; ptr < ob->ptrs + ob->nr_ptrs; ptr++)
-				if (ptr->dev == ca->dev_idx) {
-					mutex_unlock(&ob->lock);
-					return true;
-				}
-			mutex_unlock(&ob->lock);
-		}
+		if (atomic_read(&ob->pin))
+			ret |= open_bucket_has_device(ob, ca);
 
-	return false;
+	return ret;
 }
 
 /* device goes ro: */
@@ -1782,11 +1920,6 @@ void bch2_dev_allocator_remove(struct bch_fs *c, struct bch_dev *ca)
 	/* Next, close write points that point to this device... */
 	for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
 		bch2_stop_write_point(c, ca, &c->write_points[i]);
-
-	bch2_stop_write_point(c, ca, &ca->copygc_write_point);
-	bch2_stop_write_point(c, ca, &c->promote_write_point);
-	bch2_stop_write_point(c, ca, &c->tiers[ca->mi.tier].wp);
-	bch2_stop_write_point(c, ca, &c->migration_write_point);
 	bch2_stop_write_point(c, ca, &c->btree_write_point);
 
 	mutex_lock(&c->btree_reserve_cache_lock);
@@ -1880,35 +2013,44 @@ int bch2_dev_allocator_start(struct bch_dev *ca)
 
 void bch2_fs_allocator_init(struct bch_fs *c)
 {
-	unsigned i;
+	struct open_bucket *ob;
+	struct write_point *wp;
 
-	INIT_LIST_HEAD(&c->open_buckets_open);
-	INIT_LIST_HEAD(&c->open_buckets_free);
+	mutex_init(&c->write_points_hash_lock);
+	init_rwsem(&c->alloc_gc_lock);
 	spin_lock_init(&c->open_buckets_lock);
 	bch2_prio_timer_init(c, READ);
 	bch2_prio_timer_init(c, WRITE);
 
 	/* open bucket 0 is a sentinal NULL: */
-	mutex_init(&c->open_buckets[0].lock);
-	INIT_LIST_HEAD(&c->open_buckets[0].list);
+	spin_lock_init(&c->open_buckets[0].lock);
 
-	for (i = 1; i < ARRAY_SIZE(c->open_buckets); i++) {
-		mutex_init(&c->open_buckets[i].lock);
+	for (ob = c->open_buckets + 1;
+	     ob < c->open_buckets + ARRAY_SIZE(c->open_buckets); ob++) {
+		spin_lock_init(&ob->lock);
 		c->open_buckets_nr_free++;
-		list_add(&c->open_buckets[i].list, &c->open_buckets_free);
+
+		ob->freelist = c->open_buckets_freelist;
+		c->open_buckets_freelist = ob - c->open_buckets;
 	}
 
-	c->journal.wp.type		= BCH_DATA_JOURNAL;
+	mutex_init(&c->btree_write_point.lock);
 	c->btree_write_point.type	= BCH_DATA_BTREE;
+	c->btree_write_point.ob		= bch2_open_bucket_get(c, 0, NULL);
+	BUG_ON(IS_ERR(c->btree_write_point.ob));
 
-	for (i = 0; i < ARRAY_SIZE(c->tiers); i++)
-		c->tiers[i].wp.type	= BCH_DATA_USER;
+	for (wp = c->write_points;
+	     wp < c->write_points + ARRAY_SIZE(c->write_points); wp++) {
+		mutex_init(&wp->lock);
+		wp->type	= BCH_DATA_USER;
+		wp->ob		= bch2_open_bucket_get(c, 0, NULL);
+		wp->last_used	= sched_clock();
 
-	for (i = 0; i < ARRAY_SIZE(c->write_points); i++)
-		c->write_points[i].type = BCH_DATA_USER;
+		wp->write_point	= (unsigned long) wp;
+		hlist_add_head_rcu(&wp->node, writepoint_hash(c, wp->write_point));
 
-	c->promote_write_point.type	= BCH_DATA_USER;
-	c->migration_write_point.type	= BCH_DATA_USER;
+		BUG_ON(IS_ERR(wp->ob));
+	}
 
 	c->pd_controllers_update_seconds = 5;
 	INIT_DELAYED_WORK(&c->pd_controllers_update, pd_controllers_update);
diff --git a/libbcachefs/alloc.h b/libbcachefs/alloc.h
index f07f1bfc..1ea747d2 100644
--- a/libbcachefs/alloc.h
+++ b/libbcachefs/alloc.h
@@ -28,20 +28,28 @@ long bch2_bucket_alloc(struct bch_fs *, struct bch_dev *, enum alloc_reserve);
 
 void bch2_open_bucket_put(struct bch_fs *, struct open_bucket *);
 
-struct open_bucket *bch2_alloc_sectors_start(struct bch_fs *,
-					    struct write_point *,
-					    unsigned, unsigned,
-					    enum alloc_reserve,
-					    struct closure *);
+struct write_point *bch2_alloc_sectors_start(struct bch_fs *,
+					     enum bch_data_type,
+					     struct bch_devs_mask *,
+					     unsigned long,
+					     unsigned, unsigned,
+					     enum alloc_reserve,
+					     unsigned,
+					     struct closure *);
 
 void bch2_alloc_sectors_append_ptrs(struct bch_fs *, struct bkey_i_extent *,
 				   unsigned, struct open_bucket *, unsigned);
-void bch2_alloc_sectors_done(struct bch_fs *, struct write_point *,
-			    struct open_bucket *);
-
-struct open_bucket *bch2_alloc_sectors(struct bch_fs *, struct write_point *,
-				      struct bkey_i_extent *, unsigned, unsigned,
-				      enum alloc_reserve, struct closure *);
+void bch2_alloc_sectors_done(struct bch_fs *, struct write_point *);
+
+struct open_bucket *bch2_alloc_sectors(struct bch_fs *,
+				       enum bch_data_type,
+				       struct bch_devs_mask *,
+				       unsigned long,
+				       struct bkey_i_extent *,
+				       unsigned, unsigned,
+				       enum alloc_reserve,
+				       unsigned,
+				       struct closure *);
 
 static inline void bch2_wake_allocator(struct bch_dev *ca)
 {
diff --git a/libbcachefs/alloc_types.h b/libbcachefs/alloc_types.h
index bee6d28d..c48d0aaa 100644
--- a/libbcachefs/alloc_types.h
+++ b/libbcachefs/alloc_types.h
@@ -2,6 +2,7 @@
 #define _BCACHEFS_ALLOC_TYPES_H
 
 #include <linux/mutex.h>
+#include <linux/spinlock.h>
 
 #include "clock_types.h"
 
@@ -44,39 +45,34 @@ enum alloc_reserve {
 
 /* Enough for 16 cache devices, 2 tiers and some left over for pipelining */
 #define OPEN_BUCKETS_COUNT	256
+#define WRITE_POINT_COUNT	32
 
-#define WRITE_POINT_COUNT	16
+struct open_bucket_ptr {
+	struct bch_extent_ptr	ptr;
+	unsigned		sectors_free;
+};
 
 struct open_bucket {
-	struct list_head	list;
-	struct mutex		lock;
+	spinlock_t		lock;
 	atomic_t		pin;
-	bool			has_full_ptrs;
+	u8			freelist;
 	u8			new_ob;
+	u8			nr_ptrs;
 
-	/*
-	 * recalculated every time we allocate from this open_bucket based on
-	 * how many pointers we're actually going to use:
-	 */
-	unsigned		sectors_free;
-	unsigned		nr_ptrs;
-	struct bch_extent_ptr	ptrs[BCH_REPLICAS_MAX];
-	unsigned		ptr_offset[BCH_REPLICAS_MAX];
+	struct open_bucket_ptr	ptrs[BCH_REPLICAS_MAX * 2];
 };
 
 struct write_point {
-	struct open_bucket	*b;
+	struct hlist_node	node;
+	struct mutex		lock;
+	u64			last_used;
+	unsigned long		write_point;
 	enum bch_data_type	type;
 
-	/*
-	 * If not NULL, cache group for tiering, promotion and moving GC -
-	 * always allocates a single replica
-	 *
-	 * Otherwise do a normal replicated bucket allocation that could come
-	 * from any device in tier 0 (foreground write)
-	 */
-	struct bch_devs_mask	*group;
+	/* calculated based on how many pointers we're actually going to use: */
+	unsigned		sectors_free;
 
+	struct open_bucket	*ob;
 	u64			next_alloc[BCH_SB_MEMBERS_MAX];
 };
 
diff --git a/libbcachefs/bcachefs.h b/libbcachefs/bcachefs.h
index 1828bfdf..58d4723e 100644
--- a/libbcachefs/bcachefs.h
+++ b/libbcachefs/bcachefs.h
@@ -392,6 +392,9 @@ struct bch_dev {
 	unsigned		nr_invalidated;
 	bool			alloc_thread_started;
 
+	struct open_bucket_ptr	open_buckets_partial[BCH_REPLICAS_MAX * WRITE_POINT_COUNT];
+	unsigned		open_buckets_partial_nr;
+
 	size_t			fifo_last_bucket;
 
 	/* Allocation stuff: */
@@ -426,8 +429,6 @@ struct bch_dev {
 
 	struct bch_pd_controller moving_gc_pd;
 
-	struct write_point	copygc_write_point;
-
 	struct journal_device	journal;
 
 	struct work_struct	io_error_work;
@@ -472,7 +473,6 @@ struct bch_tier {
 	struct bch_pd_controller pd;
 
 	struct bch_devs_mask	devs;
-	struct write_point	wp;
 };
 
 enum bch_fs_state {
@@ -546,40 +546,7 @@ struct bch_fs {
 	struct btree_root	btree_roots[BTREE_ID_NR];
 	struct mutex		btree_root_lock;
 
-	bool			btree_cache_table_init_done;
-	struct rhashtable	btree_cache_table;
-
-	/*
-	 * We never free a struct btree, except on shutdown - we just put it on
-	 * the btree_cache_freed list and reuse it later. This simplifies the
-	 * code, and it doesn't cost us much memory as the memory usage is
-	 * dominated by buffers that hold the actual btree node data and those
-	 * can be freed - and the number of struct btrees allocated is
-	 * effectively bounded.
-	 *
-	 * btree_cache_freeable effectively is a small cache - we use it because
-	 * high order page allocations can be rather expensive, and it's quite
-	 * common to delete and allocate btree nodes in quick succession. It
-	 * should never grow past ~2-3 nodes in practice.
-	 */
-	struct mutex		btree_cache_lock;
-	struct list_head	btree_cache;
-	struct list_head	btree_cache_freeable;
-	struct list_head	btree_cache_freed;
-
-	/* Number of elements in btree_cache + btree_cache_freeable lists */
-	unsigned		btree_cache_used;
-	unsigned		btree_cache_reserve;
-	struct shrinker		btree_cache_shrink;
-
-	/*
-	 * If we need to allocate memory for a new btree node and that
-	 * allocation fails, we can cannibalize another node in the btree cache
-	 * to satisfy the allocation - lock to guarantee only one thread does
-	 * this at a time:
-	 */
-	struct closure_waitlist	mca_wait;
-	struct task_struct	*btree_cache_alloc_lock;
+	struct btree_cache	btree_cache;
 
 	mempool_t		btree_reserve_pool;
 
@@ -606,6 +573,7 @@ struct bch_fs {
 	struct workqueue_struct	*copygc_wq;
 
 	/* ALLOCATION */
+	struct rw_semaphore	alloc_gc_lock;
 	struct bch_pd_controller foreground_write_pd;
 	struct delayed_work	pd_controllers_update;
 	unsigned		pd_controllers_update_seconds;
@@ -622,6 +590,7 @@ struct bch_fs {
 	struct bch_devs_mask	rw_devs[BCH_DATA_NR];
 	struct bch_tier		tiers[BCH_TIER_MAX];
 	/* NULL if we only have devices in one tier: */
+	struct bch_devs_mask	*fastest_devs;
 	struct bch_tier		*fastest_tier;
 
 	u64			capacity; /* sectors */
@@ -654,17 +623,17 @@ struct bch_fs {
 	struct io_clock		io_clock[2];
 
 	/* SECTOR ALLOCATOR */
-	struct list_head	open_buckets_open;
-	struct list_head	open_buckets_free;
-	unsigned		open_buckets_nr_free;
-	struct closure_waitlist	open_buckets_wait;
 	spinlock_t		open_buckets_lock;
+	u8			open_buckets_freelist;
+	u8			open_buckets_nr_free;
+	struct closure_waitlist	open_buckets_wait;
 	struct open_bucket	open_buckets[OPEN_BUCKETS_COUNT];
 
 	struct write_point	btree_write_point;
 
 	struct write_point	write_points[WRITE_POINT_COUNT];
-	struct write_point	promote_write_point;
+	struct hlist_head	write_points_hash[WRITE_POINT_COUNT];
+	struct mutex		write_points_hash_lock;
 
 	/*
 	 * This write point is used for migrating data off a device
diff --git a/libbcachefs/btree_cache.c b/libbcachefs/btree_cache.c
index 4147545d..22846d8a 100644
--- a/libbcachefs/btree_cache.c
+++ b/libbcachefs/btree_cache.c
@@ -31,13 +31,15 @@ void bch2_recalc_btree_reserve(struct bch_fs *c)
 			reserve += min_t(unsigned, 1,
 					 c->btree_roots[i].b->level) * 8;
 
-	c->btree_cache_reserve = reserve;
+	c->btree_cache.reserve = reserve;
 }
 
-#define mca_can_free(c)						\
-	max_t(int, 0, c->btree_cache_used - c->btree_cache_reserve)
+static inline unsigned btree_cache_can_free(struct btree_cache *bc)
+{
+	return max_t(int, 0, bc->used - bc->reserve);
+}
 
-static void __mca_data_free(struct bch_fs *c, struct btree *b)
+static void __btree_node_data_free(struct bch_fs *c, struct btree *b)
 {
 	EBUG_ON(btree_node_write_in_flight(b));
 
@@ -46,11 +48,13 @@ static void __mca_data_free(struct bch_fs *c, struct btree *b)
 	bch2_btree_keys_free(b);
 }
 
-static void mca_data_free(struct bch_fs *c, struct btree *b)
+static void btree_node_data_free(struct bch_fs *c, struct btree *b)
 {
-	__mca_data_free(c, b);
-	c->btree_cache_used--;
-	list_move(&b->list, &c->btree_cache_freed);
+	struct btree_cache *bc = &c->btree_cache;
+
+	__btree_node_data_free(c, b);
+	bc->used--;
+	list_move(&b->list, &bc->freed);
 }
 
 static const struct rhashtable_params bch_btree_cache_params = {
@@ -59,8 +63,10 @@ static const struct rhashtable_params bch_btree_cache_params = {
 	.key_len	= sizeof(struct bch_extent_ptr),
 };
 
-static void mca_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
+static void btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
 {
+	struct btree_cache *bc = &c->btree_cache;
+
 	b->data = kvpmalloc(btree_bytes(c), gfp);
 	if (!b->data)
 		goto err;
@@ -68,16 +74,16 @@ static void mca_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
 	if (bch2_btree_keys_alloc(b, btree_page_order(c), gfp))
 		goto err;
 
-	c->btree_cache_used++;
-	list_move(&b->list, &c->btree_cache_freeable);
+	bc->used++;
+	list_move(&b->list, &bc->freeable);
 	return;
 err:
 	kvpfree(b->data, btree_bytes(c));
 	b->data = NULL;
-	list_move(&b->list, &c->btree_cache_freed);
+	list_move(&b->list, &bc->freed);
 }
 
-static struct btree *mca_bucket_alloc(struct bch_fs *c, gfp_t gfp)
+static struct btree *btree_node_mem_alloc(struct bch_fs *c, gfp_t gfp)
 {
 	struct btree *b = kzalloc(sizeof(struct btree), gfp);
 	if (!b)
@@ -88,49 +94,48 @@ static struct btree *mca_bucket_alloc(struct bch_fs *c, gfp_t gfp)
 	INIT_LIST_HEAD(&b->list);
 	INIT_LIST_HEAD(&b->write_blocked);
 
-	mca_data_alloc(c, b, gfp);
+	btree_node_data_alloc(c, b, gfp);
 	return b->data ? b : NULL;
 }
 
 /* Btree in memory cache - hash table */
 
-void bch2_btree_node_hash_remove(struct bch_fs *c, struct btree *b)
+void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
 {
-	rhashtable_remove_fast(&c->btree_cache_table, &b->hash,
-			       bch_btree_cache_params);
+	rhashtable_remove_fast(&bc->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 __bch2_btree_node_hash_insert(struct bch_fs *c, struct btree *b)
+int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
 {
-	return rhashtable_lookup_insert_fast(&c->btree_cache_table, &b->hash,
+	return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
 					     bch_btree_cache_params);
 }
 
-int bch2_btree_node_hash_insert(struct bch_fs *c, struct btree *b,
-		    unsigned level, enum btree_id id)
+int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
+				unsigned level, enum btree_id id)
 {
 	int ret;
 
 	b->level	= level;
 	b->btree_id	= id;
 
-	mutex_lock(&c->btree_cache_lock);
-	ret = __bch2_btree_node_hash_insert(c, b);
+	mutex_lock(&bc->lock);
+	ret = __bch2_btree_node_hash_insert(bc, b);
 	if (!ret)
-		list_add(&b->list, &c->btree_cache);
-	mutex_unlock(&c->btree_cache_lock);
+		list_add(&b->list, &bc->live);
+	mutex_unlock(&bc->lock);
 
 	return ret;
 }
 
 __flatten
-static inline struct btree *mca_find(struct bch_fs *c,
+static inline struct btree *btree_cache_find(struct btree_cache *bc,
 				     const struct bkey_i *k)
 {
-	return rhashtable_lookup_fast(&c->btree_cache_table, &PTR_HASH(k),
+	return rhashtable_lookup_fast(&bc->table, &PTR_HASH(k),
 				      bch_btree_cache_params);
 }
 
@@ -140,9 +145,10 @@ static inline struct btree *mca_find(struct bch_fs *c,
  */
 static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	int ret = 0;
 
-	lockdep_assert_held(&c->btree_cache_lock);
+	lockdep_assert_held(&bc->lock);
 
 	if (!six_trylock_intent(&b->lock))
 		return -ENOMEM;
@@ -201,11 +207,12 @@ static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
 	return __btree_node_reclaim(c, b, true);
 }
 
-static unsigned long bch2_mca_scan(struct shrinker *shrink,
-				   struct shrink_control *sc)
+static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
+					   struct shrink_control *sc)
 {
 	struct bch_fs *c = container_of(shrink, struct bch_fs,
-					   btree_cache_shrink);
+					btree_cache.shrink);
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b, *t;
 	unsigned long nr = sc->nr_to_scan;
 	unsigned long can_free;
@@ -218,8 +225,8 @@ static unsigned long bch2_mca_scan(struct shrinker *shrink,
 
 	/* 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))
+		mutex_lock(&bc->lock);
+	else if (!mutex_trylock(&bc->lock))
 		return -1;
 
 	/*
@@ -230,11 +237,11 @@ static unsigned long bch2_mca_scan(struct shrinker *shrink,
 	 * IO can always make forward progress:
 	 */
 	nr /= btree_pages(c);
-	can_free = mca_can_free(c);
+	can_free = btree_cache_can_free(bc);
 	nr = min_t(unsigned long, nr, can_free);
 
 	i = 0;
-	list_for_each_entry_safe(b, t, &c->btree_cache_freeable, list) {
+	list_for_each_entry_safe(b, t, &bc->freeable, list) {
 		touched++;
 
 		if (freed >= nr)
@@ -242,34 +249,34 @@ static unsigned long bch2_mca_scan(struct shrinker *shrink,
 
 		if (++i > 3 &&
 		    !btree_node_reclaim(c, b)) {
-			mca_data_free(c, b);
+			btree_node_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) {
+	list_for_each_entry_safe(b, t, &bc->live, list) {
 		touched++;
 
 		if (freed >= nr) {
 			/* Save position */
-			if (&t->list != &c->btree_cache)
-				list_move_tail(&c->btree_cache, &t->list);
+			if (&t->list != &bc->live)
+				list_move_tail(&bc->live, &t->list);
 			break;
 		}
 
 		if (!btree_node_accessed(b) &&
 		    !btree_node_reclaim(c, b)) {
-			/* can't call bch2_btree_node_hash_remove under btree_cache_lock  */
+			/* can't call bch2_btree_node_hash_remove under lock  */
 			freed++;
-			if (&t->list != &c->btree_cache)
-				list_move_tail(&c->btree_cache, &t->list);
+			if (&t->list != &bc->live)
+				list_move_tail(&bc->live, &t->list);
 
-			mca_data_free(c, b);
-			mutex_unlock(&c->btree_cache_lock);
+			btree_node_data_free(c, b);
+			mutex_unlock(&bc->lock);
 
-			bch2_btree_node_hash_remove(c, b);
+			bch2_btree_node_hash_remove(bc, b);
 			six_unlock_write(&b->lock);
 			six_unlock_intent(&b->lock);
 
@@ -277,97 +284,97 @@ restart:
 				goto out;
 
 			if (sc->gfp_mask & __GFP_IO)
-				mutex_lock(&c->btree_cache_lock);
-			else if (!mutex_trylock(&c->btree_cache_lock))
+				mutex_lock(&bc->lock);
+			else if (!mutex_trylock(&bc->lock))
 				goto out;
 			goto restart;
 		} else
 			clear_btree_node_accessed(b);
 	}
 
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&bc->lock);
 out:
 	return (unsigned long) freed * btree_pages(c);
 }
 
-static unsigned long bch2_mca_count(struct shrinker *shrink,
-				    struct shrink_control *sc)
+static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
+					    struct shrink_control *sc)
 {
 	struct bch_fs *c = container_of(shrink, struct bch_fs,
-					   btree_cache_shrink);
+					btree_cache.shrink);
+	struct btree_cache *bc = &c->btree_cache;
 
 	if (btree_shrinker_disabled(c))
 		return 0;
 
-	return mca_can_free(c) * btree_pages(c);
+	return btree_cache_can_free(bc) * btree_pages(c);
 }
 
-void bch2_fs_btree_exit(struct bch_fs *c)
+void bch2_fs_btree_cache_exit(struct bch_fs *c)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 	unsigned i;
 
-	if (c->btree_cache_shrink.list.next)
-		unregister_shrinker(&c->btree_cache_shrink);
+	if (bc->shrink.list.next)
+		unregister_shrinker(&bc->shrink);
 
-	mutex_lock(&c->btree_cache_lock);
+	mutex_lock(&bc->lock);
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 	if (c->verify_data)
-		list_move(&c->verify_data->list, &c->btree_cache);
+		list_move(&c->verify_data->list, &bc->live);
 
 	kvpfree(c->verify_ondisk, btree_bytes(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_add(&c->btree_roots[i].b->list, &bc->live);
 
-	list_splice(&c->btree_cache_freeable,
-		    &c->btree_cache);
+	list_splice(&bc->freeable, &bc->live);
 
-	while (!list_empty(&c->btree_cache)) {
-		b = list_first_entry(&c->btree_cache, struct btree, list);
+	while (!list_empty(&bc->live)) {
+		b = list_first_entry(&bc->live, struct btree, list);
 
 		if (btree_node_dirty(b))
 			bch2_btree_complete_write(c, b, btree_current_write(b));
 		clear_btree_node_dirty(b);
 
-		mca_data_free(c, b);
+		btree_node_data_free(c, b);
 	}
 
-	while (!list_empty(&c->btree_cache_freed)) {
-		b = list_first_entry(&c->btree_cache_freed,
-				     struct btree, list);
+	while (!list_empty(&bc->freed)) {
+		b = list_first_entry(&bc->freed, struct btree, list);
 		list_del(&b->list);
 		kfree(b);
 	}
 
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&bc->lock);
 
-	if (c->btree_cache_table_init_done)
-		rhashtable_destroy(&c->btree_cache_table);
+	if (bc->table_init_done)
+		rhashtable_destroy(&bc->table);
 }
 
-int bch2_fs_btree_init(struct bch_fs *c)
+int bch2_fs_btree_cache_init(struct bch_fs *c)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	unsigned i;
 	int ret;
 
-	ret = rhashtable_init(&c->btree_cache_table, &bch_btree_cache_params);
+	ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
 	if (ret)
 		return ret;
 
-	c->btree_cache_table_init_done = true;
+	bc->table_init_done = true;
 
 	bch2_recalc_btree_reserve(c);
 
-	for (i = 0; i < c->btree_cache_reserve; i++)
-		if (!mca_bucket_alloc(c, GFP_KERNEL))
+	for (i = 0; i < bc->reserve; i++)
+		if (!btree_node_mem_alloc(c, GFP_KERNEL))
 			return -ENOMEM;
 
-	list_splice_init(&c->btree_cache,
-			 &c->btree_cache_freeable);
+	list_splice_init(&bc->live, &bc->freeable);
 
 #ifdef CONFIG_BCACHEFS_DEBUG
 	mutex_init(&c->verify_lock);
@@ -376,42 +383,53 @@ int bch2_fs_btree_init(struct bch_fs *c)
 	if (!c->verify_ondisk)
 		return -ENOMEM;
 
-	c->verify_data = mca_bucket_alloc(c, GFP_KERNEL);
+	c->verify_data = btree_node_mem_alloc(c, GFP_KERNEL);
 	if (!c->verify_data)
 		return -ENOMEM;
 
 	list_del_init(&c->verify_data->list);
 #endif
 
-	c->btree_cache_shrink.count_objects = bch2_mca_count;
-	c->btree_cache_shrink.scan_objects = bch2_mca_scan;
-	c->btree_cache_shrink.seeks = 4;
-	c->btree_cache_shrink.batch = btree_pages(c) * 2;
-	register_shrinker(&c->btree_cache_shrink);
+	bc->shrink.count_objects	= bch2_btree_cache_count;
+	bc->shrink.scan_objects		= bch2_btree_cache_scan;
+	bc->shrink.seeks		= 4;
+	bc->shrink.batch		= btree_pages(c) * 2;
+	register_shrinker(&bc->shrink);
 
 	return 0;
 }
 
+void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
+{
+	mutex_init(&bc->lock);
+	INIT_LIST_HEAD(&bc->live);
+	INIT_LIST_HEAD(&bc->freeable);
+	INIT_LIST_HEAD(&bc->freed);
+}
+
 /*
  * 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 bch2_btree_node_cannibalize_unlock(struct bch_fs *c)
+void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
 {
-	if (c->btree_cache_alloc_lock == current) {
+	struct btree_cache *bc = &c->btree_cache;
+
+	if (bc->alloc_lock == current) {
 		trace_btree_node_cannibalize_unlock(c);
-		c->btree_cache_alloc_lock = NULL;
-		closure_wake_up(&c->mca_wait);
+		bc->alloc_lock = NULL;
+		closure_wake_up(&bc->alloc_wait);
 	}
 }
 
-int bch2_btree_node_cannibalize_lock(struct bch_fs *c, struct closure *cl)
+int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct task_struct *old;
 
-	old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current);
+	old = cmpxchg(&bc->alloc_lock, NULL, current);
 	if (old == NULL || old == current)
 		goto success;
 
@@ -420,13 +438,13 @@ int bch2_btree_node_cannibalize_lock(struct bch_fs *c, struct closure *cl)
 		return -ENOMEM;
 	}
 
-	closure_wait(&c->mca_wait, cl);
+	closure_wait(&bc->alloc_wait, cl);
 
 	/* Try again, after adding ourselves to waitlist */
-	old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current);
+	old = cmpxchg(&bc->alloc_lock, NULL, current);
 	if (old == NULL || old == current) {
 		/* We raced */
-		closure_wake_up(&c->mca_wait);
+		closure_wake_up(&bc->alloc_wait);
 		goto success;
 	}
 
@@ -438,16 +456,17 @@ success:
 	return 0;
 }
 
-static struct btree *mca_cannibalize(struct bch_fs *c)
+static struct btree *btree_node_cannibalize(struct bch_fs *c)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 
-	list_for_each_entry_reverse(b, &c->btree_cache, list)
+	list_for_each_entry_reverse(b, &bc->live, list)
 		if (!btree_node_reclaim(c, b))
 			return b;
 
 	while (1) {
-		list_for_each_entry_reverse(b, &c->btree_cache, list)
+		list_for_each_entry_reverse(b, &bc->live, list)
 			if (!btree_node_write_and_reclaim(c, b))
 				return b;
 
@@ -462,16 +481,17 @@ static struct btree *mca_cannibalize(struct bch_fs *c)
 
 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 	u64 start_time = local_clock();
 
-	mutex_lock(&c->btree_cache_lock);
+	mutex_lock(&bc->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)
+	list_for_each_entry(b, &bc->freeable, list)
 		if (!btree_node_reclaim(c, b))
 			goto out_unlock;
 
@@ -479,9 +499,9 @@ struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
 	 * 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)
+	list_for_each_entry(b, &bc->freed, list)
 		if (!btree_node_reclaim(c, b)) {
-			mca_data_alloc(c, b, __GFP_NOWARN|GFP_NOIO);
+			btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_NOIO);
 			if (b->data)
 				goto out_unlock;
 
@@ -490,7 +510,7 @@ struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
 			goto err;
 		}
 
-	b = mca_bucket_alloc(c, __GFP_NOWARN|GFP_NOIO);
+	b = btree_node_mem_alloc(c, __GFP_NOWARN|GFP_NOIO);
 	if (!b)
 		goto err;
 
@@ -501,7 +521,7 @@ out_unlock:
 	BUG_ON(btree_node_write_in_flight(b));
 
 	list_del_init(&b->list);
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&bc->lock);
 out:
 	b->flags		= 0;
 	b->written		= 0;
@@ -517,18 +537,18 @@ out:
 	return b;
 err:
 	/* Try to cannibalize another cached btree node: */
-	if (c->btree_cache_alloc_lock == current) {
-		b = mca_cannibalize(c);
+	if (bc->alloc_lock == current) {
+		b = btree_node_cannibalize(c);
 		list_del_init(&b->list);
-		mutex_unlock(&c->btree_cache_lock);
+		mutex_unlock(&bc->lock);
 
-		bch2_btree_node_hash_remove(c, b);
+		bch2_btree_node_hash_remove(bc, b);
 
 		trace_btree_node_cannibalize(c);
 		goto out;
 	}
 
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&bc->lock);
 	return ERR_PTR(-ENOMEM);
 }
 
@@ -539,6 +559,7 @@ static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
 						   unsigned level,
 						   enum six_lock_type lock_type)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 
 	/*
@@ -552,15 +573,15 @@ static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
 		return b;
 
 	bkey_copy(&b->key, k);
-	if (bch2_btree_node_hash_insert(c, b, level, iter->btree_id)) {
+	if (bch2_btree_node_hash_insert(bc, 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);
+		mutex_lock(&bc->lock);
+		list_add(&b->list, &bc->freeable);
+		mutex_unlock(&bc->lock);
 
 		six_unlock_write(&b->lock);
 		six_unlock_intent(&b->lock);
@@ -601,13 +622,14 @@ struct btree *bch2_btree_node_get(struct bch_fs *c, struct btree_iter *iter,
 				  const struct bkey_i *k, unsigned level,
 				  enum six_lock_type lock_type)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 	struct bset_tree *t;
 
 	BUG_ON(level >= BTREE_MAX_DEPTH);
 retry:
 	rcu_read_lock();
-	b = mca_find(c, k);
+	b = btree_cache_find(bc, k);
 	rcu_read_unlock();
 
 	if (unlikely(!b)) {
@@ -755,12 +777,13 @@ struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
 void bch2_btree_node_prefetch(struct bch_fs *c, const struct bkey_i *k,
 			      unsigned level, enum btree_id btree_id)
 {
+	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b;
 
 	BUG_ON(level >= BTREE_MAX_DEPTH);
 
 	rcu_read_lock();
-	b = mca_find(c, k);
+	b = btree_cache_find(bc, k);
 	rcu_read_unlock();
 
 	if (b)
@@ -771,15 +794,15 @@ void bch2_btree_node_prefetch(struct bch_fs *c, const struct bkey_i *k,
 		return;
 
 	bkey_copy(&b->key, k);
-	if (bch2_btree_node_hash_insert(c, b, level, btree_id)) {
+	if (bch2_btree_node_hash_insert(bc, b, level, 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);
+		mutex_lock(&bc->lock);
+		list_add(&b->list, &bc->freeable);
+		mutex_unlock(&bc->lock);
 		goto out;
 	}
 
diff --git a/libbcachefs/btree_cache.h b/libbcachefs/btree_cache.h
index 5e836acd..46d536eb 100644
--- a/libbcachefs/btree_cache.h
+++ b/libbcachefs/btree_cache.h
@@ -11,13 +11,13 @@ extern const char * const bch2_btree_ids[];
 
 void bch2_recalc_btree_reserve(struct bch_fs *);
 
-void bch2_btree_node_hash_remove(struct bch_fs *, struct btree *);
-int __bch2_btree_node_hash_insert(struct bch_fs *, struct btree *);
-int bch2_btree_node_hash_insert(struct bch_fs *, struct btree *,
+void bch2_btree_node_hash_remove(struct btree_cache *, struct btree *);
+int __bch2_btree_node_hash_insert(struct btree_cache *, struct btree *);
+int bch2_btree_node_hash_insert(struct btree_cache *, struct btree *,
 				unsigned, enum btree_id);
 
-void bch2_btree_node_cannibalize_unlock(struct bch_fs *);
-int bch2_btree_node_cannibalize_lock(struct bch_fs *, struct closure *);
+void bch2_btree_cache_cannibalize_unlock(struct bch_fs *);
+int bch2_btree_cache_cannibalize_lock(struct bch_fs *, struct closure *);
 
 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *);
 
@@ -32,8 +32,9 @@ struct btree *bch2_btree_node_get_sibling(struct bch_fs *, struct btree_iter *,
 void bch2_btree_node_prefetch(struct bch_fs *, const struct bkey_i *,
 			      unsigned, enum btree_id);
 
-void bch2_fs_btree_exit(struct bch_fs *);
-int bch2_fs_btree_init(struct bch_fs *);
+void bch2_fs_btree_cache_exit(struct bch_fs *);
+int bch2_fs_btree_cache_init(struct bch_fs *);
+void bch2_fs_btree_cache_init_early(struct btree_cache *);
 
 #define PTR_HASH(_k)	(bkey_i_to_extent_c(_k)->v._data[0])
 
diff --git a/libbcachefs/btree_gc.c b/libbcachefs/btree_gc.c
index e5cc00cc..b0901965 100644
--- a/libbcachefs/btree_gc.c
+++ b/libbcachefs/btree_gc.c
@@ -278,9 +278,12 @@ static void bch2_mark_allocator_buckets(struct bch_fs *c)
 {
 	struct bch_dev *ca;
 	struct open_bucket *ob;
+	const struct open_bucket_ptr *ptr;
 	size_t i, j, iter;
 	unsigned ci;
 
+	down_write(&c->alloc_gc_lock);
+
 	for_each_member_device(ca, c, ci) {
 		spin_lock(&ca->freelist_lock);
 
@@ -291,21 +294,26 @@ static void bch2_mark_allocator_buckets(struct bch_fs *c)
 			fifo_for_each_entry(i, &ca->free[j], iter)
 				bch2_mark_alloc_bucket(ca, &ca->buckets[i], true);
 
+		for (ptr = ca->open_buckets_partial;
+		     ptr < ca->open_buckets_partial + ca->open_buckets_partial_nr;
+		     ptr++)
+			bch2_mark_alloc_bucket(ca, PTR_BUCKET(ca, &ptr->ptr), true);
+
 		spin_unlock(&ca->freelist_lock);
 	}
 
 	for (ob = c->open_buckets;
 	     ob < c->open_buckets + ARRAY_SIZE(c->open_buckets);
 	     ob++) {
-		const struct bch_extent_ptr *ptr;
-
-		mutex_lock(&ob->lock);
+		spin_lock(&ob->lock);
 		open_bucket_for_each_ptr(ob, ptr) {
-			ca = c->devs[ptr->dev];
-			bch2_mark_alloc_bucket(ca, PTR_BUCKET(ca, ptr), true);
+			ca = c->devs[ptr->ptr.dev];
+			bch2_mark_alloc_bucket(ca, PTR_BUCKET(ca, &ptr->ptr), true);
 		}
-		mutex_unlock(&ob->lock);
+		spin_unlock(&ob->lock);
 	}
+
+	up_write(&c->alloc_gc_lock);
 }
 
 static void mark_metadata_sectors(struct bch_dev *ca, u64 start, u64 end,
diff --git a/libbcachefs/btree_io.c b/libbcachefs/btree_io.c
index 507a6a9d..d50e9e8e 100644
--- a/libbcachefs/btree_io.c
+++ b/libbcachefs/btree_io.c
@@ -1364,17 +1364,17 @@ int bch2_btree_root_read(struct bch_fs *c, enum btree_id id,
 	closure_init_stack(&cl);
 
 	do {
-		ret = bch2_btree_node_cannibalize_lock(c, &cl);
+		ret = bch2_btree_cache_cannibalize_lock(c, &cl);
 		closure_sync(&cl);
 	} while (ret);
 
 	b = bch2_btree_node_mem_alloc(c);
-	bch2_btree_node_cannibalize_unlock(c);
+	bch2_btree_cache_cannibalize_unlock(c);
 
 	BUG_ON(IS_ERR(b));
 
 	bkey_copy(&b->key, k);
-	BUG_ON(bch2_btree_node_hash_insert(c, b, level, id));
+	BUG_ON(bch2_btree_node_hash_insert(&c->btree_cache, b, level, id));
 
 	bch2_btree_node_read(c, b, true);
 	six_unlock_write(&b->lock);
@@ -1844,8 +1844,8 @@ void bch2_btree_verify_flushed(struct bch_fs *c)
 	unsigned i;
 
 	rcu_read_lock();
-	tbl = rht_dereference_rcu(c->btree_cache_table.tbl,
-				  &c->btree_cache_table);
+	tbl = rht_dereference_rcu(c->btree_cache.table.tbl,
+				  &c->btree_cache.table);
 
 	for (i = 0; i < tbl->size; i++)
 		rht_for_each_entry_rcu(b, pos, tbl, i, hash)
diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index b1b62339..b0e64957 100644
--- a/libbcachefs/btree_iter.c
+++ b/libbcachefs/btree_iter.c
@@ -769,7 +769,7 @@ retry_all:
 		closure_init_stack(&cl);
 
 		do {
-			ret = bch2_btree_node_cannibalize_lock(c, &cl);
+			ret = bch2_btree_cache_cannibalize_lock(c, &cl);
 			closure_sync(&cl);
 		} while (ret);
 	}
@@ -817,7 +817,7 @@ retry:
 
 	ret = btree_iter_linked(iter) ? -EINTR : 0;
 out:
-	bch2_btree_node_cannibalize_unlock(c);
+	bch2_btree_cache_cannibalize_unlock(c);
 	return ret;
 io_error:
 	BUG_ON(ret != -EIO);
diff --git a/libbcachefs/btree_types.h b/libbcachefs/btree_types.h
index c0c16205..8b4df034 100644
--- a/libbcachefs/btree_types.h
+++ b/libbcachefs/btree_types.h
@@ -130,6 +130,42 @@ struct btree {
 #endif
 };
 
+struct btree_cache {
+	struct rhashtable	table;
+	bool			table_init_done;
+	/*
+	 * We never free a struct btree, except on shutdown - we just put it on
+	 * the btree_cache_freed list and reuse it later. This simplifies the
+	 * code, and it doesn't cost us much memory as the memory usage is
+	 * dominated by buffers that hold the actual btree node data and those
+	 * can be freed - and the number of struct btrees allocated is
+	 * effectively bounded.
+	 *
+	 * btree_cache_freeable effectively is a small cache - we use it because
+	 * high order page allocations can be rather expensive, and it's quite
+	 * common to delete and allocate btree nodes in quick succession. It
+	 * should never grow past ~2-3 nodes in practice.
+	 */
+	struct mutex		lock;
+	struct list_head	live;
+	struct list_head	freeable;
+	struct list_head	freed;
+
+	/* Number of elements in live + freeable lists */
+	unsigned		used;
+	unsigned		reserve;
+	struct shrinker		shrink;
+
+	/*
+	 * If we need to allocate memory for a new btree node and that
+	 * allocation fails, we can cannibalize another node in the btree cache
+	 * to satisfy the allocation - lock to guarantee only one thread does
+	 * this at a time:
+	 */
+	struct task_struct	*alloc_lock;
+	struct closure_waitlist	alloc_wait;
+};
+
 #define BTREE_FLAG(flag)						\
 static inline bool btree_node_ ## flag(struct btree *b)			\
 {	return test_bit(BTREE_NODE_ ## flag, &b->flags); }		\
diff --git a/libbcachefs/btree_update_interior.c b/libbcachefs/btree_update_interior.c
index 922a4863..2efb01c1 100644
--- a/libbcachefs/btree_update_interior.c
+++ b/libbcachefs/btree_update_interior.c
@@ -237,11 +237,11 @@ static void __btree_node_free(struct bch_fs *c, struct btree *b,
 
 	six_lock_write(&b->lock);
 
-	bch2_btree_node_hash_remove(c, b);
+	bch2_btree_node_hash_remove(&c->btree_cache, b);
 
-	mutex_lock(&c->btree_cache_lock);
-	list_move(&b->list, &c->btree_cache_freeable);
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_lock(&c->btree_cache.lock);
+	list_move(&b->list, &c->btree_cache.freeable);
+	mutex_unlock(&c->btree_cache.lock);
 
 	/*
 	 * By using six_unlock_write() directly instead of
@@ -339,11 +339,11 @@ retry:
 	bkey_extent_init(&tmp.k);
 	tmp.k.k.size = c->opts.btree_node_size,
 
-	ob = bch2_alloc_sectors(c, &c->btree_write_point,
-			       bkey_i_to_extent(&tmp.k),
-			       res->nr_replicas,
-			       c->opts.metadata_replicas_required,
-			       alloc_reserve, cl);
+	ob = bch2_alloc_sectors(c, BCH_DATA_BTREE, 0, 0,
+				bkey_i_to_extent(&tmp.k),
+				res->nr_replicas,
+				c->opts.metadata_replicas_required,
+				alloc_reserve, 0, cl);
 	if (IS_ERR(ob))
 		return ERR_CAST(ob);
 
@@ -374,7 +374,7 @@ static struct btree *bch2_btree_node_alloc(struct btree_update *as, unsigned lev
 
 	b = as->reserve->b[--as->reserve->nr];
 
-	BUG_ON(bch2_btree_node_hash_insert(c, b, level, as->btree_id));
+	BUG_ON(bch2_btree_node_hash_insert(&c->btree_cache, b, level, as->btree_id));
 
 	set_btree_node_accessed(b);
 	set_btree_node_dirty(b);
@@ -515,7 +515,7 @@ static struct btree_reserve *bch2_btree_reserve_get(struct bch_fs *c,
 	 * Protects reaping from the btree node cache and using the btree node
 	 * open bucket reserve:
 	 */
-	ret = bch2_btree_node_cannibalize_lock(c, cl);
+	ret = bch2_btree_cache_cannibalize_lock(c, cl);
 	if (ret) {
 		bch2_disk_reservation_put(c, &disk_res);
 		return ERR_PTR(ret);
@@ -543,11 +543,11 @@ static struct btree_reserve *bch2_btree_reserve_get(struct bch_fs *c,
 		reserve->b[reserve->nr++] = b;
 	}
 
-	bch2_btree_node_cannibalize_unlock(c);
+	bch2_btree_cache_cannibalize_unlock(c);
 	return reserve;
 err_free:
 	bch2_btree_reserve_put(c, reserve);
-	bch2_btree_node_cannibalize_unlock(c);
+	bch2_btree_cache_cannibalize_unlock(c);
 	trace_btree_reserve_get_fail(c, nr_nodes, cl);
 	return ERR_PTR(ret);
 }
@@ -1015,9 +1015,9 @@ bch2_btree_update_start(struct bch_fs *c, enum btree_id id,
 static void __bch2_btree_set_root_inmem(struct bch_fs *c, struct btree *b)
 {
 	/* Root nodes cannot be reaped */
-	mutex_lock(&c->btree_cache_lock);
+	mutex_lock(&c->btree_cache.lock);
 	list_del_init(&b->list);
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&c->btree_cache.lock);
 
 	mutex_lock(&c->btree_root_lock);
 	btree_node_root(c, b) = b;
@@ -1802,7 +1802,7 @@ retry:
 	    PTR_HASH(&new_key->k_i) != PTR_HASH(&b->key)) {
 		/* bch2_btree_reserve_get will unlock */
 		do {
-			ret = bch2_btree_node_cannibalize_lock(c, &cl);
+			ret = bch2_btree_cache_cannibalize_lock(c, &cl);
 			closure_sync(&cl);
 		} while (ret == -EAGAIN);
 
@@ -1873,23 +1873,24 @@ retry:
 	if (parent) {
 		if (new_hash) {
 			bkey_copy(&new_hash->key, &new_key->k_i);
-			BUG_ON(bch2_btree_node_hash_insert(c, new_hash,
-							b->level, b->btree_id));
+			ret = bch2_btree_node_hash_insert(&c->btree_cache,
+					new_hash, b->level, b->btree_id);
+			BUG_ON(ret);
 		}
 
 		bch2_btree_insert_node(as, parent, &iter,
 				       &keylist_single(&new_key->k_i));
 
 		if (new_hash) {
-			mutex_lock(&c->btree_cache_lock);
-			bch2_btree_node_hash_remove(c, new_hash);
+			mutex_lock(&c->btree_cache.lock);
+			bch2_btree_node_hash_remove(&c->btree_cache, new_hash);
 
-			bch2_btree_node_hash_remove(c, b);
+			bch2_btree_node_hash_remove(&c->btree_cache, b);
 
 			bkey_copy(&b->key, &new_key->k_i);
-			ret = __bch2_btree_node_hash_insert(c, b);
+			ret = __bch2_btree_node_hash_insert(&c->btree_cache, b);
 			BUG_ON(ret);
-			mutex_unlock(&c->btree_cache_lock);
+			mutex_unlock(&c->btree_cache.lock);
 		} else {
 			bkey_copy(&b->key, &new_key->k_i);
 		}
@@ -1918,9 +1919,9 @@ retry:
 	bch2_btree_update_done(as);
 out:
 	if (new_hash) {
-		mutex_lock(&c->btree_cache_lock);
-		list_move(&new_hash->list, &c->btree_cache_freeable);
-		mutex_unlock(&c->btree_cache_lock);
+		mutex_lock(&c->btree_cache.lock);
+		list_move(&new_hash->list, &c->btree_cache.freeable);
+		mutex_unlock(&c->btree_cache.lock);
 
 		six_unlock_write(&new_hash->lock);
 		six_unlock_intent(&new_hash->lock);
diff --git a/libbcachefs/buckets.c b/libbcachefs/buckets.c
index fbc31012..6fdbb464 100644
--- a/libbcachefs/buckets.c
+++ b/libbcachefs/buckets.c
@@ -407,8 +407,11 @@ void bch2_mark_metadata_bucket(struct bch_dev *ca, struct bucket *g,
 
 static int __disk_sectors(const union bch_extent_crc *crc, unsigned sectors)
 {
-	return sectors * crc_compressed_size(NULL, crc) /
-		crc_uncompressed_size(NULL, crc);
+	if (!sectors)
+		return 0;
+
+	return max(1U, DIV_ROUND_UP(sectors * crc_compressed_size(NULL, crc),
+				    crc_uncompressed_size(NULL, crc)));
 }
 
 /*
diff --git a/libbcachefs/compress.c b/libbcachefs/compress.c
index c8a03c7f..7b45bb78 100644
--- a/libbcachefs/compress.c
+++ b/libbcachefs/compress.c
@@ -25,7 +25,7 @@ static struct bbuf __bounce_alloc(struct bch_fs *c, unsigned size, int rw)
 {
 	void *b;
 
-	BUG_ON(size > c->sb.encoded_extent_max);
+	BUG_ON(size > c->sb.encoded_extent_max << 9);
 
 	b = kmalloc(size, GFP_NOIO|__GFP_NOWARN);
 	if (b)
@@ -164,8 +164,8 @@ static int __bio_uncompress(struct bch_fs *c, struct bio *src,
 		}
 		break;
 	case BCH_COMPRESSION_LZ4:
-		ret = LZ4_decompress_safe(src_data.b, dst_data,
-					  src_len, dst_len);
+		ret = LZ4_decompress_safe_partial(src_data.b, dst_data,
+						  src_len, dst_len, dst_len);
 		if (ret != dst_len) {
 			ret = -EIO;
 			goto err;
@@ -269,7 +269,8 @@ int bch2_bio_uncompress(struct bch_fs *c, struct bio *src,
 	size_t dst_len = crc_uncompressed_size(NULL, &crc) << 9;
 	int ret = -ENOMEM;
 
-	if (crc_uncompressed_size(NULL, &crc) < c->sb.encoded_extent_max)
+	if (crc_uncompressed_size(NULL, &crc) > c->sb.encoded_extent_max ||
+	    crc_compressed_size(NULL, &crc)   > c->sb.encoded_extent_max)
 		return -EIO;
 
 	dst_data = dst_len == dst_iter.bi_size
@@ -294,7 +295,7 @@ static int __bio_compress(struct bch_fs *c,
 {
 	struct bbuf src_data = { NULL }, dst_data = { NULL };
 	unsigned pad;
-	int ret;
+	int ret = 0;
 
 	dst_data = bio_map_or_bounce(c, dst, WRITE);
 	src_data = bio_map_or_bounce(c, src, READ);
@@ -307,23 +308,28 @@ static int __bio_compress(struct bch_fs *c,
 		void *workspace;
 		int len = src->bi_iter.bi_size;
 
-		ret = 0;
-
 		workspace = mempool_alloc(&c->lz4_workspace_pool, GFP_NOIO);
 
-		while (len > block_bytes(c) &&
-		       (!(ret = LZ4_compress_destSize(
+		while (1) {
+			if (len <= block_bytes(c)) {
+				ret = 0;
+				break;
+			}
+
+			ret = LZ4_compress_destSize(
 					src_data.b,	dst_data.b,
 					&len,		dst->bi_iter.bi_size,
-					workspace)) ||
-			(len & (block_bytes(c) - 1)))) {
-			/*
-			 * On error, the compressed data was bigger than
-			 * dst_len - round down to nearest block and try again:
-			 */
+					workspace);
+			if (ret >= len) {
+				/* uncompressible: */
+				ret = 0;
+				break;
+			}
+
+			if (!(len & (block_bytes(c) - 1)))
+				break;
 			len = round_down(len, block_bytes(c));
 		}
-
 		mempool_free(workspace, &c->lz4_workspace_pool);
 
 		if (!ret)
@@ -331,6 +337,7 @@ static int __bio_compress(struct bch_fs *c,
 
 		*src_len = len;
 		*dst_len = ret;
+		ret = 0;
 		break;
 	}
 	case BCH_COMPRESSION_GZIP: {
@@ -446,20 +453,22 @@ int bch2_check_set_has_compressed_data(struct bch_fs *c,
 				      unsigned compression_type)
 {
 	switch (compression_type) {
-	case BCH_COMPRESSION_NONE:
+	case BCH_COMPRESSION_OPT_NONE:
 		return 0;
-	case BCH_COMPRESSION_LZ4:
+	case BCH_COMPRESSION_OPT_LZ4:
 		if (bch2_sb_test_feature(c->disk_sb, BCH_FEATURE_LZ4))
 			return 0;
 
 		bch2_sb_set_feature(c->disk_sb, BCH_FEATURE_LZ4);
 		break;
-	case BCH_COMPRESSION_GZIP:
+	case BCH_COMPRESSION_OPT_GZIP:
 		if (bch2_sb_test_feature(c->disk_sb, BCH_FEATURE_GZIP))
 			return 0;
 
 		bch2_sb_set_feature(c->disk_sb, BCH_FEATURE_GZIP);
 		break;
+	default:
+		BUG();
 	}
 
 	return bch2_fs_compress_init(c);
diff --git a/libbcachefs/extents.c b/libbcachefs/extents.c
index 1937f4cb..7d2f5ccb 100644
--- a/libbcachefs/extents.c
+++ b/libbcachefs/extents.c
@@ -511,19 +511,19 @@ static void extent_pick_read_device(struct bch_fs *c,
 		struct bch_dev *ca = c->devs[ptr->dev];
 
 		if (ptr->cached && ptr_stale(ca, ptr))
-			return;
+			continue;
 
 		if (ca->mi.state == BCH_MEMBER_STATE_FAILED)
-			return;
+			continue;
 
 		if (avoid && test_bit(ca->dev_idx, avoid->d))
-			return;
+			continue;
 
 		if (pick->ca && pick->ca->mi.tier < ca->mi.tier)
-			return;
+			continue;
 
 		if (!percpu_ref_tryget(&ca->io_ref))
-			return;
+			continue;
 
 		if (pick->ca)
 			percpu_ref_put(&pick->ca->io_ref);
diff --git a/libbcachefs/fs-io.c b/libbcachefs/fs-io.c
index 5eb62f9d..8b41be87 100644
--- a/libbcachefs/fs-io.c
+++ b/libbcachefs/fs-io.c
@@ -974,7 +974,8 @@ alloc_io:
 				(struct disk_reservation) {
 					.nr_replicas = c->opts.data_replicas,
 				},
-				foreground_write_point(c, inode->ei_last_dirtied),
+				c->fastest_devs,
+				inode->ei_last_dirtied,
 				POS(inum, 0),
 				&inode->ei_journal_seq,
 				BCH_WRITE_THROTTLE);
@@ -1545,10 +1546,11 @@ static void bch2_do_direct_IO_write(struct dio_write *dio)
 	dio->iop.is_dio		= true;
 	dio->iop.new_i_size	= U64_MAX;
 	bch2_write_op_init(&dio->iop.op, dio->c, dio->res,
-			foreground_write_point(dio->c, (unsigned long) current),
-			POS(inode->v.i_ino, (dio->offset + dio->written) >> 9),
-			&inode->ei_journal_seq,
-			flags|BCH_WRITE_THROTTLE);
+			   dio->c->fastest_devs,
+			   (unsigned long) dio->task,
+			   POS(inode->v.i_ino, (dio->offset + dio->written) >> 9),
+			   &inode->ei_journal_seq,
+			   flags|BCH_WRITE_THROTTLE);
 	dio->iop.op.index_update_fn = bchfs_write_index_update;
 
 	dio->res.sectors -= bio_sectors(bio);
@@ -1568,13 +1570,13 @@ static void bch2_dio_write_loop_async(struct closure *cl)
 	bch2_dio_write_done(dio);
 
 	if (dio->iter.count && !dio->error) {
-		use_mm(dio->mm);
+		use_mm(dio->task->mm);
 		pagecache_block_get(&mapping->add_lock);
 
 		bch2_do_direct_IO_write(dio);
 
 		pagecache_block_put(&mapping->add_lock);
-		unuse_mm(dio->mm);
+		unuse_mm(dio->task->mm);
 
 		continue_at(&dio->cl, bch2_dio_write_loop_async, NULL);
 	} else {
@@ -1617,7 +1619,7 @@ static int bch2_direct_IO_write(struct bch_fs *c,
 	dio->offset	= offset;
 	dio->iovec	= NULL;
 	dio->iter	= *iter;
-	dio->mm		= current->mm;
+	dio->task	= current;
 	closure_init(&dio->cl, NULL);
 
 	if (offset + iter->count > inode->v.i_size)
diff --git a/libbcachefs/fs-io.h b/libbcachefs/fs-io.h
index dfdc9b52..505cea73 100644
--- a/libbcachefs/fs-io.h
+++ b/libbcachefs/fs-io.h
@@ -74,7 +74,7 @@ struct dio_write {
 	struct iovec			inline_vecs[UIO_FASTIOV];
 	struct iov_iter			iter;
 
-	struct mm_struct		*mm;
+	struct task_struct		*task;
 
 	/* must be last: */
 	struct bchfs_write_op		iop;
diff --git a/libbcachefs/io.c b/libbcachefs/io.c
index 946c75bb..e5fc72da 100644
--- a/libbcachefs/io.c
+++ b/libbcachefs/io.c
@@ -350,7 +350,7 @@ static void init_append_extent(struct bch_write_op *op,
 	bch2_keylist_push(&op->insert_keys);
 }
 
-static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
+static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp)
 {
 	struct bch_fs *c = op->c;
 	struct bio *orig = &op->wbio.bio;
@@ -371,7 +371,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
 	/* Need to decompress data? */
 	if ((op->flags & BCH_WRITE_DATA_COMPRESSED) &&
 	    (crc_uncompressed_size(NULL, &op->crc) != op->size ||
-	     crc_compressed_size(NULL, &op->crc) > ob->sectors_free)) {
+	     crc_compressed_size(NULL, &op->crc) > wp->sectors_free)) {
 		int ret;
 
 		ret = bch2_bio_uncompress_inplace(c, orig, op->size, op->crc);
@@ -389,7 +389,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
 				   op->crc.nonce,
 				   op->crc.csum,
 				   op->crc.csum_type,
-				   ob);
+				   wp->ob);
 
 		bio			= orig;
 		wbio			= wbio_init(bio);
@@ -398,7 +398,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
 		   compression_type != BCH_COMPRESSION_NONE) {
 		/* all units here in bytes */
 		unsigned total_output = 0, output_available =
-			min(ob->sectors_free << 9, orig->bi_iter.bi_size);
+			min(wp->sectors_free << 9, orig->bi_iter.bi_size);
 		unsigned crc_nonce = bch2_csum_type_is_encryption(csum_type)
 			? op->nonce : 0;
 		struct bch_csum csum;
@@ -441,7 +441,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
 			init_append_extent(op,
 					   dst_len >> 9, src_len >> 9,
 					   fragment_compression_type,
-					   crc_nonce, csum, csum_type, ob);
+					   crc_nonce, csum, csum_type, wp->ob);
 
 			total_output += dst_len;
 			bio_advance(bio, dst_len);
@@ -468,14 +468,14 @@ static int bch2_write_extent(struct bch_write_op *op, struct open_bucket *ob)
 
 		more = orig->bi_iter.bi_size != 0;
 	} else {
-		bio = bio_next_split(orig, ob->sectors_free, GFP_NOIO,
+		bio = bio_next_split(orig, wp->sectors_free, GFP_NOIO,
 				     &c->bio_write);
 		wbio			= wbio_init(bio);
 		wbio->put_bio		= bio != orig;
 
 		init_append_extent(op, bio_sectors(bio), bio_sectors(bio),
 				   compression_type, 0,
-				   (struct bch_csum) { 0 }, csum_type, ob);
+				   (struct bch_csum) { 0 }, csum_type, wp->ob);
 
 		more = bio != orig;
 	}
@@ -505,7 +505,8 @@ static void __bch2_write(struct closure *cl)
 	struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
 	struct bch_fs *c = op->c;
 	unsigned open_bucket_nr = 0;
-	struct open_bucket *b;
+	struct write_point *wp;
+	struct open_bucket *ob;
 	int ret;
 
 	do {
@@ -519,16 +520,19 @@ static void __bch2_write(struct closure *cl)
 					BKEY_EXTENT_U64s_MAX))
 			continue_at(cl, bch2_write_index, index_update_wq(op));
 
-		b = bch2_alloc_sectors_start(c, op->wp,
+		wp = bch2_alloc_sectors_start(c, BCH_DATA_USER,
+			op->devs,
+			op->write_point,
 			op->nr_replicas,
 			c->opts.data_replicas_required,
 			op->alloc_reserve,
+			op->flags,
 			(op->flags & BCH_WRITE_ALLOC_NOWAIT) ? NULL : cl);
-		EBUG_ON(!b);
+		EBUG_ON(!wp);
 
-		if (unlikely(IS_ERR(b))) {
-			if (unlikely(PTR_ERR(b) != -EAGAIN)) {
-				ret = PTR_ERR(b);
+		if (unlikely(IS_ERR(wp))) {
+			if (unlikely(PTR_ERR(wp) != -EAGAIN)) {
+				ret = PTR_ERR(wp);
 				goto err;
 			}
 
@@ -561,13 +565,15 @@ static void __bch2_write(struct closure *cl)
 			continue;
 		}
 
-		BUG_ON(b - c->open_buckets == 0 ||
-		       b - c->open_buckets > U8_MAX);
-		op->open_buckets[open_bucket_nr++] = b - c->open_buckets;
+		ob = wp->ob;
 
-		ret = bch2_write_extent(op, b);
+		BUG_ON(ob - c->open_buckets == 0 ||
+		       ob - c->open_buckets > U8_MAX);
+		op->open_buckets[open_bucket_nr++] = ob - c->open_buckets;
 
-		bch2_alloc_sectors_done(c, op->wp, b);
+		ret = bch2_write_extent(op, wp);
+
+		bch2_alloc_sectors_done(c, wp);
 
 		if (ret < 0)
 			goto err;
@@ -704,7 +710,9 @@ void bch2_write(struct closure *cl)
 
 void bch2_write_op_init(struct bch_write_op *op, struct bch_fs *c,
 			struct disk_reservation res,
-			struct write_point *wp, struct bpos pos,
+			struct bch_devs_mask *devs,
+			unsigned long write_point,
+			struct bpos pos,
 			u64 *journal_seq, unsigned flags)
 {
 	EBUG_ON(res.sectors && !res.nr_replicas);
@@ -723,7 +731,8 @@ void bch2_write_op_init(struct bch_write_op *op, struct bch_fs *c,
 	op->pos		= pos;
 	op->version	= ZERO_VERSION;
 	op->res		= res;
-	op->wp		= wp;
+	op->devs	= devs;
+	op->write_point	= write_point;
 
 	if (journal_seq) {
 		op->journal_seq_p = journal_seq;
@@ -826,6 +835,7 @@ static struct promote_op *promote_alloc(struct bch_fs *c,
 		 * Adjust bio to correspond to _live_ portion of @k -
 		 * which might be less than what we're actually reading:
 		 */
+		bio->bi_iter.bi_size = sectors << 9;
 		bio_advance(bio, pick->crc.offset << 9);
 		BUG_ON(bio_sectors(bio) < k.k->size);
 		bio->bi_iter.bi_size = k.k->size << 9;
@@ -836,7 +846,8 @@ static struct promote_op *promote_alloc(struct bch_fs *c,
 		 */
 		op->write.op.pos.offset = iter.bi_sector;
 	}
-	bch2_migrate_write_init(c, &op->write, &c->promote_write_point,
+	bch2_migrate_write_init(c, &op->write,
+				c->fastest_devs,
 				k, NULL,
 				BCH_WRITE_ALLOC_NOWAIT|
 				BCH_WRITE_CACHED);
diff --git a/libbcachefs/io.h b/libbcachefs/io.h
index 674cdf7a..658c15a5 100644
--- a/libbcachefs/io.h
+++ b/libbcachefs/io.h
@@ -22,11 +22,12 @@ enum bch_write_flags {
 	BCH_WRITE_FLUSH			= (1 << 2),
 	BCH_WRITE_DATA_COMPRESSED	= (1 << 3),
 	BCH_WRITE_THROTTLE		= (1 << 4),
+	BCH_WRITE_ONLY_SPECIFIED_DEVS	= (1 << 5),
 
 	/* Internal: */
-	BCH_WRITE_JOURNAL_SEQ_PTR	= (1 << 5),
-	BCH_WRITE_DONE			= (1 << 6),
-	BCH_WRITE_LOOPED		= (1 << 7),
+	BCH_WRITE_JOURNAL_SEQ_PTR	= (1 << 6),
+	BCH_WRITE_DONE			= (1 << 7),
+	BCH_WRITE_LOOPED		= (1 << 8),
 };
 
 static inline u64 *op_journal_seq(struct bch_write_op *op)
@@ -35,15 +36,10 @@ static inline u64 *op_journal_seq(struct bch_write_op *op)
 		? op->journal_seq_p : &op->journal_seq;
 }
 
-static inline struct write_point *foreground_write_point(struct bch_fs *c,
-							 unsigned long v)
-{
-	return c->write_points +
-		hash_long(v, ilog2(ARRAY_SIZE(c->write_points)));
-}
-
 void bch2_write_op_init(struct bch_write_op *, struct bch_fs *,
-			struct disk_reservation, struct write_point *,
+			struct disk_reservation,
+			struct bch_devs_mask *,
+			unsigned long,
 			struct bpos, u64 *, unsigned);
 void bch2_write(struct closure *);
 
diff --git a/libbcachefs/io_types.h b/libbcachefs/io_types.h
index ae4f8f3c..f77106be 100644
--- a/libbcachefs/io_types.h
+++ b/libbcachefs/io_types.h
@@ -116,9 +116,10 @@ struct bch_write_op {
 	struct bch_extent_crc128 crc;
 	unsigned		size;
 
-	struct disk_reservation	res;
+	struct bch_devs_mask	*devs;
+	unsigned long		write_point;
 
-	struct write_point	*wp;
+	struct disk_reservation	res;
 
 	union {
 	u8			open_buckets[16];
diff --git a/libbcachefs/migrate.c b/libbcachefs/migrate.c
index c6659259..d7f27a3d 100644
--- a/libbcachefs/migrate.c
+++ b/libbcachefs/migrate.c
@@ -15,6 +15,7 @@
 
 static int issue_migration_move(struct bch_dev *ca,
 				struct moving_context *ctxt,
+				struct bch_devs_mask *devs,
 				struct bkey_s_c k)
 {
 	struct bch_fs *c = ca->fs;
@@ -33,7 +34,7 @@ static int issue_migration_move(struct bch_dev *ca,
 found:
 	/* XXX: we need to be doing something with the disk reservation */
 
-	ret = bch2_data_move(c, ctxt, &c->migration_write_point, k, ptr);
+	ret = bch2_data_move(c, ctxt, devs, k, ptr);
 	if (ret)
 		bch2_disk_reservation_put(c, &res);
 	return ret;
@@ -110,7 +111,7 @@ int bch2_move_data_off_device(struct bch_dev *ca)
 						   ca->dev_idx))
 				goto next;
 
-			ret = issue_migration_move(ca, &ctxt, k);
+			ret = issue_migration_move(ca, &ctxt, NULL, k);
 			if (ret == -ENOMEM) {
 				bch2_btree_iter_unlock(&iter);
 
diff --git a/libbcachefs/move.c b/libbcachefs/move.c
index f78cd72f..0c5b924c 100644
--- a/libbcachefs/move.c
+++ b/libbcachefs/move.c
@@ -139,7 +139,7 @@ out:
 
 void bch2_migrate_write_init(struct bch_fs *c,
 			     struct migrate_write *m,
-			     struct write_point *wp,
+			     struct bch_devs_mask *devs,
 			     struct bkey_s_c k,
 			     const struct bch_extent_ptr *move_ptr,
 			     unsigned flags)
@@ -155,8 +155,10 @@ void bch2_migrate_write_init(struct bch_fs *c,
 	    (move_ptr && move_ptr->cached))
 		flags |= BCH_WRITE_CACHED;
 
-	bch2_write_op_init(&m->op, c, (struct disk_reservation) { 0 }, wp,
-			  bkey_start_pos(k.k), NULL, flags);
+	bch2_write_op_init(&m->op, c, (struct disk_reservation) { 0 },
+			   devs, (unsigned long) current,
+			   bkey_start_pos(k.k), NULL,
+			   flags|BCH_WRITE_ONLY_SPECIFIED_DEVS);
 
 	if (m->move)
 		m->op.alloc_reserve = RESERVE_MOVINGGC;
@@ -249,7 +251,7 @@ static void read_moving_endio(struct bio *bio)
 
 int bch2_data_move(struct bch_fs *c,
 		   struct moving_context *ctxt,
-		   struct write_point *wp,
+		   struct bch_devs_mask *devs,
 		   struct bkey_s_c k,
 		   const struct bch_extent_ptr *move_ptr)
 {
@@ -280,7 +282,7 @@ int bch2_data_move(struct bch_fs *c,
 
 	migrate_bio_init(io, &io->write.op.wbio.bio, k.k->size);
 
-	bch2_migrate_write_init(c, &io->write, wp, k, move_ptr, 0);
+	bch2_migrate_write_init(c, &io->write, devs, k, move_ptr, 0);
 
 	trace_move_read(&io->write.key.k);
 
diff --git a/libbcachefs/move.h b/libbcachefs/move.h
index 71edcf13..a756a462 100644
--- a/libbcachefs/move.h
+++ b/libbcachefs/move.h
@@ -20,12 +20,9 @@ struct migrate_write {
 	struct bch_write_op	op;
 };
 
-void bch2_migrate_write_init(struct bch_fs *,
-			    struct migrate_write *,
-			    struct write_point *,
-			    struct bkey_s_c,
-			    const struct bch_extent_ptr *,
-			    unsigned);
+void bch2_migrate_write_init(struct bch_fs *, struct migrate_write *,
+			     struct bch_devs_mask *, struct bkey_s_c,
+			     const struct bch_extent_ptr *, unsigned);
 
 #define SECTORS_IN_FLIGHT_PER_DEVICE	2048
 
@@ -69,11 +66,9 @@ struct moving_io {
 	struct bio_vec		bi_inline_vecs[0];
 };
 
-int bch2_data_move(struct bch_fs *,
-		  struct moving_context *,
-		  struct write_point *,
-		  struct bkey_s_c,
-		  const struct bch_extent_ptr *);
+int bch2_data_move(struct bch_fs *, struct moving_context *,
+		   struct bch_devs_mask *, struct bkey_s_c,
+		   const struct bch_extent_ptr *);
 
 int bch2_move_ctxt_wait(struct moving_context *);
 void bch2_move_ctxt_wait_for_io(struct moving_context *);
diff --git a/libbcachefs/movinggc.c b/libbcachefs/movinggc.c
index 72cbb9d5..125159ee 100644
--- a/libbcachefs/movinggc.c
+++ b/libbcachefs/movinggc.c
@@ -14,6 +14,7 @@
 #include "keylist.h"
 #include "move.h"
 #include "movinggc.h"
+#include "super-io.h"
 
 #include <trace/events/bcachefs.h>
 #include <linux/freezer.h>
@@ -72,7 +73,7 @@ static int issue_moving_gc_move(struct bch_dev *ca,
 	if (!ptr) /* We raced - bucket's been reused */
 		return 0;
 
-	ret = bch2_data_move(c, ctxt, &ca->copygc_write_point, k, ptr);
+	ret = bch2_data_move(c, ctxt, &ca->self, k, ptr);
 	if (!ret)
 		trace_gc_copy(k.k);
 	else
diff --git a/libbcachefs/super.c b/libbcachefs/super.c
index dfb95d0d..0342778d 100644
--- a/libbcachefs/super.c
+++ b/libbcachefs/super.c
@@ -376,7 +376,7 @@ err:
 static void bch2_fs_free(struct bch_fs *c)
 {
 	bch2_fs_encryption_exit(c);
-	bch2_fs_btree_exit(c);
+	bch2_fs_btree_cache_exit(c);
 	bch2_fs_journal_exit(&c->journal);
 	bch2_io_clock_exit(&c->io_clock[WRITE]);
 	bch2_io_clock_exit(&c->io_clock[READ]);
@@ -491,7 +491,6 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	mutex_init(&c->state_lock);
 	mutex_init(&c->sb_lock);
 	mutex_init(&c->replicas_gc_lock);
-	mutex_init(&c->btree_cache_lock);
 	mutex_init(&c->bucket_lock);
 	mutex_init(&c->btree_root_lock);
 	INIT_WORK(&c->read_only_work, bch2_fs_read_only_work);
@@ -507,9 +506,6 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	bch2_fs_tiering_init(c);
 
 	INIT_LIST_HEAD(&c->list);
-	INIT_LIST_HEAD(&c->btree_cache);
-	INIT_LIST_HEAD(&c->btree_cache_freeable);
-	INIT_LIST_HEAD(&c->btree_cache_freed);
 
 	INIT_LIST_HEAD(&c->btree_interior_update_list);
 	mutex_init(&c->btree_reserve_cache_lock);
@@ -546,6 +542,8 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	c->journal.blocked_time	= &c->journal_blocked_time;
 	c->journal.flush_seq_time = &c->journal_flush_seq_time;
 
+	bch2_fs_btree_cache_init_early(&c->btree_cache);
+
 	mutex_lock(&c->sb_lock);
 
 	if (bch2_sb_to_fs(c, sb)) {
@@ -599,7 +597,7 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	    bch2_io_clock_init(&c->io_clock[READ]) ||
 	    bch2_io_clock_init(&c->io_clock[WRITE]) ||
 	    bch2_fs_journal_init(&c->journal) ||
-	    bch2_fs_btree_init(c) ||
+	    bch2_fs_btree_cache_init(c) ||
 	    bch2_fs_encryption_init(c) ||
 	    bch2_fs_compress_init(c) ||
 	    bch2_check_set_has_compressed_data(c, c->opts.compression))
@@ -1107,8 +1105,6 @@ static int bch2_dev_alloc(struct bch_fs *c, unsigned dev_idx)
 	ca->dev_idx = dev_idx;
 	__set_bit(ca->dev_idx, ca->self.d);
 
-	ca->copygc_write_point.type = BCH_DATA_USER;
-
 	spin_lock_init(&ca->freelist_lock);
 	bch2_dev_moving_gc_init(ca);
 
@@ -1169,8 +1165,6 @@ static int bch2_dev_alloc(struct bch_fs *c, unsigned dev_idx)
 	for (i = 0; i < RESERVE_NR; i++)
 		total_reserve += ca->free[i].size;
 
-	ca->copygc_write_point.group = &ca->self;
-
 	ca->fs = c;
 	rcu_assign_pointer(c->devs[ca->dev_idx], ca);
 
diff --git a/libbcachefs/sysfs.c b/libbcachefs/sysfs.c
index 07d9be75..c20769b7 100644
--- a/libbcachefs/sysfs.c
+++ b/libbcachefs/sysfs.c
@@ -209,11 +209,11 @@ static size_t bch2_btree_cache_size(struct bch_fs *c)
 	size_t ret = 0;
 	struct btree *b;
 
-	mutex_lock(&c->btree_cache_lock);
-	list_for_each_entry(b, &c->btree_cache, list)
+	mutex_lock(&c->btree_cache.lock);
+	list_for_each_entry(b, &c->btree_cache.live, list)
 		ret += btree_bytes(c);
 
-	mutex_unlock(&c->btree_cache_lock);
+	mutex_unlock(&c->btree_cache.lock);
 	return ret;
 }
 
@@ -436,7 +436,7 @@ STORE(__bch2_fs)
 
 		sc.gfp_mask = GFP_KERNEL;
 		sc.nr_to_scan = strtoul_or_return(buf);
-		c->btree_cache_shrink.scan_objects(&c->btree_cache_shrink, &sc);
+		c->btree_cache.shrink.scan_objects(&c->btree_cache.shrink, &sc);
 	}
 
 	return size;
diff --git a/libbcachefs/tier.c b/libbcachefs/tier.c
index b68cae75..cbfcfccc 100644
--- a/libbcachefs/tier.c
+++ b/libbcachefs/tier.c
@@ -54,7 +54,7 @@ static int issue_tiering_move(struct bch_fs *c,
 {
 	int ret;
 
-	ret = bch2_data_move(c, ctxt, &tier->wp, k, NULL);
+	ret = bch2_data_move(c, ctxt, &tier->devs, k, NULL);
 	if (!ret)
 		trace_tiering_copy(k.k);
 	else
@@ -241,6 +241,5 @@ void bch2_fs_tiering_init(struct bch_fs *c)
 	for (i = 0; i < ARRAY_SIZE(c->tiers); i++) {
 		c->tiers[i].idx = i;
 		bch2_pd_controller_init(&c->tiers[i].pd);
-		c->tiers[i].wp.group = &c->tiers[i].devs;
 	}
 }