diff --git a/.bcachefs_revision b/.bcachefs_revision
index d29d45d4..7c242654 100644
--- a/.bcachefs_revision
+++ b/.bcachefs_revision
@@ -1 +1 @@
-90d78c246188f4e90bd9ceb29fe95186b7dc680d
+e7f4678827ad7bf7e294105e7bb3a53e04474070
diff --git a/libbcachefs/acl.c b/libbcachefs/acl.c
index 4016ab96..d29bdafa 100644
--- a/libbcachefs/acl.c
+++ b/libbcachefs/acl.c
@@ -180,27 +180,16 @@ int bch2_set_acl(struct inode *vinode, struct posix_acl *acl, int type)
 {
 	struct bch_inode_info *inode = to_bch_ei(vinode);
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
+	umode_t mode = inode->v.i_mode;
 	int name_index;
 	void *value = NULL;
 	size_t size = 0;
 	int ret;
 
 	if (type == ACL_TYPE_ACCESS && acl) {
-		umode_t mode = inode->v.i_mode;
-
 		ret = posix_acl_update_mode(&inode->v, &mode, &acl);
 		if (ret)
 			return ret;
-
-		mutex_lock(&inode->ei_update_lock);
-		inode->v.i_mode = mode;
-		inode->v.i_ctime = current_time(&inode->v);
-
-		ret = bch2_write_inode(c, inode);
-		mutex_unlock(&inode->ei_update_lock);
-
-		if (ret)
-			return ret;
 	}
 
 	switch (type) {
@@ -210,12 +199,8 @@ int bch2_set_acl(struct inode *vinode, struct posix_acl *acl, int type)
 			ret = posix_acl_equiv_mode(acl, &inode->v.i_mode);
 			if (ret < 0)
 				return ret;
-			else {
-				inode->v.i_ctime = current_time(&inode->v);
-				mark_inode_dirty(&inode->v);
-				if (ret == 0)
-					acl = NULL;
-			}
+			if (ret == 0)
+				acl = NULL;
 		}
 		break;
 
@@ -235,8 +220,20 @@ int bch2_set_acl(struct inode *vinode, struct posix_acl *acl, int type)
 			return (int)PTR_ERR(value);
 	}
 
-	ret = bch2_xattr_set(c, inode, "", value, size, 0, name_index);
+	if (mode != inode->v.i_mode) {
+		mutex_lock(&inode->ei_update_lock);
+		inode->v.i_mode = mode;
+		inode->v.i_ctime = current_time(&inode->v);
 
+		ret = bch2_write_inode(c, inode);
+		mutex_unlock(&inode->ei_update_lock);
+
+		if (ret)
+			goto err;
+	}
+
+	ret = bch2_xattr_set(c, inode, "", value, size, 0, name_index);
+err:
 	kfree(value);
 
 	if (ret == -ERANGE)
diff --git a/libbcachefs/alloc.c b/libbcachefs/alloc.c
index a76f2b7c..470ef207 100644
--- a/libbcachefs/alloc.c
+++ b/libbcachefs/alloc.c
@@ -966,11 +966,24 @@ static int bch2_allocator_thread(void *arg)
 			if (fifo_full(&ca->free_inc))
 				break;
 
+			if (!fifo_empty(&ca->free_inc) &&
+			    !fifo_full(&ca->free[RESERVE_MOVINGGC]))
+				break;
+
+			/*
+			 * copygc may be waiting until either its reserve fills
+			 * up, or we can't make forward progress:
+			 */
+			ca->allocator_blocked = true;
+			closure_wake_up(&c->freelist_wait);
+
 			if (wait_buckets_available(c, ca)) {
 				up_read(&c->gc_lock);
 				return 0;
 			}
 		}
+
+		ca->allocator_blocked = false;
 		up_read(&c->gc_lock);
 
 		sort_free_inc(c, ca);
diff --git a/libbcachefs/bcachefs.h b/libbcachefs/bcachefs.h
index 75f3a006..369d078c 100644
--- a/libbcachefs/bcachefs.h
+++ b/libbcachefs/bcachefs.h
@@ -399,6 +399,7 @@ struct bch_dev {
 	size_t			inc_gen_really_needs_gc;
 	u64			allocator_journal_seq_flush;
 	bool			allocator_invalidating_data;
+	bool			allocator_blocked;
 
 	alloc_heap		alloc_heap;
 
@@ -671,9 +672,6 @@ struct bch_fs {
 	bool			fsck_alloc_err;
 
 	/* FILESYSTEM */
-	wait_queue_head_t	writeback_wait;
-	atomic_t		writeback_pages;
-	unsigned		writeback_pages_max;
 	atomic_long_t		nr_inodes;
 
 	/* QUOTAS */
diff --git a/libbcachefs/bset.c b/libbcachefs/bset.c
index a07d5540..92046ae4 100644
--- a/libbcachefs/bset.c
+++ b/libbcachefs/bset.c
@@ -174,13 +174,11 @@ static void bch2_btree_node_iter_next_check(struct btree_node_iter *iter,
 void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
 				struct btree *b)
 {
-	struct btree_node_iter_set *set;
+	struct btree_node_iter_set *set, *prev = NULL;
 	struct bset_tree *t;
 	struct bkey_packed *k, *first;
 
-	BUG_ON(iter->used > MAX_BSETS);
-
-	if (!iter->used)
+	if (bch2_btree_node_iter_end(iter))
 		return;
 
 	btree_node_iter_for_each(iter, set) {
@@ -190,8 +188,10 @@ void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
 		BUG_ON(__btree_node_offset_to_key(b, set->end) !=
 		       btree_bkey_last(b, t));
 
-		BUG_ON(set + 1 < iter->data + iter->used &&
-		       btree_node_iter_cmp(iter, b, set[0], set[1]) > 0);
+		BUG_ON(prev &&
+		       btree_node_iter_cmp(iter, b, *prev, *set) > 0);
+
+		prev = set;
 	}
 
 	first = __btree_node_offset_to_key(b, iter->data[0].k);
@@ -1463,22 +1463,8 @@ void bch2_btree_node_iter_push(struct btree_node_iter *iter,
 			       const struct bkey_packed *k,
 			       const struct bkey_packed *end)
 {
-	if (k != end) {
-		struct btree_node_iter_set *pos, n =
-			((struct btree_node_iter_set) {
-				 __btree_node_key_to_offset(b, k),
-				 __btree_node_key_to_offset(b, end)
-			 });
-
-		btree_node_iter_for_each(iter, pos)
-			if (btree_node_iter_cmp(iter, b, n, *pos) <= 0)
-				break;
-
-		memmove(pos + 1, pos,
-			(void *) (iter->data + iter->used) - (void *) pos);
-		iter->used++;
-		*pos = n;
-	}
+	__bch2_btree_node_iter_push(iter, b, k, end);
+	bch2_btree_node_iter_sort(iter, b);
 }
 
 noinline __flatten __attribute__((cold))
@@ -1595,8 +1581,6 @@ struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *iter,
 {
 	struct btree_node_iter_set *set;
 
-	EBUG_ON(iter->used > MAX_BSETS);
-
 	btree_node_iter_for_each(iter, set)
 		if (set->end == t->end_offset)
 			return __btree_node_offset_to_key(b, set->k);
@@ -1604,47 +1588,67 @@ struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *iter,
 	return btree_bkey_last(b, t);
 }
 
-static inline void btree_node_iter_sift(struct btree_node_iter *iter,
-					struct btree *b,
-					unsigned start)
-{
-	unsigned i;
-
-	EBUG_ON(iter->used > MAX_BSETS);
-
-	for (i = start;
-	     i + 1 < iter->used &&
-	     btree_node_iter_cmp(iter, b, iter->data[i], iter->data[i + 1]) > 0;
-	     i++)
-		swap(iter->data[i], iter->data[i + 1]);
-}
-
-static inline void btree_node_iter_sort_two(struct btree_node_iter *iter,
+static inline bool btree_node_iter_sort_two(struct btree_node_iter *iter,
 					    struct btree *b,
 					    unsigned first)
 {
-	if (btree_node_iter_cmp(iter, b,
-				iter->data[first],
-				iter->data[first + 1]) > 0)
+	bool ret;
+
+	if ((ret = (btree_node_iter_cmp(iter, b,
+					iter->data[first],
+					iter->data[first + 1]) > 0)))
 		swap(iter->data[first], iter->data[first + 1]);
+	return ret;
 }
 
 void bch2_btree_node_iter_sort(struct btree_node_iter *iter,
 			       struct btree *b)
 {
-	EBUG_ON(iter->used > 3);
-
 	/* unrolled bubble sort: */
 
-	if (iter->used > 2) {
+	if (!__btree_node_iter_set_end(iter, 2)) {
 		btree_node_iter_sort_two(iter, b, 0);
 		btree_node_iter_sort_two(iter, b, 1);
 	}
 
-	if (iter->used > 1)
+	if (!__btree_node_iter_set_end(iter, 1))
 		btree_node_iter_sort_two(iter, b, 0);
 }
 
+void bch2_btree_node_iter_set_drop(struct btree_node_iter *iter,
+				   struct btree_node_iter_set *set)
+{
+	struct btree_node_iter_set *last =
+		iter->data + ARRAY_SIZE(iter->data) - 1;
+
+	memmove(&set[0], &set[1], (void *) last - (void *) set);
+	*last = (struct btree_node_iter_set) { 0, 0 };
+}
+
+static inline void __bch2_btree_node_iter_advance(struct btree_node_iter *iter,
+						  struct btree *b)
+{
+	iter->data->k += __bch2_btree_node_iter_peek_all(iter, b)->u64s;
+
+	EBUG_ON(iter->data->k > iter->data->end);
+
+	if (unlikely(__btree_node_iter_set_end(iter, 0))) {
+		bch2_btree_node_iter_set_drop(iter, iter->data);
+		return;
+	}
+
+	if (__btree_node_iter_set_end(iter, 1))
+		return;
+
+	if (!btree_node_iter_sort_two(iter, b, 0))
+		return;
+
+	if (__btree_node_iter_set_end(iter, 2))
+		return;
+
+	btree_node_iter_sort_two(iter, b, 1);
+}
+
 /**
  * bch_btree_node_iter_advance - advance @iter by one key
  *
@@ -1656,23 +1660,24 @@ void bch2_btree_node_iter_advance(struct btree_node_iter *iter,
 {
 #ifdef CONFIG_BCACHEFS_DEBUG
 	struct bkey_packed *k = bch2_btree_node_iter_peek_all(iter, b);
-#endif
-	iter->data->k += __bch2_btree_node_iter_peek_all(iter, b)->u64s;
 
-	EBUG_ON(iter->data->k > iter->data->end);
-
-	if (iter->data->k == iter->data->end) {
-		EBUG_ON(iter->used == 0);
-		iter->data[0] = iter->data[--iter->used];
-	}
-
-	btree_node_iter_sift(iter, b, 0);
-
-#ifdef CONFIG_BCACHEFS_DEBUG
+	__bch2_btree_node_iter_advance(iter, b);
 	bch2_btree_node_iter_next_check(iter, b, k);
+#else
+	__bch2_btree_node_iter_advance(iter, b);
 #endif
 }
 
+static inline bool __btree_node_iter_used(struct btree_node_iter *iter)
+{
+	unsigned n = ARRAY_SIZE(iter->data);
+
+	while (n && __btree_node_iter_set_end(iter, n - 1))
+		--n;
+
+	return n;
+}
+
 /*
  * Expensive:
  */
@@ -1683,7 +1688,7 @@ struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *iter,
 	struct btree_node_iter_set *set;
 	struct bset_tree *t;
 	struct bset_tree *prev_t;
-	unsigned end;
+	unsigned end, used;
 
 	bch2_btree_node_iter_verify(iter, b);
 
@@ -1715,10 +1720,12 @@ struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *iter,
 			goto out;
 		}
 
+	used = __btree_node_iter_used(iter);
+	BUG_ON(used >= ARRAY_SIZE(iter->data));
+
 	memmove(&iter->data[1],
 		&iter->data[0],
-		(void *) &iter->data[iter->used] - (void *) &iter->data[0]);
-	iter->used++;
+		(void *) &iter->data[used] - (void *) &iter->data[0]);
 out:
 	iter->data[0].k = __btree_node_key_to_offset(b, prev);
 	iter->data[0].end = end;
diff --git a/libbcachefs/bset.h b/libbcachefs/bset.h
index f5a84481..cc4ea5d8 100644
--- a/libbcachefs/bset.h
+++ b/libbcachefs/bset.h
@@ -422,7 +422,6 @@ static inline enum bch_extent_overlap bch2_extent_overlap(const struct bkey *k,
 
 struct btree_node_iter {
 	u8		is_extents;
-	u16		used;
 
 	struct btree_node_iter_set {
 		u16	k, end;
@@ -432,8 +431,8 @@ struct btree_node_iter {
 static inline void __bch2_btree_node_iter_init(struct btree_node_iter *iter,
 					      bool is_extents)
 {
-	iter->used = 0;
 	iter->is_extents = is_extents;
+	memset(iter->data, 0, sizeof(iter->data));
 }
 
 void bch2_btree_node_iter_push(struct btree_node_iter *, struct btree *,
@@ -448,16 +447,25 @@ struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *,
 						 struct bset_tree *);
 
 void bch2_btree_node_iter_sort(struct btree_node_iter *, struct btree *);
+void bch2_btree_node_iter_set_drop(struct btree_node_iter *,
+				   struct btree_node_iter_set *);
 void bch2_btree_node_iter_advance(struct btree_node_iter *, struct btree *);
 
-#define btree_node_iter_for_each(_iter, _set)			\
-	for (_set = (_iter)->data;				\
-	     _set < (_iter)->data + (_iter)->used;		\
+#define btree_node_iter_for_each(_iter, _set)				\
+	for (_set = (_iter)->data;					\
+	     _set < (_iter)->data + ARRAY_SIZE((_iter)->data) &&	\
+	     (_set)->k != (_set)->end;					\
 	     _set++)
 
+static inline bool __btree_node_iter_set_end(struct btree_node_iter *iter,
+					     unsigned i)
+{
+	return iter->data[i].k == iter->data[i].end;
+}
+
 static inline bool bch2_btree_node_iter_end(struct btree_node_iter *iter)
 {
-	return !iter->used;
+	return __btree_node_iter_set_end(iter, 0);
 }
 
 static inline int __btree_node_iter_cmp(bool is_extents,
@@ -493,11 +501,18 @@ static inline void __bch2_btree_node_iter_push(struct btree_node_iter *iter,
 			      const struct bkey_packed *k,
 			      const struct bkey_packed *end)
 {
-	if (k != end)
-		iter->data[iter->used++] = (struct btree_node_iter_set) {
+	if (k != end) {
+		struct btree_node_iter_set *pos;
+
+		btree_node_iter_for_each(iter, pos)
+			;
+
+		BUG_ON(pos >= iter->data + ARRAY_SIZE(iter->data));
+		*pos = (struct btree_node_iter_set) {
 			__btree_node_key_to_offset(b, k),
 			__btree_node_key_to_offset(b, end)
 		};
+	}
 }
 
 static inline struct bkey_packed *
diff --git a/libbcachefs/btree_io.c b/libbcachefs/btree_io.c
index d805fb41..881039b1 100644
--- a/libbcachefs/btree_io.c
+++ b/libbcachefs/btree_io.c
@@ -18,6 +18,43 @@
 
 #include <trace/events/bcachefs.h>
 
+/* btree_node_iter_large: */
+
+#define btree_node_iter_cmp_heap(h, _l, _r)				\
+	__btree_node_iter_cmp((iter)->is_extents, b,			\
+			       __btree_node_offset_to_key(b, (_l).k),	\
+			       __btree_node_offset_to_key(b, (_r).k))
+
+void bch2_btree_node_iter_large_push(struct btree_node_iter_large *iter,
+				     struct btree *b,
+				     const struct bkey_packed *k,
+				     const struct bkey_packed *end)
+{
+	if (k != end) {
+		struct btree_node_iter_set n =
+			((struct btree_node_iter_set) {
+				 __btree_node_key_to_offset(b, k),
+				 __btree_node_key_to_offset(b, end)
+			 });
+
+		__heap_add(iter, n, btree_node_iter_cmp_heap);
+	}
+}
+
+void bch2_btree_node_iter_large_advance(struct btree_node_iter_large *iter,
+					struct btree *b)
+{
+	iter->data->k += __btree_node_offset_to_key(b, iter->data->k)->u64s;
+
+	EBUG_ON(!iter->used);
+	EBUG_ON(iter->data->k > iter->data->end);
+
+	if (iter->data->k == iter->data->end)
+		heap_del(iter, 0, btree_node_iter_cmp_heap);
+	else
+		heap_sift_down(iter, 0, btree_node_iter_cmp_heap);
+}
+
 static void verify_no_dups(struct btree *b,
 			   struct bkey_packed *start,
 			   struct bkey_packed *end)
@@ -910,7 +947,7 @@ enum btree_validate_ret {
 
 #define btree_err(type, c, b, i, msg, ...)				\
 ({									\
-	char buf[200], *out = buf, *end = out + sizeof(buf);		\
+	char _buf[200], *out = _buf, *end = out + sizeof(_buf);		\
 									\
 	out += btree_err_msg(c, b, i, b->written, write, out, end - out);\
 	out += scnprintf(out, end - out, ": " msg, ##__VA_ARGS__);	\
@@ -918,9 +955,9 @@ enum btree_validate_ret {
 	if (type == BTREE_ERR_FIXABLE &&				\
 	    write == READ &&						\
 	    !test_bit(BCH_FS_INITIAL_GC_DONE, &c->flags)) {		\
-		mustfix_fsck_err(c, "%s", buf);				\
+		mustfix_fsck_err(c, "%s", _buf);			\
 	} else {							\
-		bch_err(c, "%s", buf);					\
+		bch_err(c, "%s", _buf);					\
 									\
 		switch (type) {						\
 		case BTREE_ERR_FIXABLE:					\
@@ -1108,7 +1145,7 @@ fsck_err:
 int bch2_btree_node_read_done(struct bch_fs *c, struct btree *b, bool have_retry)
 {
 	struct btree_node_entry *bne;
-	struct btree_node_iter *iter;
+	struct btree_node_iter_large *iter;
 	struct btree_node *sorted;
 	struct bkey_packed *k;
 	struct bset *i;
@@ -1117,7 +1154,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct btree *b, bool have_retry
 	int ret, retry_read = 0, write = READ;
 
 	iter = mempool_alloc(&c->fill_iter, GFP_NOIO);
-	__bch2_btree_node_iter_init(iter, btree_node_is_extents(b));
+	__bch2_btree_node_iter_large_init(iter, btree_node_is_extents(b));
 
 	if (bch2_meta_read_fault("btree"))
 		btree_err(BTREE_ERR_MUST_RETRY, c, b, NULL,
@@ -1202,11 +1239,11 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct btree *b, bool have_retry
 				continue;
 		}
 
-		__bch2_btree_node_iter_push(iter, b,
+		bch2_btree_node_iter_large_push(iter, b,
 					   i->start,
 					   vstruct_idx(i, whiteout_u64s));
 
-		__bch2_btree_node_iter_push(iter, b,
+		bch2_btree_node_iter_large_push(iter, b,
 					   vstruct_idx(i, whiteout_u64s),
 					   vstruct_last(i));
 	}
diff --git a/libbcachefs/btree_io.h b/libbcachefs/btree_io.h
index f2790716..01df817d 100644
--- a/libbcachefs/btree_io.h
+++ b/libbcachefs/btree_io.h
@@ -1,6 +1,7 @@
 #ifndef _BCACHEFS_BTREE_IO_H
 #define _BCACHEFS_BTREE_IO_H
 
+#include "bset.h"
 #include "extents.h"
 #include "io_types.h"
 
@@ -141,4 +142,55 @@ void bch2_btree_flush_all_writes(struct bch_fs *);
 void bch2_btree_verify_flushed(struct bch_fs *);
 ssize_t bch2_dirty_btree_nodes_print(struct bch_fs *, char *);
 
+/* Sorting */
+
+struct btree_node_iter_large {
+	u8		is_extents;
+	u16		used;
+
+	struct btree_node_iter_set data[MAX_BSETS];
+};
+
+static inline void
+__bch2_btree_node_iter_large_init(struct btree_node_iter_large *iter,
+				  bool is_extents)
+{
+	iter->used = 0;
+	iter->is_extents = is_extents;
+}
+
+void bch2_btree_node_iter_large_advance(struct btree_node_iter_large *,
+					struct btree *);
+
+void bch2_btree_node_iter_large_push(struct btree_node_iter_large *,
+				     struct btree *,
+				     const struct bkey_packed *,
+				     const struct bkey_packed *);
+
+static inline bool bch2_btree_node_iter_large_end(struct btree_node_iter_large *iter)
+{
+	return !iter->used;
+}
+
+static inline struct bkey_packed *
+bch2_btree_node_iter_large_peek_all(struct btree_node_iter_large *iter,
+				    struct btree *b)
+{
+	return bch2_btree_node_iter_large_end(iter)
+		? NULL
+		: __btree_node_offset_to_key(b, iter->data->k);
+}
+
+static inline struct bkey_packed *
+bch2_btree_node_iter_large_next_all(struct btree_node_iter_large *iter,
+				    struct btree *b)
+{
+	struct bkey_packed *ret = bch2_btree_node_iter_large_peek_all(iter, b);
+
+	if (ret)
+		bch2_btree_node_iter_large_advance(iter, b);
+
+	return ret;
+}
+
 #endif /* _BCACHEFS_BTREE_IO_H */
diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index 21a6cbc2..cc5bcbb2 100644
--- a/libbcachefs/btree_iter.c
+++ b/libbcachefs/btree_iter.c
@@ -382,7 +382,7 @@ found:
 	} else if (set->k < offset + clobber_u64s) {
 		set->k = offset + new_u64s;
 		if (set->k == set->end)
-			*set = node_iter->data[--node_iter->used];
+			bch2_btree_node_iter_set_drop(node_iter, set);
 	} else {
 		set->k = (int) set->k + shift;
 		goto iter_current_key_not_modified;
diff --git a/libbcachefs/extents.c b/libbcachefs/extents.c
index 37470f86..b7d969b1 100644
--- a/libbcachefs/extents.c
+++ b/libbcachefs/extents.c
@@ -28,7 +28,7 @@
 static enum merge_result bch2_extent_merge(struct bch_fs *, struct btree *,
 					   struct bkey_i *, struct bkey_i *);
 
-static void sort_key_next(struct btree_node_iter *iter,
+static void sort_key_next(struct btree_node_iter_large *iter,
 			  struct btree *b,
 			  struct btree_node_iter_set *i)
 {
@@ -54,7 +54,7 @@ static void sort_key_next(struct btree_node_iter *iter,
 	?: (l).k - (r).k;						\
 })
 
-static inline bool should_drop_next_key(struct btree_node_iter *iter,
+static inline bool should_drop_next_key(struct btree_node_iter_large *iter,
 					struct btree *b)
 {
 	struct btree_node_iter_set *l = iter->data, *r = iter->data + 1;
@@ -81,8 +81,8 @@ static inline bool should_drop_next_key(struct btree_node_iter *iter,
 }
 
 struct btree_nr_keys bch2_key_sort_fix_overlapping(struct bset *dst,
-						  struct btree *b,
-						  struct btree_node_iter *iter)
+					struct btree *b,
+					struct btree_node_iter_large *iter)
 {
 	struct bkey_packed *out = dst->start;
 	struct btree_nr_keys nr;
@@ -91,7 +91,7 @@ struct btree_nr_keys bch2_key_sort_fix_overlapping(struct bset *dst,
 
 	heap_resort(iter, key_sort_cmp);
 
-	while (!bch2_btree_node_iter_end(iter)) {
+	while (!bch2_btree_node_iter_large_end(iter)) {
 		if (!should_drop_next_key(iter, b)) {
 			struct bkey_packed *k =
 				__btree_node_offset_to_key(b, iter->data->k);
@@ -148,7 +148,7 @@ bch2_extent_has_group(struct bch_fs *c, struct bkey_s_c_extent e, unsigned group
 		struct bch_dev *ca = c->devs[ptr->dev];
 
 		if (ca->mi.group &&
-		    ca->mi.group == group)
+		    ca->mi.group - 1 == group)
 			return ptr;
 	}
 
@@ -890,13 +890,13 @@ static void extent_save(struct btree *b, struct btree_node_iter *iter,
 		 bkey_start_pos(&_ur)) ?: (r).k - (l).k;		\
 })
 
-static inline void extent_sort_sift(struct btree_node_iter *iter,
+static inline void extent_sort_sift(struct btree_node_iter_large *iter,
 				    struct btree *b, size_t i)
 {
 	heap_sift_down(iter, i, extent_sort_cmp);
 }
 
-static inline void extent_sort_next(struct btree_node_iter *iter,
+static inline void extent_sort_next(struct btree_node_iter_large *iter,
 				    struct btree *b,
 				    struct btree_node_iter_set *i)
 {
@@ -938,7 +938,7 @@ static void extent_sort_append(struct bch_fs *c,
 struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 					struct bset *dst,
 					struct btree *b,
-					struct btree_node_iter *iter)
+					struct btree_node_iter_large *iter)
 {
 	struct bkey_format *f = &b->format;
 	struct btree_node_iter_set *_l = iter->data, *_r;
@@ -951,7 +951,7 @@ struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 
 	heap_resort(iter, extent_sort_cmp);
 
-	while (!bch2_btree_node_iter_end(iter)) {
+	while (!bch2_btree_node_iter_large_end(iter)) {
 		lk = __btree_node_offset_to_key(b, _l->k);
 
 		if (iter->used == 1) {
diff --git a/libbcachefs/extents.h b/libbcachefs/extents.h
index 83c0f24d..1ce0d38d 100644
--- a/libbcachefs/extents.h
+++ b/libbcachefs/extents.h
@@ -8,6 +8,7 @@
 struct bch_fs;
 struct journal_res;
 struct btree_node_iter;
+struct btree_node_iter_large;
 struct btree_insert;
 struct btree_insert_entry;
 struct extent_insert_hook;
@@ -16,11 +17,11 @@ union bch_extent_crc;
 
 struct btree_nr_keys bch2_key_sort_fix_overlapping(struct bset *,
 						  struct btree *,
-						  struct btree_node_iter *);
+						  struct btree_node_iter_large *);
 struct btree_nr_keys bch2_extent_sort_fix_overlapping(struct bch_fs *c,
 						     struct bset *,
 						     struct btree *,
-						     struct btree_node_iter *);
+						     struct btree_node_iter_large *);
 
 extern const struct bkey_ops bch2_bkey_btree_ops;
 extern const struct bkey_ops bch2_bkey_extent_ops;
diff --git a/libbcachefs/fs-io.c b/libbcachefs/fs-io.c
index 46cffc5c..cb90738c 100644
--- a/libbcachefs/fs-io.c
+++ b/libbcachefs/fs-io.c
@@ -1193,9 +1193,6 @@ static void bch2_writepage_io_done(struct closure *cl)
 	struct bio_vec *bvec;
 	unsigned i;
 
-	atomic_sub(bio->bi_vcnt, &c->writeback_pages);
-	wake_up(&c->writeback_wait);
-
 	if (io->op.op.error) {
 		bio_for_each_segment_all(bvec, bio, i)
 			SetPageError(bvec->bv_page);
@@ -1232,11 +1229,8 @@ static void bch2_writepage_io_done(struct closure *cl)
 static void bch2_writepage_do_io(struct bch_writepage_state *w)
 {
 	struct bch_writepage_io *io = w->io;
-	struct bio *bio = &io->op.op.wbio.bio;
 
 	w->io = NULL;
-	atomic_add(bio->bi_vcnt, &io->op.op.c->writeback_pages);
-
 	closure_call(&io->op.op.cl, bch2_write, NULL, &io->cl);
 	continue_at(&io->cl, bch2_writepage_io_done, NULL);
 }
@@ -1270,11 +1264,13 @@ static void bch2_writepage_io_alloc(struct bch_fs *c,
 	op->wbio.bio.bi_iter.bi_sector = offset;
 }
 
-static int __bch2_writepage(struct bch_fs *c, struct page *page,
+static int __bch2_writepage(struct page *page,
 			    struct writeback_control *wbc,
-			    struct bch_writepage_state *w)
+			    void *data)
 {
 	struct bch_inode_info *inode = to_bch_ei(page->mapping->host);
+	struct bch_fs *c = inode->v.i_sb->s_fs_info;
+	struct bch_writepage_state *w = data;
 	struct bch_page_state new, old;
 	unsigned offset;
 	loff_t i_size = i_size_read(&inode->v);
@@ -1318,6 +1314,10 @@ do_io:
 		new.dirty_sectors = 0;
 	});
 
+	BUG_ON(PageWriteback(page));
+	set_page_writeback(page);
+	unlock_page(page);
+
 	if (w->io &&
 	    (w->io->op.op.res.nr_replicas != new.nr_replicas ||
 	     !bio_can_add_page_contig(&w->io->op.op.wbio.bio, page)))
@@ -1334,16 +1334,11 @@ do_io:
 	if (old.reserved)
 		w->io->op.op.res.sectors += old.reservation_replicas * PAGE_SECTORS;
 
-	/* while page is locked: */
 	w->io->op.new_i_size = i_size;
 
 	if (wbc->sync_mode == WB_SYNC_ALL)
 		w->io->op.op.wbio.bio.bi_opf |= REQ_SYNC;
 
-	BUG_ON(PageWriteback(page));
-	set_page_writeback(page);
-	unlock_page(page);
-
 	return 0;
 }
 
@@ -1352,147 +1347,14 @@ int bch2_writepages(struct address_space *mapping, struct writeback_control *wbc
 	struct bch_fs *c = mapping->host->i_sb->s_fs_info;
 	struct bch_writepage_state w =
 		bch_writepage_state_init(c, to_bch_ei(mapping->host));
-	struct pagecache_iter iter;
-	struct page *page;
-	int ret = 0;
-	int done = 0;
-	pgoff_t uninitialized_var(writeback_index);
-	pgoff_t index;
-	pgoff_t end;		/* Inclusive */
-	pgoff_t done_index;
-	int cycled;
-	int range_whole = 0;
-	int tag;
-
-	if (wbc->range_cyclic) {
-		writeback_index = mapping->writeback_index; /* prev offset */
-		index = writeback_index;
-		if (index == 0)
-			cycled = 1;
-		else
-			cycled = 0;
-		end = -1;
-	} else {
-		index = wbc->range_start >> PAGE_SHIFT;
-		end = wbc->range_end >> PAGE_SHIFT;
-		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
-			range_whole = 1;
-		cycled = 1; /* ignore range_cyclic tests */
-	}
-	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
-		tag = PAGECACHE_TAG_TOWRITE;
-	else
-		tag = PAGECACHE_TAG_DIRTY;
-retry:
-	if (wbc->sync_mode == WB_SYNC_ALL || wbc->tagged_writepages)
-		tag_pages_for_writeback(mapping, index, end);
-
-	done_index = index;
-get_pages:
-	for_each_pagecache_tag(&iter, mapping, tag, index, end, page) {
-		done_index = page->index;
-
-		if (w.io &&
-		    !bio_can_add_page_contig(&w.io->op.op.wbio.bio, page))
-			bch2_writepage_do_io(&w);
-
-		if (!w.io &&
-		    atomic_read(&c->writeback_pages) >=
-		    c->writeback_pages_max) {
-			/* don't sleep with pages pinned: */
-			pagecache_iter_release(&iter);
-
-			__wait_event(c->writeback_wait,
-				     atomic_read(&c->writeback_pages) <
-				     c->writeback_pages_max);
-			goto get_pages;
-		}
-
-		lock_page(page);
-
-		/*
-		 * Page truncated or invalidated. We can freely skip it
-		 * then, even for data integrity operations: the page
-		 * has disappeared concurrently, so there could be no
-		 * real expectation of this data interity operation
-		 * even if there is now a new, dirty page at the same
-		 * pagecache address.
-		 */
-		if (unlikely(page->mapping != mapping)) {
-continue_unlock:
-			unlock_page(page);
-			continue;
-		}
-
-		if (!PageDirty(page)) {
-			/* someone wrote it for us */
-			goto continue_unlock;
-		}
-
-		if (PageWriteback(page)) {
-			if (wbc->sync_mode != WB_SYNC_NONE)
-				wait_on_page_writeback(page);
-			else
-				goto continue_unlock;
-		}
-
-		BUG_ON(PageWriteback(page));
-		if (!clear_page_dirty_for_io(page))
-			goto continue_unlock;
-
-		trace_wbc_writepage(wbc, inode_to_bdi(mapping->host));
-		ret = __bch2_writepage(c, page, wbc, &w);
-		if (unlikely(ret)) {
-			if (ret == AOP_WRITEPAGE_ACTIVATE) {
-				unlock_page(page);
-				ret = 0;
-			} else {
-				/*
-				 * done_index is set past this page,
-				 * so media errors will not choke
-				 * background writeout for the entire
-				 * file. This has consequences for
-				 * range_cyclic semantics (ie. it may
-				 * not be suitable for data integrity
-				 * writeout).
-				 */
-				done_index = page->index + 1;
-				done = 1;
-				break;
-			}
-		}
-
-		/*
-		 * We stop writing back only if we are not doing
-		 * integrity sync. In case of integrity sync we have to
-		 * keep going until we have written all the pages
-		 * we tagged for writeback prior to entering this loop.
-		 */
-		if (--wbc->nr_to_write <= 0 &&
-		    wbc->sync_mode == WB_SYNC_NONE) {
-			done = 1;
-			break;
-		}
-	}
-	pagecache_iter_release(&iter);
+	struct blk_plug plug;
+	int ret;
 
+	blk_start_plug(&plug);
+	ret = write_cache_pages(mapping, wbc, __bch2_writepage, &w);
 	if (w.io)
 		bch2_writepage_do_io(&w);
-
-	if (!cycled && !done) {
-		/*
-		 * range_cyclic:
-		 * We hit the last page and there is more work to be done: wrap
-		 * back to the start of the file
-		 */
-		cycled = 1;
-		index = 0;
-		end = writeback_index - 1;
-		goto retry;
-	}
-	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
-		mapping->writeback_index = done_index;
-
+	blk_finish_plug(&plug);
 	return ret;
 }
 
@@ -1503,7 +1365,7 @@ int bch2_writepage(struct page *page, struct writeback_control *wbc)
 		bch_writepage_state_init(c, to_bch_ei(page->mapping->host));
 	int ret;
 
-	ret = __bch2_writepage(c, page, wbc, &w);
+	ret = __bch2_writepage(page, wbc, &w);
 	if (w.io)
 		bch2_writepage_do_io(&w);
 
diff --git a/libbcachefs/journal.c b/libbcachefs/journal.c
index 8ce17452..ea8a6282 100644
--- a/libbcachefs/journal.c
+++ b/libbcachefs/journal.c
@@ -2964,7 +2964,7 @@ int bch2_fs_journal_init(struct journal *j)
 
 	j->buf[0].size		= JOURNAL_ENTRY_SIZE_MIN;
 	j->buf[1].size		= JOURNAL_ENTRY_SIZE_MIN;
-	j->write_delay_ms	= 100;
+	j->write_delay_ms	= 1000;
 	j->reclaim_delay_ms	= 100;
 
 	bkey_extent_init(&j->key);
diff --git a/libbcachefs/movinggc.c b/libbcachefs/movinggc.c
index ad56e039..2aa58b55 100644
--- a/libbcachefs/movinggc.c
+++ b/libbcachefs/movinggc.c
@@ -106,8 +106,8 @@ static bool have_copygc_reserve(struct bch_dev *ca)
 	bool ret;
 
 	spin_lock(&ca->freelist_lock);
-	ret = fifo_used(&ca->free[RESERVE_MOVINGGC]) >=
-		COPYGC_BUCKETS_PER_ITER(ca);
+	ret = fifo_full(&ca->free[RESERVE_MOVINGGC]) ||
+		ca->allocator_blocked;
 	spin_unlock(&ca->freelist_lock);
 
 	return ret;
diff --git a/libbcachefs/super-io.h b/libbcachefs/super-io.h
index 3811de72..2fa0719f 100644
--- a/libbcachefs/super-io.h
+++ b/libbcachefs/super-io.h
@@ -243,7 +243,7 @@ static inline bool dev_in_target(struct bch_dev *ca, unsigned target)
 	case TARGET_DEV:
 		return ca->dev_idx == t.dev;
 	case TARGET_GROUP:
-		return ca->mi.group && ca->mi.group == t.group;
+		return ca->mi.group && ca->mi.group - 1 == t.group;
 	default:
 		BUG();
 	}
diff --git a/libbcachefs/super.c b/libbcachefs/super.c
index abb97128..77670ea6 100644
--- a/libbcachefs/super.c
+++ b/libbcachefs/super.c
@@ -551,9 +551,6 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 
 	seqcount_init(&c->gc_pos_lock);
 
-	init_waitqueue_head(&c->writeback_wait);
-	c->writeback_pages_max = (256 << 10) / PAGE_SIZE;
-
 	c->copy_gc_enabled = 1;
 	c->rebalance_enabled = 1;
 	c->rebalance_percent = 10;
@@ -589,7 +586,8 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 	if (bch2_fs_init_fault("fs_alloc"))
 		goto err;
 
-	iter_size = (btree_blocks(c) + 1) * 2 *
+	iter_size = sizeof(struct btree_node_iter_large) +
+		(btree_blocks(c) + 1) * 2 *
 		sizeof(struct btree_node_iter_set);
 
 	if (!(c->wq = alloc_workqueue("bcachefs",
diff --git a/libbcachefs/sysfs.c b/libbcachefs/sysfs.c
index e42bc1da..601e2707 100644
--- a/libbcachefs/sysfs.c
+++ b/libbcachefs/sysfs.c
@@ -164,8 +164,6 @@ read_attribute(extent_migrate_raced);
 rw_attribute(journal_write_delay_ms);
 rw_attribute(journal_reclaim_delay_ms);
 
-rw_attribute(writeback_pages_max);
-
 rw_attribute(discard);
 rw_attribute(cache_replacement_policy);
 rw_attribute(group);
@@ -311,8 +309,6 @@ SHOW(bch2_fs)
 	sysfs_print(journal_write_delay_ms,	c->journal.write_delay_ms);
 	sysfs_print(journal_reclaim_delay_ms,	c->journal.reclaim_delay_ms);
 
-	sysfs_print(writeback_pages_max,	c->writeback_pages_max);
-
 	sysfs_print(block_size,			block_bytes(c));
 	sysfs_print(btree_node_size,		btree_bytes(c));
 	sysfs_hprint(btree_cache_size,		bch2_btree_cache_size(c));
@@ -373,9 +369,6 @@ STORE(__bch2_fs)
 	sysfs_strtoul(journal_write_delay_ms, c->journal.write_delay_ms);
 	sysfs_strtoul(journal_reclaim_delay_ms, c->journal.reclaim_delay_ms);
 
-	if (attr == &sysfs_writeback_pages_max)
-		c->writeback_pages_max = strtoul_restrict_or_return(buf, 1, UINT_MAX);
-
 	if (attr == &sysfs_btree_gc_periodic) {
 		ssize_t ret = strtoul_safe(buf, c->btree_gc_periodic)
 			?: (ssize_t) size;
@@ -465,8 +458,6 @@ struct attribute *bch2_fs_files[] = {
 	&sysfs_journal_write_delay_ms,
 	&sysfs_journal_reclaim_delay_ms,
 
-	&sysfs_writeback_pages_max,
-
 	&sysfs_rebalance_percent,
 
 	&sysfs_compression_stats,
@@ -913,7 +904,15 @@ STORE(bch2_dev)
 	}
 
 	if (attr == &sysfs_group) {
-		int ret = bch2_dev_group_set(c, ca, buf);
+		char *tmp;
+		int ret;
+
+		tmp = kstrdup(buf, GFP_KERNEL);
+		if (!tmp)
+			return -ENOMEM;
+
+		ret = bch2_dev_group_set(c, ca, strim(tmp));
+		kfree(tmp);
 		if (ret)
 			return ret;
 	}
diff --git a/libbcachefs/util.h b/libbcachefs/util.h
index d475f986..cc89da1f 100644
--- a/libbcachefs/util.h
+++ b/libbcachefs/util.h
@@ -181,15 +181,19 @@ do {									\
 	}								\
 } while (0)
 
-#define heap_add(h, new, cmp)						\
+#define __heap_add(h, d, cmp)						\
+do {									\
+	size_t _i = (h)->used++;					\
+	(h)->data[_i] = d;						\
+									\
+	heap_sift_up(h, _i, cmp);					\
+} while (0)
+
+#define heap_add(h, d, cmp)						\
 ({									\
 	bool _r = !heap_full(h);					\
-	if (_r) {							\
-		size_t _i = (h)->used++;				\
-		(h)->data[_i] = new;					\
-									\
-		heap_sift_up(h, _i, cmp);				\
-	}								\
+	if (_r)								\
+		__heap_add(h, d, cmp);					\
 	_r;								\
 })