diff --git a/.bcachefs_revision b/.bcachefs_revision
index e40e21f8..51df9f0e 100644
--- a/.bcachefs_revision
+++ b/.bcachefs_revision
@@ -1 +1 @@
-f65603966f7474213e6bf22b046e374d01fd6639
+9abf628c701ad92670d697624f674cc01d42705e
diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h
new file mode 100644
index 00000000..c233e3ce
--- /dev/null
+++ b/include/linux/percpu-rwsem.h
@@ -0,0 +1,72 @@
+
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_PERCPU_RWSEM_H
+#define _LINUX_PERCPU_RWSEM_H
+
+#include <pthread.h>
+#include <linux/preempt.h>
+
+struct percpu_rw_semaphore {
+	pthread_rwlock_t	lock;
+};
+
+#define DEFINE_STATIC_PERCPU_RWSEM(name)				\
+static DEFINE_PER_CPU(unsigned int, __percpu_rwsem_rc_##name);		\
+static struct percpu_rw_semaphore name = {				\
+	.rss = __RCU_SYNC_INITIALIZER(name.rss, RCU_SCHED_SYNC),	\
+	.read_count = &__percpu_rwsem_rc_##name,			\
+	.rw_sem = __RWSEM_INITIALIZER(name.rw_sem),			\
+	.writer = __RCUWAIT_INITIALIZER(name.writer),			\
+}
+
+extern int __percpu_down_read(struct percpu_rw_semaphore *, int);
+extern void __percpu_up_read(struct percpu_rw_semaphore *);
+
+static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_rdlock(&sem->lock);
+	preempt_disable();
+}
+
+static inline void percpu_down_read(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_rdlock(&sem->lock);
+}
+
+static inline int percpu_down_read_trylock(struct percpu_rw_semaphore *sem)
+{
+	return !pthread_rwlock_tryrdlock(&sem->lock);
+}
+
+static inline void percpu_up_read_preempt_enable(struct percpu_rw_semaphore *sem)
+{
+	preempt_enable();
+	pthread_rwlock_unlock(&sem->lock);
+}
+
+static inline void percpu_up_read(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_unlock(&sem->lock);
+}
+
+static inline void percpu_down_write(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_wrlock(&sem->lock);
+}
+
+static inline void percpu_up_write(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_unlock(&sem->lock);
+}
+
+static inline void percpu_free_rwsem(struct percpu_rw_semaphore *sem) {}
+
+static inline int percpu_init_rwsem(struct percpu_rw_semaphore *sem)
+{
+	pthread_rwlock_init(&sem->lock, NULL);
+	return 0;
+}
+
+#define percpu_rwsem_assert_held(sem)		do {} while (0)
+
+#endif
diff --git a/include/linux/string.h b/include/linux/string.h
index abc191e7..ec35b8df 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -9,6 +9,7 @@ extern size_t strlcpy(char *dest, const char *src, size_t size);
 extern char *skip_spaces(const char *);
 extern char *strim(char *);
 extern void memzero_explicit(void *, size_t);
+int match_string(const char * const *, size_t, const char *);
 
 #define kstrndup(s, n, gfp)		strndup(s, n)
 
diff --git a/include/trace/events/bcachefs.h b/include/trace/events/bcachefs.h
index a34574ca..13264b82 100644
--- a/include/trace/events/bcachefs.h
+++ b/include/trace/events/bcachefs.h
@@ -296,6 +296,11 @@ DEFINE_EVENT(btree_node, btree_compact,
 	TP_ARGS(c, b)
 );
 
+DEFINE_EVENT(btree_node, btree_merge,
+	TP_PROTO(struct bch_fs *c, struct btree *b),
+	TP_ARGS(c, b)
+);
+
 DEFINE_EVENT(btree_node, btree_set_root,
 	TP_PROTO(struct bch_fs *c, struct btree *b),
 	TP_ARGS(c, b)
diff --git a/libbcachefs/acl.c b/libbcachefs/acl.c
index d29bdafa..29774e5d 100644
--- a/libbcachefs/acl.c
+++ b/libbcachefs/acl.c
@@ -176,34 +176,19 @@ struct posix_acl *bch2_get_acl(struct inode *vinode, int type)
 	return acl;
 }
 
-int bch2_set_acl(struct inode *vinode, struct posix_acl *acl, int type)
+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) {
-		ret = posix_acl_update_mode(&inode->v, &mode, &acl);
-		if (ret)
-			return ret;
-	}
-
 	switch (type) {
 	case ACL_TYPE_ACCESS:
 		name_index = BCH_XATTR_INDEX_POSIX_ACL_ACCESS;
-		if (acl) {
-			ret = posix_acl_equiv_mode(acl, &inode->v.i_mode);
-			if (ret < 0)
-				return ret;
-			if (ret == 0)
-				acl = NULL;
-		}
 		break;
-
 	case ACL_TYPE_DEFAULT:
 		name_index = BCH_XATTR_INDEX_POSIX_ACL_DEFAULT;
 		if (!S_ISDIR(inode->v.i_mode))
@@ -220,20 +205,7 @@ int bch2_set_acl(struct inode *vinode, struct posix_acl *acl, int type)
 			return (int)PTR_ERR(value);
 	}
 
-	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)
@@ -245,4 +217,33 @@ err:
 	return ret;
 }
 
+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 ret;
+
+	if (type == ACL_TYPE_ACCESS && acl) {
+		ret = posix_acl_update_mode(&inode->v, &mode, &acl);
+		if (ret)
+			return ret;
+	}
+
+	ret = __bch2_set_acl(vinode, acl, type);
+	if (ret)
+		return ret;
+
+	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);
+	}
+
+	return ret;
+}
+
 #endif /* CONFIG_BCACHEFS_POSIX_ACL */
diff --git a/libbcachefs/acl.h b/libbcachefs/acl.h
index b721330e..a66338d4 100644
--- a/libbcachefs/acl.h
+++ b/libbcachefs/acl.h
@@ -52,10 +52,16 @@ static inline int bch2_acl_count(size_t size)
 struct posix_acl;
 
 extern struct posix_acl *bch2_get_acl(struct inode *, int);
+extern int __bch2_set_acl(struct inode *, struct posix_acl *, int);
 extern int bch2_set_acl(struct inode *, struct posix_acl *, int);
 
 #else
 
+static inline int __bch2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
+{
+	return 0;
+}
+
 static inline int bch2_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 {
 	return 0;
diff --git a/libbcachefs/alloc.c b/libbcachefs/alloc.c
index 44f9479e..ac2c7d1f 100644
--- a/libbcachefs/alloc.c
+++ b/libbcachefs/alloc.c
@@ -223,7 +223,7 @@ static void bch2_alloc_read_key(struct bch_fs *c, struct bkey_s_c k)
 	if (a.k->p.offset >= ca->mi.nbuckets)
 		return;
 
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 
 	g = bucket(ca, a.k->p.offset);
 	bucket_cmpxchg(g, new, ({
@@ -237,7 +237,7 @@ static void bch2_alloc_read_key(struct bch_fs *c, struct bkey_s_c k)
 	if (a.v->fields & (1 << BCH_ALLOC_FIELD_WRITE_TIME))
 		g->io_time[WRITE] = get_alloc_field(&d, 2);
 
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 }
 
 int bch2_alloc_read(struct bch_fs *c, struct list_head *journal_replay_list)
@@ -288,7 +288,7 @@ int bch2_alloc_read(struct bch_fs *c, struct list_head *journal_replay_list)
 
 static int __bch2_alloc_write_key(struct bch_fs *c, struct bch_dev *ca,
 				  size_t b, struct btree_iter *iter,
-				  u64 *journal_seq)
+				  u64 *journal_seq, bool nowait)
 {
 	struct bucket_mark m;
 	__BKEY_PADDED(k, DIV_ROUND_UP(sizeof(struct bch_alloc), 8)) alloc_key;
@@ -296,6 +296,13 @@ static int __bch2_alloc_write_key(struct bch_fs *c, struct bch_dev *ca,
 	struct bkey_i_alloc *a;
 	u8 *d;
 	int ret;
+	unsigned flags = BTREE_INSERT_ATOMIC|
+		BTREE_INSERT_NOFAIL|
+		BTREE_INSERT_USE_RESERVE|
+		BTREE_INSERT_USE_ALLOC_RESERVE;
+
+	if (nowait)
+		flags |= BTREE_INSERT_NOWAIT;
 
 	bch2_btree_iter_set_pos(iter, POS(ca->dev_idx, b));
 
@@ -304,7 +311,7 @@ static int __bch2_alloc_write_key(struct bch_fs *c, struct bch_dev *ca,
 		if (ret)
 			break;
 
-		lg_local_lock(&c->usage_lock);
+		percpu_down_read_preempt_disable(&c->usage_lock);
 		g = bucket(ca, b);
 
 		/* read mark under btree node lock: */
@@ -320,14 +327,9 @@ static int __bch2_alloc_write_key(struct bch_fs *c, struct bch_dev *ca,
 			put_alloc_field(&d, 2, g->io_time[READ]);
 		if (a->v.fields & (1 << BCH_ALLOC_FIELD_WRITE_TIME))
 			put_alloc_field(&d, 2, g->io_time[WRITE]);
-		lg_local_unlock(&c->usage_lock);
+		percpu_up_read_preempt_enable(&c->usage_lock);
 
-		ret = bch2_btree_insert_at(c, NULL, NULL, journal_seq,
-					   BTREE_INSERT_ATOMIC|
-					   BTREE_INSERT_NOFAIL|
-					   BTREE_INSERT_USE_RESERVE|
-					   BTREE_INSERT_USE_ALLOC_RESERVE|
-					   BTREE_INSERT_NOWAIT,
+		ret = bch2_btree_insert_at(c, NULL, NULL, journal_seq, flags,
 					   BTREE_INSERT_ENTRY(iter, &a->k_i));
 		bch2_btree_iter_cond_resched(iter);
 	} while (ret == -EINTR);
@@ -352,7 +354,8 @@ int bch2_alloc_replay_key(struct bch_fs *c, struct bpos pos)
 	bch2_btree_iter_init(&iter, c, BTREE_ID_ALLOC, POS_MIN,
 			     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 
-	ret = __bch2_alloc_write_key(c, ca, pos.offset, &iter, NULL);
+	ret = __bch2_alloc_write_key(c, ca, pos.offset, &iter,
+				     NULL, false);
 	bch2_btree_iter_unlock(&iter);
 	return ret;
 }
@@ -372,7 +375,8 @@ int bch2_alloc_write(struct bch_fs *c)
 
 		down_read(&ca->bucket_lock);
 		for_each_set_bit(bucket, ca->buckets_dirty, ca->mi.nbuckets) {
-			ret = __bch2_alloc_write_key(c, ca, bucket, &iter, NULL);
+			ret = __bch2_alloc_write_key(c, ca, bucket, &iter,
+						     NULL, false);
 			if (ret)
 				break;
 
@@ -583,15 +587,20 @@ static void bch2_invalidate_one_bucket(struct bch_fs *c, struct bch_dev *ca,
 {
 	struct bucket_mark m;
 
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	spin_lock(&c->freelist_lock);
+
 	if (!bch2_invalidate_bucket(c, ca, bucket, &m)) {
 		spin_unlock(&c->freelist_lock);
+		percpu_up_read_preempt_enable(&c->usage_lock);
 		return;
 	}
 
 	verify_not_on_freelist(c, ca, bucket);
 	BUG_ON(!fifo_push(&ca->free_inc, bucket));
+
 	spin_unlock(&c->freelist_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 
 	/* gc lock held: */
 	bucket_io_clock_reset(c, ca, bucket, READ);
@@ -812,7 +821,8 @@ static void sort_free_inc(struct bch_fs *c, struct bch_dev *ca)
 }
 
 static int bch2_invalidate_free_inc(struct bch_fs *c, struct bch_dev *ca,
-				    u64 *journal_seq, size_t nr)
+				    u64 *journal_seq, size_t nr,
+				    bool nowait)
 {
 	struct btree_iter iter;
 	int ret = 0;
@@ -820,14 +830,12 @@ static int bch2_invalidate_free_inc(struct bch_fs *c, struct bch_dev *ca,
 	bch2_btree_iter_init(&iter, c, BTREE_ID_ALLOC, POS(ca->dev_idx, 0),
 			     BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 
-	/*
-	 * XXX: if ca->nr_invalidated != 0, just return if we'd block doing the
-	 * btree update or journal_res_get
-	 */
+	/* Only use nowait if we've already invalidated at least one bucket: */
 	while (ca->nr_invalidated < min(nr, fifo_used(&ca->free_inc))) {
 		size_t b = fifo_idx_entry(&ca->free_inc, ca->nr_invalidated);
 
-		ret = __bch2_alloc_write_key(c, ca, b, &iter, journal_seq);
+		ret = __bch2_alloc_write_key(c, ca, b, &iter, journal_seq,
+					     nowait && ca->nr_invalidated);
 		if (ret)
 			break;
 
@@ -835,7 +843,9 @@ static int bch2_invalidate_free_inc(struct bch_fs *c, struct bch_dev *ca,
 	}
 
 	bch2_btree_iter_unlock(&iter);
-	return ret;
+
+	/* If we used NOWAIT, don't return the error: */
+	return ca->nr_invalidated ? 0 : ret;
 }
 
 static bool __push_invalidated_bucket(struct bch_fs *c, struct bch_dev *ca, size_t bucket)
@@ -943,7 +953,8 @@ static int bch2_allocator_thread(void *arg)
 				 fifo_used(&ca->free_inc));
 
 			journal_seq = 0;
-			ret = bch2_invalidate_free_inc(c, ca, &journal_seq, SIZE_MAX);
+			ret = bch2_invalidate_free_inc(c, ca, &journal_seq,
+						       SIZE_MAX, true);
 			if (ret) {
 				bch_err(ca, "error invalidating buckets: %i", ret);
 				goto stop;
@@ -1077,11 +1088,15 @@ void __bch2_open_bucket_put(struct bch_fs *c, struct open_bucket *ob)
 {
 	struct bch_dev *ca = bch_dev_bkey_exists(c, ob->ptr.dev);
 
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	spin_lock(&ob->lock);
+
 	bch2_mark_alloc_bucket(c, ca, PTR_BUCKET_NR(ca, &ob->ptr),
 			       false, gc_pos_alloc(c, ob), 0);
 	ob->valid = false;
+
 	spin_unlock(&ob->lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 
 	spin_lock(&c->freelist_lock);
 	ob->freelist = c->open_buckets_freelist;
@@ -1151,6 +1166,7 @@ int bch2_bucket_alloc(struct bch_fs *c, struct bch_dev *ca,
 	long bucket;
 
 	spin_lock(&c->freelist_lock);
+
 	if (may_alloc_partial &&
 	    ca->open_buckets_partial_nr) {
 		int ret = ca->open_buckets_partial[--ca->open_buckets_partial_nr];
@@ -1202,7 +1218,6 @@ out:
 	ob = bch2_open_bucket_alloc(c);
 
 	spin_lock(&ob->lock);
-	lg_local_lock(&c->usage_lock);
 	buckets = bucket_array(ca);
 
 	ob->valid	= true;
@@ -1215,8 +1230,6 @@ out:
 
 	bucket_io_clock_reset(c, ca, bucket, READ);
 	bucket_io_clock_reset(c, ca, bucket, WRITE);
-
-	lg_local_unlock(&c->usage_lock);
 	spin_unlock(&ob->lock);
 
 	spin_unlock(&c->freelist_lock);
@@ -1296,7 +1309,6 @@ static enum bucket_alloc_ret bch2_bucket_alloc_set(struct bch_fs *c,
 	if (nr_ptrs_effective >= nr_replicas)
 		return ALLOC_SUCCESS;
 
-	rcu_read_lock();
 	devs_sorted = bch2_wp_alloc_list(c, wp, devs);
 
 	for (i = 0; i < devs_sorted.nr; i++) {
@@ -1337,7 +1349,6 @@ static enum bucket_alloc_ret bch2_bucket_alloc_set(struct bch_fs *c,
 			break;
 		}
 	}
-	rcu_read_unlock();
 
 	EBUG_ON(reserve == RESERVE_MOVINGGC &&
 		ret != ALLOC_SUCCESS &&
@@ -1422,8 +1433,13 @@ static int open_bucket_add_buckets(struct bch_fs *c,
 				   struct closure *cl)
 {
 	struct bch_devs_mask devs = c->rw_devs[wp->type];
+	const struct bch_devs_mask *t;
 	struct open_bucket *ob;
 	unsigned i;
+	int ret;
+
+	percpu_down_read_preempt_disable(&c->usage_lock);
+	rcu_read_lock();
 
 	/* Don't allocate from devices we already have pointers to: */
 	for (i = 0; i < devs_have->nr; i++)
@@ -1432,17 +1448,16 @@ static int open_bucket_add_buckets(struct bch_fs *c,
 	writepoint_for_each_ptr_all(wp, ob, i)
 		__clear_bit(ob->ptr.dev, devs.d);
 
-	if (target) {
-		const struct bch_devs_mask *t;
+	t = bch2_target_to_mask(c, target);
+	if (t)
+		bitmap_and(devs.d, devs.d, t->d, BCH_SB_MEMBERS_MAX);
 
-		rcu_read_lock();
-		t = bch2_target_to_mask(c, target);
-		if (t)
-			bitmap_and(devs.d, devs.d, t->d, BCH_SB_MEMBERS_MAX);
-		rcu_read_unlock();
-	}
+	ret = bch2_bucket_alloc_set(c, wp, nr_replicas, reserve, &devs, cl);
 
-	return bch2_bucket_alloc_set(c, wp, nr_replicas, reserve, &devs, cl);
+	rcu_read_unlock();
+	percpu_up_read_preempt_enable(&c->usage_lock);
+
+	return ret;
 }
 
 static struct write_point *__writepoint_find(struct hlist_head *head,
@@ -1980,10 +1995,12 @@ static int __bch2_fs_allocator_start(struct bch_fs *c)
 			if (!is_available_bucket(m) || m.cached_sectors)
 				continue;
 
+			percpu_down_read_preempt_disable(&c->usage_lock);
 			bch2_mark_alloc_bucket(c, ca, bu, true,
 					gc_pos_alloc(c, NULL),
 					BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE|
 					BCH_BUCKET_MARK_GC_LOCK_HELD);
+			percpu_up_read_preempt_enable(&c->usage_lock);
 
 			fifo_push(&ca->free_inc, bu);
 			ca->nr_invalidated++;
@@ -2051,7 +2068,8 @@ not_enough:
 
 	for_each_rw_member(ca, c, dev_iter) {
 		ret = bch2_invalidate_free_inc(c, ca, &journal_seq,
-					       ca->free[RESERVE_BTREE].size);
+					       ca->free[RESERVE_BTREE].size,
+					       false);
 		if (ret) {
 			percpu_ref_put(&ca->io_ref);
 			return ret;
diff --git a/libbcachefs/bcachefs.h b/libbcachefs/bcachefs.h
index 4219c46c..4702b016 100644
--- a/libbcachefs/bcachefs.h
+++ b/libbcachefs/bcachefs.h
@@ -182,10 +182,10 @@
 #include <linux/bio.h>
 #include <linux/closure.h>
 #include <linux/kobject.h>
-#include <linux/lglock.h>
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/percpu-refcount.h>
+#include <linux/percpu-rwsem.h>
 #include <linux/rhashtable.h>
 #include <linux/rwsem.h>
 #include <linux/seqlock.h>
@@ -302,21 +302,14 @@ enum bch_time_stats {
 #include "rebalance_types.h"
 #include "super_types.h"
 
-/*
- * Number of nodes we might have to allocate in a worst case btree split
- * operation - we split all the way up to the root, then allocate a new root.
- */
-#define btree_reserve_required_nodes(depth)	(((depth) + 1) * 2 + 1)
-
 /* Number of nodes btree coalesce will try to coalesce at once */
 #define GC_MERGE_NODES		4U
 
 /* Maximum number of nodes we might need to allocate atomically: */
-#define BTREE_RESERVE_MAX						\
-	(btree_reserve_required_nodes(BTREE_MAX_DEPTH) + GC_MERGE_NODES)
+#define BTREE_RESERVE_MAX	(BTREE_MAX_DEPTH + (BTREE_MAX_DEPTH - 1))
 
 /* Size of the freelist we allocate btree nodes from: */
-#define BTREE_NODE_RESERVE		(BTREE_RESERVE_MAX * 4)
+#define BTREE_NODE_RESERVE	(BTREE_RESERVE_MAX * 4)
 
 struct btree;
 
@@ -591,7 +584,7 @@ struct bch_fs {
 
 	struct bch_fs_usage __percpu *usage_percpu;
 	struct bch_fs_usage	usage_cached;
-	struct lglock		usage_lock;
+	struct percpu_rw_semaphore usage_lock;
 
 	struct closure_waitlist	freelist_wait;
 
diff --git a/libbcachefs/btree_gc.c b/libbcachefs/btree_gc.c
index cd5ebfbe..02b14e38 100644
--- a/libbcachefs/btree_gc.c
+++ b/libbcachefs/btree_gc.c
@@ -118,20 +118,17 @@ static u8 bch2_gc_mark_key(struct bch_fs *c, enum bkey_type type,
 			   struct bkey_s_c k, unsigned flags)
 {
 	struct gc_pos pos = { 0 };
-	struct bch_fs_usage *stats;
 	u8 ret = 0;
 
-	preempt_disable();
-	stats = this_cpu_ptr(c->usage_percpu);
 	switch (type) {
 	case BKEY_TYPE_BTREE:
-		bch2_mark_key(c, k, c->opts.btree_node_size, true, pos, stats,
+		bch2_mark_key(c, k, c->opts.btree_node_size, true, pos, NULL,
 			      0, flags|
 			      BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE|
 			      BCH_BUCKET_MARK_GC_LOCK_HELD);
 		break;
 	case BKEY_TYPE_EXTENTS:
-		bch2_mark_key(c, k, k.k->size, false, pos, stats,
+		bch2_mark_key(c, k, k.k->size, false, pos, NULL,
 			      0, flags|
 			      BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE|
 			      BCH_BUCKET_MARK_GC_LOCK_HELD);
@@ -140,7 +137,6 @@ static u8 bch2_gc_mark_key(struct bch_fs *c, enum bkey_type type,
 	default:
 		BUG();
 	}
-	preempt_enable();
 
 	return ret;
 }
@@ -320,8 +316,10 @@ void bch2_mark_dev_superblock(struct bch_fs *c, struct bch_dev *ca,
 	unsigned i;
 	u64 b;
 
-	if (c)
+	if (c) {
 		lockdep_assert_held(&c->sb_lock);
+		percpu_down_read_preempt_disable(&c->usage_lock);
+	}
 
 	for (i = 0; i < layout->nr_superblocks; i++) {
 		u64 offset = le64_to_cpu(layout->sb_offset[i]);
@@ -345,8 +343,10 @@ void bch2_mark_dev_superblock(struct bch_fs *c, struct bch_dev *ca,
 					  gc_phase(GC_PHASE_SB), flags);
 	}
 
-	if (c)
+	if (c) {
+		percpu_up_read_preempt_enable(&c->usage_lock);
 		spin_unlock(&c->journal.lock);
+	}
 }
 
 static void bch2_mark_superblocks(struct bch_fs *c)
@@ -397,6 +397,8 @@ static void bch2_mark_allocator_buckets(struct bch_fs *c)
 	size_t i, j, iter;
 	unsigned ci;
 
+	percpu_down_read_preempt_disable(&c->usage_lock);
+
 	spin_lock(&c->freelist_lock);
 	gc_pos_set(c, gc_pos_alloc(c, NULL));
 
@@ -433,6 +435,8 @@ static void bch2_mark_allocator_buckets(struct bch_fs *c)
 		}
 		spin_unlock(&ob->lock);
 	}
+
+	percpu_up_read_preempt_enable(&c->usage_lock);
 }
 
 static void bch2_gc_start(struct bch_fs *c)
@@ -444,7 +448,7 @@ static void bch2_gc_start(struct bch_fs *c)
 	size_t b;
 	int cpu;
 
-	lg_global_lock(&c->usage_lock);
+	percpu_down_write(&c->usage_lock);
 
 	/*
 	 * Indicates to buckets code that gc is now in progress - done under
@@ -470,7 +474,7 @@ static void bch2_gc_start(struct bch_fs *c)
 		memset(p->s, 0, sizeof(p->s));
 	}
 
-	lg_global_unlock(&c->usage_lock);
+	percpu_up_write(&c->usage_lock);
 
 	/* Clear bucket marks: */
 	for_each_member_device(ca, c, i) {
diff --git a/libbcachefs/btree_iter.c b/libbcachefs/btree_iter.c
index 70c3132e..95ee9f61 100644
--- a/libbcachefs/btree_iter.c
+++ b/libbcachefs/btree_iter.c
@@ -152,7 +152,7 @@ bool __bch2_btree_node_lock(struct btree *b, struct bpos pos,
 	 * the prev sibling in btree node merging:
 	 */
 	if (iter->nodes_locked &&
-	    __ffs(iter->nodes_locked) == level &&
+	    __ffs(iter->nodes_locked) <= level &&
 	    __btree_iter_cmp(iter->btree_id, pos, iter))
 		return false;
 
@@ -592,6 +592,8 @@ static inline void __btree_iter_init(struct btree_iter *iter,
 	/* Skip to first non whiteout: */
 	if (b->level)
 		bch2_btree_node_iter_peek(&l->iter, b);
+
+	btree_iter_set_dirty(iter, BTREE_ITER_NEED_PEEK);
 }
 
 static inline void btree_iter_node_set(struct btree_iter *iter,
@@ -1084,6 +1086,8 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 	EBUG_ON(!!(iter->flags & BTREE_ITER_IS_EXTENTS) !=
 		(iter->btree_id == BTREE_ID_EXTENTS));
 	EBUG_ON(iter->flags & BTREE_ITER_SLOTS);
+	EBUG_ON(iter->uptodate == BTREE_ITER_UPTODATE &&
+		!btree_node_locked(iter, 0));
 
 	if (iter->uptodate == BTREE_ITER_UPTODATE) {
 		struct bkey_packed *k =
@@ -1093,8 +1097,6 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 			.v = bkeyp_val(&l->b->format, k)
 		};
 
-		EBUG_ON(!btree_node_locked(iter, 0));
-
 		if (debug_check_bkeys(iter->c))
 			bch2_bkey_debugcheck(iter->c, l->b, ret);
 		return ret;
@@ -1257,16 +1259,16 @@ struct bkey_s_c bch2_btree_iter_peek_slot(struct btree_iter *iter)
 	EBUG_ON(!!(iter->flags & BTREE_ITER_IS_EXTENTS) !=
 		(iter->btree_id == BTREE_ID_EXTENTS));
 	EBUG_ON(!(iter->flags & BTREE_ITER_SLOTS));
+	EBUG_ON(iter->uptodate == BTREE_ITER_UPTODATE &&
+		!btree_node_locked(iter, 0));
 
 	if (iter->uptodate == BTREE_ITER_UPTODATE) {
-		struct bkey_s_c ret = { .k = &iter->k };;
+		struct bkey_s_c ret = { .k = &iter->k };
 
 		if (!bkey_deleted(&iter->k))
 			ret.v = bkeyp_val(&l->b->format,
 				__bch2_btree_node_iter_peek_all(&l->iter, l->b));
 
-		EBUG_ON(!btree_node_locked(iter, 0));
-
 		if (debug_check_bkeys(iter->c))
 			bch2_bkey_debugcheck(iter->c, l->b, ret);
 		return ret;
diff --git a/libbcachefs/btree_update_interior.c b/libbcachefs/btree_update_interior.c
index c3ecc1e9..92e19c4e 100644
--- a/libbcachefs/btree_update_interior.c
+++ b/libbcachefs/btree_update_interior.c
@@ -1564,11 +1564,15 @@ int bch2_btree_split_leaf(struct bch_fs *c, struct btree_iter *iter,
 	struct btree_update *as;
 	struct closure cl;
 	int ret = 0;
+	struct btree_iter *linked;
 
 	/*
 	 * We already have a disk reservation and open buckets pinned; this
 	 * allocation must not block:
 	 */
+	for_each_linked_btree_iter(iter, linked)
+		if (linked->btree_id == BTREE_ID_EXTENTS)
+			btree_reserve_flags |= BTREE_INSERT_USE_RESERVE;
 	if (iter->btree_id == BTREE_ID_EXTENTS)
 		btree_reserve_flags |= BTREE_INSERT_USE_RESERVE;
 
@@ -1704,15 +1708,17 @@ retry:
 	}
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     BTREE_INSERT_NOFAIL|
-				     BTREE_INSERT_USE_RESERVE,
-				     &cl);
+			 btree_update_reserve_required(c, parent) + 1,
+			 BTREE_INSERT_NOFAIL|
+			 BTREE_INSERT_USE_RESERVE,
+			 &cl);
 	if (IS_ERR(as)) {
 		ret = PTR_ERR(as);
 		goto out_unlock;
 	}
 
+	trace_btree_merge(c, b);
+
 	bch2_btree_interior_update_will_free_node(as, b);
 	bch2_btree_interior_update_will_free_node(as, m);
 
@@ -1778,8 +1784,10 @@ static int __btree_node_rewrite(struct bch_fs *c, struct btree_iter *iter,
 	struct btree_update *as;
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     flags, cl);
+		(parent
+		 ? btree_update_reserve_required(c, parent)
+		 : 0) + 1,
+		flags, cl);
 	if (IS_ERR(as)) {
 		trace_btree_gc_rewrite_node_fail(c, b);
 		return PTR_ERR(as);
@@ -1966,6 +1974,7 @@ static void __bch2_btree_node_update_key(struct bch_fs *c,
 int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 			       struct btree *b, struct bkey_i_extent *new_key)
 {
+	struct btree *parent = btree_node_parent(iter, b);
 	struct btree_update *as = NULL;
 	struct btree *new_hash = NULL;
 	struct closure cl;
@@ -2003,11 +2012,12 @@ int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 	}
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     BTREE_INSERT_NOFAIL|
-				     BTREE_INSERT_USE_RESERVE|
-				     BTREE_INSERT_USE_ALLOC_RESERVE,
-				     &cl);
+		parent ? btree_update_reserve_required(c, parent) : 0,
+		BTREE_INSERT_NOFAIL|
+		BTREE_INSERT_USE_RESERVE|
+		BTREE_INSERT_USE_ALLOC_RESERVE,
+		&cl);
+
 	if (IS_ERR(as)) {
 		ret = PTR_ERR(as);
 		if (ret == -EAGAIN)
diff --git a/libbcachefs/btree_update_interior.h b/libbcachefs/btree_update_interior.h
index 25bfc7ab..abf14e4c 100644
--- a/libbcachefs/btree_update_interior.h
+++ b/libbcachefs/btree_update_interior.h
@@ -183,9 +183,14 @@ void bch2_btree_root_alloc(struct bch_fs *, enum btree_id);
 static inline unsigned btree_update_reserve_required(struct bch_fs *c,
 						     struct btree *b)
 {
-	unsigned depth = btree_node_root(c, b)->level - b->level;
+	unsigned depth = btree_node_root(c, b)->level - b->level + 1;
 
-	return btree_reserve_required_nodes(depth);
+	/*
+	 * Number of nodes we might have to allocate in a worst case btree
+	 * split operation - we split all the way up to the root, then allocate
+	 * a new root.
+	 */
+	return depth * 2 + 1;
 }
 
 static inline void btree_node_reset_sib_u64s(struct btree *b)
diff --git a/libbcachefs/buckets.c b/libbcachefs/buckets.c
index 5dda22c7..b17189ee 100644
--- a/libbcachefs/buckets.c
+++ b/libbcachefs/buckets.c
@@ -331,7 +331,7 @@ void bch2_fs_usage_apply(struct bch_fs *c,
 		stats->online_reserved	-= added;
 	}
 
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	/* online_reserved not subject to gc: */
 	this_cpu_ptr(c->usage_percpu)->online_reserved +=
 		stats->online_reserved;
@@ -341,7 +341,7 @@ void bch2_fs_usage_apply(struct bch_fs *c,
 		bch2_usage_add(this_cpu_ptr(c->usage_percpu), stats);
 
 	bch2_fs_stats_verify(c);
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 
 	memset(stats, 0, sizeof(*stats));
 }
@@ -352,7 +352,7 @@ static void bch2_dev_usage_update(struct bch_fs *c, struct bch_dev *ca,
 	struct bch_dev_usage *dev_usage;
 
 	if (c)
-		lockdep_assert_held(&c->usage_lock);
+		percpu_rwsem_assert_held(&c->usage_lock);
 
 	if (old.data_type && new.data_type &&
 	    old.data_type != new.data_type) {
@@ -399,12 +399,13 @@ bool bch2_invalidate_bucket(struct bch_fs *c, struct bch_dev *ca,
 	struct bucket *g;
 	struct bucket_mark new;
 
-	lg_local_lock(&c->usage_lock);
+	percpu_rwsem_assert_held(&c->usage_lock);
+
 	g = bucket(ca, b);
 
 	*old = bucket_data_cmpxchg(c, ca, g, new, ({
 		if (!is_available_bucket(new)) {
-			lg_local_unlock(&c->usage_lock);
+			percpu_up_read_preempt_enable(&c->usage_lock);
 			return false;
 		}
 
@@ -414,7 +415,6 @@ bool bch2_invalidate_bucket(struct bch_fs *c, struct bch_dev *ca,
 		new.dirty_sectors	= 0;
 		new.gen++;
 	}));
-	lg_local_unlock(&c->usage_lock);
 
 	if (!old->owned_by_allocator && old->cached_sectors)
 		trace_invalidate(ca, bucket_to_sector(ca, b),
@@ -429,19 +429,16 @@ void bch2_mark_alloc_bucket(struct bch_fs *c, struct bch_dev *ca,
 	struct bucket *g;
 	struct bucket_mark old, new;
 
-	lg_local_lock(&c->usage_lock);
+	percpu_rwsem_assert_held(&c->usage_lock);
 	g = bucket(ca, b);
 
 	if (!(flags & BCH_BUCKET_MARK_GC_LOCK_HELD) &&
-	    gc_will_visit(c, pos)) {
-		lg_local_unlock(&c->usage_lock);
+	    gc_will_visit(c, pos))
 		return;
-	}
 
 	old = bucket_data_cmpxchg(c, ca, g, new, ({
 		new.owned_by_allocator	= owned_by_allocator;
 	}));
-	lg_local_unlock(&c->usage_lock);
 
 	BUG_ON(!owned_by_allocator && !old.owned_by_allocator &&
 	       c->gc_pos.phase == GC_PHASE_DONE);
@@ -471,16 +468,14 @@ void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 	BUG_ON(!type);
 
 	if (likely(c)) {
-		lg_local_lock(&c->usage_lock);
+		percpu_rwsem_assert_held(&c->usage_lock);
 
 		if (!(flags & BCH_BUCKET_MARK_GC_LOCK_HELD) &&
-		    gc_will_visit(c, pos)) {
-			lg_local_unlock(&c->usage_lock);
+		    gc_will_visit(c, pos))
 			return;
-		}
 	}
 
-	preempt_disable();
+	rcu_read_lock();
 
 	g = bucket(ca, b);
 	old = bucket_data_cmpxchg(c, ca, g, new, ({
@@ -489,10 +484,7 @@ void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 		new.data_type		= type;
 	}));
 
-	preempt_enable();
-
-	if (likely(c))
-		lg_local_unlock(&c->usage_lock);
+	rcu_read_unlock();
 
 	BUG_ON(!(flags & BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE) &&
 	       bucket_became_unavailable(c, old, new));
@@ -654,11 +646,14 @@ void bch2_mark_key(struct bch_fs *c, struct bkey_s_c k,
 	 *    (e.g. the btree node lock, or the relevant allocator lock).
 	 */
 
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	if (!(flags & BCH_BUCKET_MARK_GC_LOCK_HELD) &&
 	    gc_will_visit(c, pos))
 		flags |= BCH_BUCKET_MARK_GC_WILL_VISIT;
 
+	if (!stats)
+		stats = this_cpu_ptr(c->usage_percpu);
+
 	switch (k.k->type) {
 	case BCH_EXTENT:
 	case BCH_EXTENT_CACHED: {
@@ -693,7 +688,7 @@ void bch2_mark_key(struct bch_fs *c, struct bkey_s_c k,
 		break;
 	}
 	}
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 }
 
 /* Disk reservations: */
@@ -711,19 +706,19 @@ static u64 __recalc_sectors_available(struct bch_fs *c)
 /* Used by gc when it's starting: */
 void bch2_recalc_sectors_available(struct bch_fs *c)
 {
-	lg_global_lock(&c->usage_lock);
+	percpu_down_write(&c->usage_lock);
 	atomic64_set(&c->sectors_available, __recalc_sectors_available(c));
-	lg_global_unlock(&c->usage_lock);
+	percpu_up_write(&c->usage_lock);
 }
 
 void __bch2_disk_reservation_put(struct bch_fs *c, struct disk_reservation *res)
 {
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	this_cpu_sub(c->usage_percpu->online_reserved,
 		     res->sectors);
 
 	bch2_fs_stats_verify(c);
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 
 	res->sectors = 0;
 }
@@ -738,7 +733,7 @@ int bch2_disk_reservation_add(struct bch_fs *c, struct disk_reservation *res,
 	s64 sectors_available;
 	int ret;
 
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	stats = this_cpu_ptr(c->usage_percpu);
 
 	if (sectors <= stats->available_cache)
@@ -750,7 +745,7 @@ int bch2_disk_reservation_add(struct bch_fs *c, struct disk_reservation *res,
 		get = min((u64) sectors + SECTORS_CACHE, old);
 
 		if (get < sectors) {
-			lg_local_unlock(&c->usage_lock);
+			percpu_up_read_preempt_enable(&c->usage_lock);
 			goto recalculate;
 		}
 	} while ((v = atomic64_cmpxchg(&c->sectors_available,
@@ -765,7 +760,7 @@ out:
 
 	bch2_disk_reservations_verify(c, flags);
 	bch2_fs_stats_verify(c);
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 	return 0;
 
 recalculate:
@@ -785,8 +780,8 @@ recalculate:
 		else if (!down_read_trylock(&c->gc_lock))
 			return -EINTR;
 	}
-	lg_global_lock(&c->usage_lock);
 
+	percpu_down_write(&c->usage_lock);
 	sectors_available = __recalc_sectors_available(c);
 
 	if (sectors <= sectors_available ||
@@ -804,7 +799,8 @@ recalculate:
 	}
 
 	bch2_fs_stats_verify(c);
-	lg_global_unlock(&c->usage_lock);
+	percpu_up_write(&c->usage_lock);
+
 	if (!(flags & BCH_DISK_RESERVATION_GC_LOCK_HELD))
 		up_read(&c->gc_lock);
 
@@ -874,7 +870,7 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 	if (resize) {
 		down_write(&c->gc_lock);
 		down_write(&ca->bucket_lock);
-		lg_global_lock(&c->usage_lock);
+		percpu_down_write(&c->usage_lock);
 	}
 
 	old_buckets = bucket_array(ca);
@@ -900,7 +896,7 @@ int bch2_dev_buckets_resize(struct bch_fs *c, struct bch_dev *ca, u64 nbuckets)
 	swap(ca->buckets_dirty, buckets_dirty);
 
 	if (resize)
-		lg_global_unlock(&c->usage_lock);
+		percpu_up_write(&c->usage_lock);
 
 	spin_lock(&c->freelist_lock);
 	for (i = 0; i < RESERVE_NR; i++) {
diff --git a/libbcachefs/buckets.h b/libbcachefs/buckets.h
index aefe6027..4deb6c37 100644
--- a/libbcachefs/buckets.h
+++ b/libbcachefs/buckets.h
@@ -32,7 +32,7 @@ static inline struct bucket_array *bucket_array(struct bch_dev *ca)
 {
 	return rcu_dereference_check(ca->buckets,
 				     !ca->fs ||
-				     lockdep_is_held(&ca->fs->usage_lock) ||
+				     percpu_rwsem_is_held(&ca->fs->usage_lock) ||
 				     lockdep_is_held(&ca->fs->gc_lock) ||
 				     lockdep_is_held(&ca->bucket_lock));
 }
diff --git a/libbcachefs/disk_groups.c b/libbcachefs/disk_groups.c
index cd200cbe..87f3940e 100644
--- a/libbcachefs/disk_groups.c
+++ b/libbcachefs/disk_groups.c
@@ -176,6 +176,8 @@ const struct bch_devs_mask *bch2_target_to_mask(struct bch_fs *c, unsigned targe
 	struct target t = target_decode(target);
 
 	switch (t.type) {
+	case TARGET_NULL:
+		return NULL;
 	case TARGET_DEV: {
 		struct bch_dev *ca = t.dev < c->sb.nr_devices
 			? rcu_dereference(c->devs[t.dev])
diff --git a/libbcachefs/fs-io.c b/libbcachefs/fs-io.c
index 1d9464af..d7b17195 100644
--- a/libbcachefs/fs-io.c
+++ b/libbcachefs/fs-io.c
@@ -1702,6 +1702,7 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter)
 	struct bio *bio;
 	loff_t offset = req->ki_pos;
 	bool sync = is_sync_kiocb(req);
+	size_t shorten;
 	ssize_t ret;
 
 	if ((offset|iter->count) & (block_bytes(c) - 1))
@@ -1709,11 +1710,13 @@ static int bch2_direct_IO_read(struct kiocb *req, struct iov_iter *iter)
 
 	ret = min_t(loff_t, iter->count,
 		    max_t(loff_t, 0, i_size_read(&inode->v) - offset));
-	iov_iter_truncate(iter, round_up(ret, block_bytes(c)));
 
 	if (!ret)
 		return ret;
 
+	shorten = iov_iter_count(iter) - round_up(ret, block_bytes(c));
+	iter->count -= shorten;
+
 	bio = bio_alloc_bioset(GFP_KERNEL,
 			       iov_iter_npages(iter, BIO_MAX_PAGES),
 			       &c->dio_read_bioset);
@@ -1769,6 +1772,8 @@ start:
 		bch2_read(c, rbio_init(bio, opts), inode->v.i_ino);
 	}
 
+	iter->count += shorten;
+
 	if (sync) {
 		closure_sync(&dio->cl);
 		closure_debug_destroy(&dio->cl);
@@ -1822,6 +1827,13 @@ static long bch2_dio_write_loop(struct dio_write *dio)
 		if (unlikely(ret < 0))
 			goto err;
 
+		/* gup might have faulted pages back in: */
+		ret = write_invalidate_inode_pages_range(mapping,
+				req->ki_pos + (dio->iop.op.written << 9),
+				req->ki_pos + iov_iter_count(&dio->iter) - 1);
+		if (unlikely(ret))
+			goto err;
+
 		dio->iop.op.pos = POS(inode->v.i_ino,
 				(req->ki_pos >> 9) + dio->iop.op.written);
 
@@ -2280,7 +2292,7 @@ static long bch2_fcollapse(struct bch_inode_info *inode,
 	loff_t new_size;
 	int ret;
 
-	if ((offset | len) & (PAGE_SIZE - 1))
+	if ((offset | len) & (block_bytes(c) - 1))
 		return -EINVAL;
 
 	bch2_btree_iter_init(&dst, c, BTREE_ID_EXTENTS,
@@ -2354,8 +2366,11 @@ static long bch2_fcollapse(struct bch_inode_info *inode,
 btree_iter_err:
 		if (ret == -EINTR)
 			ret = 0;
-		if (ret)
+		if (ret) {
+			bch2_btree_iter_unlock(&src);
+			bch2_btree_iter_unlock(&dst);
 			goto err_put_sectors_dirty;
+		}
 		/*
 		 * XXX: if we error here we've left data with multiple
 		 * pointers... which isn't a _super_ serious problem...
@@ -2368,7 +2383,7 @@ btree_iter_err:
 	bch2_btree_iter_unlock(&dst);
 
 	ret = bch2_inode_truncate(c, inode->v.i_ino,
-				 round_up(new_size, PAGE_SIZE) >> 9,
+				 round_up(new_size, block_bytes(c)) >> 9,
 				 &i_sectors_hook.hook,
 				 &inode->ei_journal_seq);
 	if (ret)
@@ -2381,9 +2396,6 @@ err_put_sectors_dirty:
 err:
 	pagecache_block_put(&mapping->add_lock);
 	inode_unlock(&inode->v);
-
-	bch2_btree_iter_unlock(&src);
-	bch2_btree_iter_unlock(&dst);
 	return ret;
 }
 
@@ -2483,7 +2495,7 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 					&i_sectors_hook.quota_res,
 					sectors, true);
 			if (unlikely(ret))
-				goto err_put_sectors_dirty;
+				goto btree_iter_err;
 		}
 
 		if (reservation.v.nr_replicas < replicas ||
@@ -2491,7 +2503,7 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 			ret = bch2_disk_reservation_get(c, &disk_res, sectors,
 							replicas, 0);
 			if (unlikely(ret))
-				goto err_put_sectors_dirty;
+				goto btree_iter_err;
 
 			reservation.v.nr_replicas = disk_res.nr_replicas;
 		}
@@ -2503,8 +2515,12 @@ static long bch2_fallocate(struct bch_inode_info *inode, int mode,
 					  BTREE_INSERT_ENTRY(&iter, &reservation.k_i));
 		bch2_disk_reservation_put(c, &disk_res);
 btree_iter_err:
-		if (ret < 0 && ret != -EINTR)
+		if (ret == -EINTR)
+			ret = 0;
+		if (ret) {
+			bch2_btree_iter_unlock(&iter);
 			goto err_put_sectors_dirty;
+		}
 
 	}
 	bch2_btree_iter_unlock(&iter);
@@ -2544,7 +2560,6 @@ btree_iter_err:
 err_put_sectors_dirty:
 	ret = i_sectors_dirty_finish(c, &i_sectors_hook) ?: ret;
 err:
-	bch2_btree_iter_unlock(&iter);
 	pagecache_block_put(&mapping->add_lock);
 	inode_unlock(&inode->v);
 	return ret;
diff --git a/libbcachefs/fs.c b/libbcachefs/fs.c
index fb30f0d9..dc6c651d 100644
--- a/libbcachefs/fs.c
+++ b/libbcachefs/fs.c
@@ -243,13 +243,13 @@ static struct bch_inode_info *bch2_vfs_inode_create(struct bch_fs *c,
 	atomic_long_inc(&c->nr_inodes);
 
 	if (default_acl) {
-		ret = bch2_set_acl(&inode->v, default_acl, ACL_TYPE_DEFAULT);
+		ret = __bch2_set_acl(&inode->v, default_acl, ACL_TYPE_DEFAULT);
 		if (unlikely(ret))
 			goto err;
 	}
 
 	if (acl) {
-		ret = bch2_set_acl(&inode->v, acl, ACL_TYPE_ACCESS);
+		ret = __bch2_set_acl(&inode->v, acl, ACL_TYPE_ACCESS);
 		if (unlikely(ret))
 			goto err;
 	}
diff --git a/libbcachefs/fsck.c b/libbcachefs/fsck.c
index c554a987..048b5c10 100644
--- a/libbcachefs/fsck.c
+++ b/libbcachefs/fsck.c
@@ -747,8 +747,13 @@ up:
 	}
 
 	for_each_btree_key(&iter, c, BTREE_ID_INODES, POS_MIN, 0, k) {
-		if (k.k->type != BCH_INODE_FS ||
-		    !S_ISDIR(le16_to_cpu(bkey_s_c_to_inode(k).v->bi_mode)))
+		if (k.k->type != BCH_INODE_FS)
+			continue;
+
+		if (!S_ISDIR(le16_to_cpu(bkey_s_c_to_inode(k).v->bi_mode)))
+			continue;
+
+		if (!bch2_empty_dir(c, k.k->p.inode))
 			continue;
 
 		if (fsck_err_on(!inode_bitmap_test(&dirs_done, k.k->p.inode), c,
diff --git a/libbcachefs/io.c b/libbcachefs/io.c
index 3762fb92..f26d4041 100644
--- a/libbcachefs/io.c
+++ b/libbcachefs/io.c
@@ -1698,9 +1698,9 @@ noclone:
 	if (!rbio->have_ioref)
 		goto no_device_postclone;
 
-	lg_local_lock(&c->usage_lock);
+	percpu_down_read_preempt_disable(&c->usage_lock);
 	bucket_io_clock_reset(c, ca, PTR_BUCKET_NR(ca, &pick.ptr), READ);
-	lg_local_unlock(&c->usage_lock);
+	percpu_up_read_preempt_enable(&c->usage_lock);
 
 	this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_USER],
 		     bio_sectors(&rbio->bio));
diff --git a/libbcachefs/journal.c b/libbcachefs/journal.c
index ea67af3d..addd51f0 100644
--- a/libbcachefs/journal.c
+++ b/libbcachefs/journal.c
@@ -725,7 +725,10 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 		long bucket;
 
 		if (new_fs) {
+			percpu_down_read_preempt_disable(&c->usage_lock);
 			bucket = bch2_bucket_alloc_new_fs(ca);
+			percpu_up_read_preempt_enable(&c->usage_lock);
+
 			if (bucket < 0) {
 				ret = -ENOSPC;
 				goto err;
@@ -741,8 +744,10 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 			bucket = sector_to_bucket(ca, ob->ptr.offset);
 		}
 
-		if (c)
+		if (c) {
+			percpu_down_read_preempt_disable(&c->usage_lock);
 			spin_lock(&c->journal.lock);
+		}
 
 		__array_insert_item(ja->buckets,		ja->nr, ja->last_idx);
 		__array_insert_item(ja->bucket_seq,		ja->nr, ja->last_idx);
@@ -759,9 +764,6 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 		}
 		ja->nr++;
 
-		if (c)
-			spin_unlock(&c->journal.lock);
-
 		bch2_mark_metadata_bucket(c, ca, bucket, BCH_DATA_JOURNAL,
 				ca->mi.bucket_size,
 				gc_phase(GC_PHASE_SB),
@@ -769,6 +771,11 @@ static int __bch2_set_nr_journal_buckets(struct bch_dev *ca, unsigned nr,
 				? BCH_BUCKET_MARK_MAY_MAKE_UNAVAILABLE
 				: 0);
 
+		if (c) {
+			spin_unlock(&c->journal.lock);
+			percpu_up_read_preempt_enable(&c->usage_lock);
+		}
+
 		if (!new_fs)
 			bch2_open_bucket_put(c, ob);
 	}
diff --git a/libbcachefs/opts.c b/libbcachefs/opts.c
index 8db8096e..8e655bc1 100644
--- a/libbcachefs/opts.c
+++ b/libbcachefs/opts.c
@@ -218,7 +218,7 @@ int bch2_opt_parse(struct bch_fs *c, const struct bch_option *opt,
 			return -ERANGE;
 		break;
 	case BCH_OPT_STR:
-		ret = bch2_read_string_list(val, opt->choices);
+		ret = match_string(opt->choices, -1, val);
 		if (ret < 0)
 			return ret;
 
diff --git a/libbcachefs/six.h b/libbcachefs/six.h
index f518c64c..999c49db 100644
--- a/libbcachefs/six.h
+++ b/libbcachefs/six.h
@@ -1,6 +1,61 @@
 #ifndef _BCACHEFS_SIX_H
 #define _BCACHEFS_SIX_H
 
+/*
+ * Shared/intent/exclusive locks: sleepable read/write locks, much like rw
+ * semaphores, except with a third intermediate state, intent. Basic operations
+ * are:
+ *
+ * six_lock_read(&foo->lock);
+ * six_unlock_read(&foo->lock);
+ *
+ * six_lock_intent(&foo->lock);
+ * six_unlock_intent(&foo->lock);
+ *
+ * six_lock_write(&foo->lock);
+ * six_unlock_write(&foo->lock);
+ *
+ * Intent locks block other intent locks, but do not block read locks, and you
+ * must have an intent lock held before taking a write lock, like so:
+ *
+ * six_lock_intent(&foo->lock);
+ * six_lock_write(&foo->lock);
+ * six_unlock_write(&foo->lock);
+ * six_unlock_intent(&foo->lock);
+ *
+ * Other operations:
+ *
+ *   six_trylock_read()
+ *   six_trylock_intent()
+ *   six_trylock_write()
+ *
+ *   six_lock_downgrade():	convert from intent to read
+ *   six_lock_tryupgrade():	attempt to convert from read to intent
+ *
+ * Locks also embed a sequence number, which is incremented when the lock is
+ * locked or unlocked for write. The current sequence number can be grabbed
+ * while a lock is held from lock->state.seq; then, if you drop the lock you can
+ * use six_relock_(read|intent_write)(lock, seq) to attempt to retake the lock
+ * iff it hasn't been locked for write in the meantime.
+ *
+ * There are also operations that take the lock type as a parameter, where the
+ * type is one of SIX_LOCK_read, SIX_LOCK_intent, or SIX_LOCK_write:
+ *
+ *   six_lock_type(lock, type)
+ *   six_unlock_type(lock, type)
+ *   six_relock(lock, type, seq)
+ *   six_trylock_type(lock, type)
+ *   six_trylock_convert(lock, from, to)
+ *
+ * A lock may be held multiple types by the same thread (for read or intent,
+ * not write) - up to SIX_LOCK_MAX_RECURSE. However, the six locks code does
+ * _not_ implement the actual recursive checks itself though - rather, if your
+ * code (e.g. btree iterator code) knows that the current thread already has a
+ * lock held, and for the correct type, six_lock_increment() may be used to
+ * bump up the counter for that type - the only effect is that one more call to
+ * unlock will be required before the lock is unlocked.
+ */
+
 #include <linux/lockdep.h>
 #include <linux/osq_lock.h>
 #include <linux/sched.h>
@@ -10,21 +65,6 @@
 
 #define SIX_LOCK_SEPARATE_LOCKFNS
 
-/*
- * LOCK STATES:
- *
- * read, intent, write (i.e. shared/intent/exclusive, hence the name)
- *
- * read and write work as with normal read/write locks - a lock can have
- * multiple readers, but write excludes reads and other write locks.
- *
- * Intent does not block read, but it does block other intent locks. The idea is
- * by taking an intent lock, you can then later upgrade to a write lock without
- * dropping your read lock and without deadlocking - because no other thread has
- * the intent lock and thus no other thread could be trying to take the write
- * lock.
- */
-
 union six_lock_state {
 	struct {
 		atomic64_t	counter;
diff --git a/libbcachefs/super.c b/libbcachefs/super.c
index 55da242c..1eab7c77 100644
--- a/libbcachefs/super.c
+++ b/libbcachefs/super.c
@@ -412,7 +412,7 @@ static void bch2_fs_free(struct bch_fs *c)
 	bch2_io_clock_exit(&c->io_clock[WRITE]);
 	bch2_io_clock_exit(&c->io_clock[READ]);
 	bch2_fs_compress_exit(c);
-	lg_lock_free(&c->usage_lock);
+	percpu_free_rwsem(&c->usage_lock);
 	free_percpu(c->usage_percpu);
 	mempool_exit(&c->btree_bounce_pool);
 	bioset_exit(&c->btree_bio);
@@ -643,7 +643,7 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 			    offsetof(struct btree_write_bio, wbio.bio)),
 			BIOSET_NEED_BVECS) ||
 	    !(c->usage_percpu = alloc_percpu(struct bch_fs_usage)) ||
-	    lg_lock_init(&c->usage_lock) ||
+	    percpu_init_rwsem(&c->usage_lock) ||
 	    mempool_init_kvpmalloc_pool(&c->btree_bounce_pool, 1,
 					btree_bytes(c)) ||
 	    bch2_io_clock_init(&c->io_clock[READ]) ||
@@ -1215,6 +1215,8 @@ static int bch2_dev_attach_bdev(struct bch_fs *c, struct bch_sb_handle *sb)
 	if (ret)
 		return ret;
 
+	bch2_dev_sysfs_online(c, ca);
+
 	if (c->sb.nr_devices == 1)
 		bdevname(ca->disk_sb.bdev, c->name);
 	bdevname(ca->disk_sb.bdev, ca->name);
diff --git a/libbcachefs/sysfs.c b/libbcachefs/sysfs.c
index 5e341a71..66b5b9f9 100644
--- a/libbcachefs/sysfs.c
+++ b/libbcachefs/sysfs.c
@@ -921,7 +921,7 @@ STORE(bch2_dev)
 	}
 
 	if (attr == &sysfs_cache_replacement_policy) {
-		ssize_t v = bch2_read_string_list(buf, bch2_cache_replacement_policies);
+		ssize_t v = __sysfs_match_string(bch2_cache_replacement_policies, -1, buf);
 
 		if (v < 0)
 			return v;
diff --git a/libbcachefs/util.c b/libbcachefs/util.c
index 60e1f1ff..e263dd20 100644
--- a/libbcachefs/util.c
+++ b/libbcachefs/util.c
@@ -126,24 +126,6 @@ ssize_t bch2_scnprint_string_list(char *buf, size_t size,
 	return out - buf;
 }
 
-ssize_t bch2_read_string_list(const char *buf, const char * const list[])
-{
-	size_t i, len;
-
-	buf = skip_spaces(buf);
-
-	len = strlen(buf);
-	while (len && isspace(buf[len - 1]))
-		--len;
-
-	for (i = 0; list[i]; i++)
-		if (strlen(list[i]) == len &&
-		    !memcmp(buf, list[i], len))
-			break;
-
-	return list[i] ? i : -EINVAL;
-}
-
 ssize_t bch2_scnprint_flag_list(char *buf, size_t size,
 				const char * const list[], u64 flags)
 {
@@ -178,7 +160,7 @@ u64 bch2_read_flag_list(char *opt, const char * const list[])
 	s = strim(d);
 
 	while ((p = strsep(&s, ","))) {
-		int flag = bch2_read_string_list(p, list);
+		int flag = match_string(list, -1, p);
 		if (flag < 0) {
 			ret = -1;
 			break;
diff --git a/libbcachefs/util.h b/libbcachefs/util.h
index 18491559..487591c4 100644
--- a/libbcachefs/util.h
+++ b/libbcachefs/util.h
@@ -227,57 +227,6 @@ do {									\
 		heap_sift_down(heap, _i, cmp);				\
 } while (0)
 
-/*
- * Simple array based allocator - preallocates a number of elements and you can
- * never allocate more than that, also has no locking.
- *
- * Handy because if you know you only need a fixed number of elements you don't
- * have to worry about memory allocation failure, and sometimes a mempool isn't
- * what you want.
- *
- * We treat the free elements as entries in a singly linked list, and the
- * freelist as a stack - allocating and freeing push and pop off the freelist.
- */
-
-#define DECLARE_ARRAY_ALLOCATOR(type, name, size)			\
-	struct {							\
-		type	*freelist;					\
-		type	data[size];					\
-	} name
-
-#define array_alloc(array)						\
-({									\
-	typeof((array)->freelist) _ret = (array)->freelist;		\
-									\
-	if (_ret)							\
-		(array)->freelist = *((typeof((array)->freelist) *) _ret);\
-									\
-	_ret;								\
-})
-
-#define array_free(array, ptr)						\
-do {									\
-	typeof((array)->freelist) _ptr = ptr;				\
-									\
-	*((typeof((array)->freelist) *) _ptr) = (array)->freelist;	\
-	(array)->freelist = _ptr;					\
-} while (0)
-
-#define array_allocator_init(array)					\
-do {									\
-	typeof((array)->freelist) _i;					\
-									\
-	BUILD_BUG_ON(sizeof((array)->data[0]) < sizeof(void *));	\
-	(array)->freelist = NULL;					\
-									\
-	for (_i = (array)->data;					\
-	     _i < (array)->data + ARRAY_SIZE((array)->data);		\
-	     _i++)							\
-		array_free(array, _i);					\
-} while (0)
-
-#define array_freelist_empty(array)	((array)->freelist == NULL)
-
 #define ANYSINT_MAX(t)							\
 	((((t) 1 << (sizeof(t) * 8 - 2)) - (t) 1) * (t) 2 + (t) 1)
 
@@ -359,8 +308,6 @@ bool bch2_is_zero(const void *, size_t);
 
 ssize_t bch2_scnprint_string_list(char *, size_t, const char * const[], size_t);
 
-ssize_t bch2_read_string_list(const char *, const char * const[]);
-
 ssize_t bch2_scnprint_flag_list(char *, size_t, const char * const[], u64);
 u64 bch2_read_flag_list(char *, const char * const[]);
 
diff --git a/linux/string.c b/linux/string.c
index 0f23f074..4fa3f64b 100644
--- a/linux/string.c
+++ b/linux/string.c
@@ -95,3 +95,19 @@ void memzero_explicit(void *s, size_t count)
 	memset(s, 0, count);
 	barrier_data(s);
 }
+
+int match_string(const char * const *array, size_t n, const char *string)
+{
+	int index;
+	const char *item;
+
+	for (index = 0; index < n; index++) {
+		item = array[index];
+		if (!item)
+			break;
+		if (!strcmp(item, string))
+			return index;
+	}
+
+	return -EINVAL;
+}
diff --git a/tools-util.c b/tools-util.c
index 8474ab06..ca6d89a5 100644
--- a/tools-util.c
+++ b/tools-util.c
@@ -218,7 +218,7 @@ u64 read_file_u64(int dirfd, const char *path)
 ssize_t read_string_list_or_die(const char *opt, const char * const list[],
 				const char *msg)
 {
-	ssize_t v = bch2_read_string_list(opt, list);
+	ssize_t v = match_string(list, -1, opt);
 	if (v < 0)
 		die("Bad %s %s", msg, opt);