Update bcachefs sources to 91e6c3e0d5 bcachefs: Gap buffer for journal keys

11 files changed, 213 insertions, 107 deletions

diff --git a/libbcachefs/bcachefs.h b/libbcachefs/bcachefs.h
index a13845a2..ab6df637 100644
--- a/libbcachefs/bcachefs.h
+++ b/libbcachefs/bcachefs.h
@@ -548,6 +548,12 @@ struct journal_keys {
 		u32		journal_seq;
 		u32		journal_offset;
 	}			*d;
+	/*
+	 * Gap buffer: instead of all the empty space in the array being at the
+	 * end of the buffer - from @nr to @size - the empty space is at @gap.
+	 * This means that sequential insertions are O(n) instead of O(n^2).
+	 */
+	size_t			gap;
 	size_t			nr;
 	size_t			size;
 	u64			journal_seq_base;
diff --git a/libbcachefs/btree_cache.c b/libbcachefs/btree_cache.c
index 0dcdc30c..8e04129a 100644
--- a/libbcachefs/btree_cache.c
+++ b/libbcachefs/btree_cache.c
@@ -281,7 +281,7 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
 	struct btree_cache *bc = &c->btree_cache;
 	struct btree *b, *t;
 	unsigned long nr = sc->nr_to_scan;
-	unsigned long can_free;
+	unsigned long can_free = 0;
 	unsigned long touched = 0;
 	unsigned long freed = 0;
 	unsigned i, flags;
@@ -305,7 +305,6 @@ static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
 	 * succeed, so that inserting keys into the btree can always succeed and
 	 * IO can always make forward progress:
 	 */
-	nr /= btree_pages(c);
 	can_free = btree_cache_can_free(bc);
 	nr = min_t(unsigned long, nr, can_free);
 
@@ -375,13 +374,10 @@ touched:
 
 	mutex_unlock(&bc->lock);
 out:
-	ret = (unsigned long) freed * btree_pages(c);
+	ret = freed;
 	memalloc_nofs_restore(flags);
 out_norestore:
-	trace_btree_cache_scan(sc->nr_to_scan,
-			       sc->nr_to_scan / btree_pages(c),
-			       btree_cache_can_free(bc),
-			       ret);
+	trace_btree_cache_scan(sc->nr_to_scan, can_free, ret);
 	return ret;
 }
 
@@ -395,7 +391,7 @@ static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
 	if (bch2_btree_shrinker_disabled)
 		return 0;
 
-	return btree_cache_can_free(bc) * btree_pages(c);
+	return btree_cache_can_free(bc);
 }
 
 void bch2_fs_btree_cache_exit(struct bch_fs *c)
@@ -482,7 +478,6 @@ int bch2_fs_btree_cache_init(struct bch_fs *c)
 	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;
 	ret = register_shrinker(&bc->shrink);
 out:
 	pr_verbose_init(c->opts, "ret %i", ret);
diff --git a/libbcachefs/buckets.c b/libbcachefs/buckets.c
index 7654ab24..51ed9609 100644
--- a/libbcachefs/buckets.c
+++ b/libbcachefs/buckets.c
@@ -620,13 +620,13 @@ int bch2_mark_alloc(struct btree_trans *trans,
 	return 0;
 }
 
-void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
-			       size_t b, enum bch_data_type data_type,
-			       unsigned sectors, struct gc_pos pos,
-			       unsigned flags)
+int bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
+			      size_t b, enum bch_data_type data_type,
+			      unsigned sectors, struct gc_pos pos,
+			      unsigned flags)
 {
 	struct bucket old, new, *g;
-	bool overflow;
+	int ret = 0;
 
 	BUG_ON(!(flags & BTREE_TRIGGER_GC));
 	BUG_ON(data_type != BCH_DATA_sb &&
@@ -636,7 +636,7 @@ void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 	 * Backup superblock might be past the end of our normal usable space:
 	 */
 	if (b >= ca->mi.nbuckets)
-		return;
+		return 0;
 
 	percpu_down_read(&c->mark_lock);
 	g = gc_bucket(ca, b);
@@ -644,37 +644,43 @@ void bch2_mark_metadata_bucket(struct bch_fs *c, struct bch_dev *ca,
 	bucket_lock(g);
 	old = *g;
 
+	if (bch2_fs_inconsistent_on(g->data_type &&
+			g->data_type != data_type, c,
+			"different types of data in same bucket: %s, %s",
+			bch2_data_types[g->data_type],
+			bch2_data_types[data_type])) {
+		ret = -EIO;
+		goto err;
+	}
+
+	if (bch2_fs_inconsistent_on((u64) g->dirty_sectors + sectors > ca->mi.bucket_size, c,
+			"bucket %u:%zu gen %u data type %s sector count overflow: %u + %u > bucket size",
+			ca->dev_idx, b, g->gen,
+			bch2_data_types[g->data_type ?: data_type],
+			g->dirty_sectors, sectors)) {
+		ret = -EIO;
+		goto err;
+	}
+
+
 	g->data_type = data_type;
 	g->dirty_sectors += sectors;
-	overflow = g->dirty_sectors < sectors;
-
 	new = *g;
+err:
 	bucket_unlock(g);
-
-	bch2_fs_inconsistent_on(old.data_type &&
-				old.data_type != data_type, c,
-		"different types of data in same bucket: %s, %s",
-		bch2_data_types[old.data_type],
-		bch2_data_types[data_type]);
-
-	bch2_fs_inconsistent_on(overflow, c,
-		"bucket %u:%zu gen %u data type %s sector count overflow: %u + %u > U16_MAX",
-		ca->dev_idx, b, new.gen,
-		bch2_data_types[old.data_type ?: data_type],
-		old.dirty_sectors, sectors);
-
-	bch2_dev_usage_update_m(c, ca, old, new, 0, true);
+	if (!ret)
+		bch2_dev_usage_update_m(c, ca, old, new, 0, true);
 	percpu_up_read(&c->mark_lock);
+	return ret;
 }
 
 static s64 ptr_disk_sectors(s64 sectors, struct extent_ptr_decoded p)
 {
 	EBUG_ON(sectors < 0);
 
-	return p.crc.compression_type &&
-		p.crc.compression_type != BCH_COMPRESSION_TYPE_incompressible
+	return crc_is_compressed(p.crc)
 		? DIV_ROUND_UP_ULL(sectors * p.crc.compressed_size,
-			       p.crc.uncompressed_size)
+				   p.crc.uncompressed_size)
 		: sectors;
 }
 
@@ -808,25 +814,22 @@ static int mark_stripe_bucket(struct btree_trans *trans,
 	old = *g;
 
 	ret = check_bucket_ref(c, k, ptr, sectors, data_type,
-			       new.gen, new.data_type,
-			       new.dirty_sectors, new.cached_sectors);
-	if (ret) {
-		bucket_unlock(g);
+			       g->gen, g->data_type,
+			       g->dirty_sectors, g->cached_sectors);
+	if (ret)
 		goto err;
-	}
 
-	new.dirty_sectors += sectors;
 	if (data_type)
-		new.data_type = data_type;
+		g->data_type = data_type;
+	g->dirty_sectors += sectors;
 
 	g->stripe		= k.k->p.offset;
 	g->stripe_redundancy	= s->nr_redundant;
-
 	new = *g;
-	bucket_unlock(g);
-
-	bch2_dev_usage_update_m(c, ca, old, new, journal_seq, true);
 err:
+	bucket_unlock(g);
+	if (!ret)
+		bch2_dev_usage_update_m(c, ca, old, new, journal_seq, true);
 	percpu_up_read(&c->mark_lock);
 	printbuf_exit(&buf);
 	return ret;
@@ -872,29 +875,22 @@ static int bch2_mark_pointer(struct btree_trans *trans,
 
 	percpu_down_read(&c->mark_lock);
 	g = PTR_GC_BUCKET(ca, &p.ptr);
-
 	bucket_lock(g);
 	old = *g;
 
 	bucket_data_type = g->data_type;
-
 	ret = __mark_pointer(trans, k, &p.ptr, sectors,
 			     data_type, g->gen,
 			     &bucket_data_type,
 			     &g->dirty_sectors,
 			     &g->cached_sectors);
-	if (ret) {
-		bucket_unlock(g);
-		goto err;
-	}
-
-	g->data_type = bucket_data_type;
+	if (!ret)
+		g->data_type = bucket_data_type;
 
 	new = *g;
 	bucket_unlock(g);
-
-	bch2_dev_usage_update_m(c, ca, old, new, journal_seq, true);
-err:
+	if (!ret)
+		bch2_dev_usage_update_m(c, ca, old, new, journal_seq, true);
 	percpu_up_read(&c->mark_lock);
 
 	return ret;
diff --git a/libbcachefs/buckets.h b/libbcachefs/buckets.h
index 853bc9dd..656a04b5 100644
--- a/libbcachefs/buckets.h
+++ b/libbcachefs/buckets.h
@@ -194,9 +194,9 @@ bch2_fs_usage_read_short(struct bch_fs *);
 
 void bch2_fs_usage_initialize(struct bch_fs *);
 
-void bch2_mark_metadata_bucket(struct bch_fs *, struct bch_dev *,
-			       size_t, enum bch_data_type, unsigned,
-			       struct gc_pos, unsigned);
+int bch2_mark_metadata_bucket(struct bch_fs *, struct bch_dev *,
+			      size_t, enum bch_data_type, unsigned,
+			      struct gc_pos, unsigned);
 
 int bch2_mark_alloc(struct btree_trans *, struct bkey_s_c, struct bkey_s_c, unsigned);
 int bch2_mark_extent(struct btree_trans *, struct bkey_s_c, struct bkey_s_c, unsigned);
diff --git a/libbcachefs/io.c b/libbcachefs/io.c
index 36929451..223344e1 100644
--- a/libbcachefs/io.c
+++ b/libbcachefs/io.c
@@ -1981,22 +1981,28 @@ static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
 	struct printbuf buf = PRINTBUF;
 	int ret;
 
-	bch2_bkey_val_to_text(&buf, c, k);
-	bch2_fs_inconsistent(c, "Attempting to read from stale dirty pointer: %s", buf.buf);
-
 	bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-			     POS(ptr.dev, PTR_BUCKET_NR(ca, &ptr)),
+			     PTR_BUCKET_POS(c, &ptr),
 			     BTREE_ITER_CACHED);
 
-	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
-	if (ret)
-		goto out;
+	pr_buf(&buf, "Attempting to read from stale dirty pointer:");
+	pr_indent_push(&buf, 2);
+	pr_newline(&buf);
 
 	bch2_bkey_val_to_text(&buf, c, k);
-	bch_err(c, "%s", buf.buf);
-	bch_err(c, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
+	pr_newline(&buf);
+
+	pr_buf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
+
+	ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
+	if (!ret) {
+		pr_newline(&buf);
+		bch2_bkey_val_to_text(&buf, c, k);
+	}
+
+	bch2_fs_inconsistent(c, "%s", buf.buf);
+
 	bch2_trans_iter_exit(trans, &iter);
-out:
 	printbuf_exit(&buf);
 }
 
diff --git a/libbcachefs/journal.c b/libbcachefs/journal.c
index 505e8367..d01b1cd4 100644
--- a/libbcachefs/journal.c
+++ b/libbcachefs/journal.c
@@ -964,6 +964,7 @@ int bch2_set_nr_journal_buckets(struct bch_fs *c, struct bch_dev *ca,
 int bch2_dev_journal_alloc(struct bch_dev *ca)
 {
 	unsigned nr;
+	int ret;
 
 	if (dynamic_fault("bcachefs:add:journal_alloc"))
 		return -ENOMEM;
@@ -980,7 +981,15 @@ int bch2_dev_journal_alloc(struct bch_dev *ca)
 		     min(1 << 13,
 			 (1 << 24) / ca->mi.bucket_size));
 
-	return __bch2_set_nr_journal_buckets(ca, nr, true, NULL);
+	if (ca->fs)
+		mutex_lock(&ca->fs->sb_lock);
+
+	ret = __bch2_set_nr_journal_buckets(ca, nr, true, NULL);
+
+	if (ca->fs)
+		mutex_unlock(&ca->fs->sb_lock);
+
+	return ret;
 }
 
 /* startup/shutdown: */
diff --git a/libbcachefs/journal_sb.c b/libbcachefs/journal_sb.c
index 8efe7b7e..506044e3 100644
--- a/libbcachefs/journal_sb.c
+++ b/libbcachefs/journal_sb.c
@@ -186,7 +186,8 @@ int bch2_journal_buckets_to_sb(struct bch_fs *c, struct bch_dev *ca)
 	struct bch_sb_field_journal_v2 *j;
 	unsigned i, dst = 0, nr = 1;
 
-	lockdep_assert_held(&c->sb_lock);
+	if (c)
+		lockdep_assert_held(&c->sb_lock);
 
 	if (!ja->nr) {
 		bch2_sb_field_delete(&ca->disk_sb, BCH_SB_FIELD_journal);
diff --git a/libbcachefs/recovery.c b/libbcachefs/recovery.c
index ca92fe84..6a92c1a0 100644
--- a/libbcachefs/recovery.c
+++ b/libbcachefs/recovery.c
@@ -72,58 +72,97 @@ static int journal_key_cmp(const struct journal_key *l, const struct journal_key
 	return __journal_key_cmp(l->btree_id, l->level, l->k->k.p, r);
 }
 
-size_t bch2_journal_key_search(struct journal_keys *journal_keys,
+static inline size_t idx_to_pos(struct journal_keys *keys, size_t idx)
+{
+	size_t gap_size = keys->size - keys->nr;
+
+	if (idx >= keys->gap)
+		idx += gap_size;
+	return idx;
+}
+
+static inline struct journal_key *idx_to_key(struct journal_keys *keys, size_t idx)
+{
+	return keys->d + idx_to_pos(keys, idx);
+}
+
+size_t bch2_journal_key_search(struct journal_keys *keys,
 			       enum btree_id id, unsigned level,
 			       struct bpos pos)
 {
-	size_t l = 0, r = journal_keys->nr, m;
+	size_t l = 0, r = keys->nr, m;
 
 	while (l < r) {
 		m = l + ((r - l) >> 1);
-		if (__journal_key_cmp(id, level, pos, &journal_keys->d[m]) > 0)
+		if (__journal_key_cmp(id, level, pos, idx_to_key(keys, m)) > 0)
 			l = m + 1;
 		else
 			r = m;
 	}
 
-	BUG_ON(l < journal_keys->nr &&
-	       __journal_key_cmp(id, level, pos, &journal_keys->d[l]) > 0);
+	BUG_ON(l < keys->nr &&
+	       __journal_key_cmp(id, level, pos, idx_to_key(keys, l)) > 0);
 
 	BUG_ON(l &&
-	       __journal_key_cmp(id, level, pos, &journal_keys->d[l - 1]) <= 0);
+	       __journal_key_cmp(id, level, pos, idx_to_key(keys, l - 1)) <= 0);
 
-	return l;
+	return idx_to_pos(keys, l);
 }
 
 struct bkey_i *bch2_journal_keys_peek(struct bch_fs *c, enum btree_id btree_id,
 				      unsigned level, struct bpos pos)
 {
 	struct journal_keys *keys = &c->journal_keys;
-	struct journal_key *end = keys->d + keys->nr;
-	struct journal_key *k = keys->d +
-		bch2_journal_key_search(keys, btree_id, level, pos);
+	size_t idx = bch2_journal_key_search(keys, btree_id, level, pos);
 
-	while (k < end && k->overwritten)
-		k++;
+	while (idx < keys->size &&
+	       keys->d[idx].overwritten) {
+		idx++;
+		if (idx == keys->gap)
+			idx += keys->size - keys->nr;
+	}
 
-	if (k < end &&
-	    k->btree_id	== btree_id &&
-	    k->level	== level)
-		return k->k;
+	if (idx < keys->size &&
+	    keys->d[idx].btree_id == btree_id &&
+	    keys->d[idx].level == level)
+		return keys->d[idx].k;
 	return NULL;
 }
 
-static void journal_iter_fix(struct bch_fs *c, struct journal_iter *iter, unsigned idx)
+static void journal_iters_fix(struct bch_fs *c)
 {
-	struct bkey_i *n = iter->keys->d[idx].k;
-	struct btree_and_journal_iter *biter =
-		container_of(iter, struct btree_and_journal_iter, journal);
-
-	if (iter->idx > idx ||
-	    (iter->idx == idx &&
-	     biter->last &&
-	     bpos_cmp(n->k.p, biter->unpacked.p) <= 0))
-		iter->idx++;
+	struct journal_keys *keys = &c->journal_keys;
+	/* The key we just inserted is immediately before the gap: */
+	struct journal_key *n = &keys->d[keys->gap - 1];
+	size_t gap_end = keys->gap + (keys->size - keys->nr);
+	struct btree_and_journal_iter *iter;
+
+	/*
+	 * If an iterator points one after the key we just inserted,
+	 * and the key we just inserted compares >= the iterator's position,
+	 * decrement the iterator so it points at the key we just inserted:
+	 */
+	list_for_each_entry(iter, &c->journal_iters, journal.list)
+		if (iter->journal.idx == gap_end &&
+		    iter->last &&
+		    iter->b->c.btree_id == n->btree_id &&
+		    iter->b->c.level	== n->level &&
+		    bpos_cmp(n->k->k.p, iter->unpacked.p) >= 0)
+			iter->journal.idx = keys->gap - 1;
+}
+
+static void journal_iters_move_gap(struct bch_fs *c, size_t old_gap, size_t new_gap)
+{
+	struct journal_keys *keys = &c->journal_keys;
+	struct journal_iter *iter;
+	size_t gap_size = keys->size - keys->nr;
+
+	list_for_each_entry(iter, &c->journal_iters, list) {
+		if (iter->idx > old_gap)
+			iter->idx -= gap_size;
+		if (iter->idx >= new_gap)
+			iter->idx += gap_size;
+	}
 }
 
 int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
@@ -141,12 +180,11 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
 		.journal_seq	= U32_MAX,
 	};
 	struct journal_keys *keys = &c->journal_keys;
-	struct journal_iter *iter;
 	size_t idx = bch2_journal_key_search(keys, id, level, k->k.p);
 
 	BUG_ON(test_bit(BCH_FS_RW, &c->flags));
 
-	if (idx < keys->nr &&
+	if (idx < keys->size &&
 	    journal_key_cmp(&n, &keys->d[idx]) == 0) {
 		if (keys->d[idx].allocated)
 			kfree(keys->d[idx].k);
@@ -154,6 +192,9 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
 		return 0;
 	}
 
+	if (idx > keys->gap)
+		idx -= keys->size - keys->nr;
+
 	if (keys->nr == keys->size) {
 		struct journal_keys new_keys = {
 			.nr			= keys->nr,
@@ -168,15 +209,24 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
 			return -ENOMEM;
 		}
 
+		/* Since @keys was full, there was no gap: */
 		memcpy(new_keys.d, keys->d, sizeof(keys->d[0]) * keys->nr);
 		kvfree(keys->d);
 		*keys = new_keys;
+
+		/* And now the gap is at the end: */
+		keys->gap = keys->nr;
 	}
 
-	array_insert_item(keys->d, keys->nr, idx, n);
+	journal_iters_move_gap(c, keys->gap, idx);
+
+	move_gap(keys->d, keys->nr, keys->size, keys->gap, idx);
+	keys->gap = idx;
+
+	keys->nr++;
+	keys->d[keys->gap++] = n;
 
-	list_for_each_entry(iter, &c->journal_iters, list)
-		journal_iter_fix(c, iter, idx);
+	journal_iters_fix(c);
 
 	return 0;
 }
@@ -220,7 +270,7 @@ void bch2_journal_key_overwritten(struct bch_fs *c, enum btree_id btree,
 	struct journal_keys *keys = &c->journal_keys;
 	size_t idx = bch2_journal_key_search(keys, btree, level, pos);
 
-	if (idx < keys->nr &&
+	if (idx < keys->size &&
 	    keys->d[idx].btree_id	== btree &&
 	    keys->d[idx].level		== level &&
 	    !bpos_cmp(keys->d[idx].k->k.p, pos))
@@ -246,8 +296,11 @@ static struct bkey_i *bch2_journal_iter_peek(struct journal_iter *iter)
 
 static void bch2_journal_iter_advance(struct journal_iter *iter)
 {
-	if (iter->idx < iter->keys->nr)
+	if (iter->idx < iter->keys->size) {
 		iter->idx++;
+		if (iter->idx == iter->keys->gap)
+			iter->idx += iter->keys->size - iter->keys->nr;
+	}
 }
 
 static void bch2_journal_iter_exit(struct journal_iter *iter)
@@ -409,6 +462,9 @@ void bch2_journal_keys_free(struct journal_keys *keys)
 {
 	struct journal_key *i;
 
+	move_gap(keys->d, keys->nr, keys->size, keys->gap, keys->nr);
+	keys->gap = keys->nr;
+
 	for (i = keys->d; i < keys->d + keys->nr; i++)
 		if (i->allocated)
 			kfree(i->k);
@@ -478,6 +534,7 @@ static struct journal_keys journal_keys_sort(struct list_head *journal_entries)
 	}
 
 	keys.nr = dst - keys.d;
+	keys.gap = keys.nr;
 err:
 	return keys;
 }
@@ -538,6 +595,9 @@ static int bch2_journal_replay(struct bch_fs *c)
 	size_t i;
 	int ret;
 
+	move_gap(keys->d, keys->nr, keys->size, keys->gap, keys->nr);
+	keys->gap = keys->nr;
+
 	keys_sorted = kvmalloc_array(sizeof(*keys_sorted), keys->nr, GFP_KERNEL);
 	if (!keys_sorted)
 		return -ENOMEM;
diff --git a/libbcachefs/recovery.h b/libbcachefs/recovery.h
index e6927a91..30580a89 100644
--- a/libbcachefs/recovery.h
+++ b/libbcachefs/recovery.h
@@ -2,9 +2,6 @@
 #ifndef _BCACHEFS_RECOVERY_H
 #define _BCACHEFS_RECOVERY_H
 
-#define for_each_journal_key(keys, i)				\
-	for (i = (keys).d; i < (keys).d + (keys).nr; (i)++)
-
 struct journal_iter {
 	struct list_head	list;
 	enum btree_id		btree_id;
diff --git a/libbcachefs/super-io.c b/libbcachefs/super-io.c
index 71abf871..15241a56 100644
--- a/libbcachefs/super-io.c
+++ b/libbcachefs/super-io.c
@@ -21,6 +21,8 @@
 #include <linux/backing-dev.h>
 #include <linux/sort.h>
 
+#include <trace/events/bcachefs.h>
+
 const char * const bch2_sb_fields[] = {
 #define x(name, nr)	#name,
 	BCH_SB_FIELDS()
@@ -797,6 +799,8 @@ int bch2_write_super(struct bch_fs *c)
 	unsigned degraded_flags = BCH_FORCE_IF_DEGRADED;
 	int ret = 0;
 
+	trace_write_super(c, _RET_IP_);
+
 	if (c->opts.very_degraded)
 		degraded_flags |= BCH_FORCE_IF_LOST;
 
@@ -831,6 +835,13 @@ int bch2_write_super(struct bch_fs *c)
 	if (c->opts.nochanges)
 		goto out;
 
+	/*
+	 * Defer writing the superblock until filesystem initialization is
+	 * complete - don't write out a partly initialized superblock:
+	 */
+	if (!BCH_SB_INITIALIZED(c->disk_sb.sb))
+		goto out;
+
 	for_each_online_member(ca, c, i) {
 		__set_bit(ca->dev_idx, sb_written.d);
 		ca->sb_write_error = 0;
diff --git a/libbcachefs/util.h b/libbcachefs/util.h
index 086d941f..98f70a5c 100644
--- a/libbcachefs/util.h
+++ b/libbcachefs/util.h
@@ -806,6 +806,31 @@ do {									\
 #define array_remove_item(_array, _nr, _pos)				\
 	array_remove_items(_array, _nr, _pos, 1)
 
+static inline void __move_gap(void *array, size_t element_size,
+			      size_t nr, size_t size,
+			      size_t old_gap, size_t new_gap)
+{
+	size_t gap_end = old_gap + size - nr;
+
+	if (new_gap < old_gap) {
+		size_t move = old_gap - new_gap;
+
+		memmove(array + element_size * (gap_end - move),
+			array + element_size * (old_gap - move),
+				element_size * move);
+	} else if (new_gap > old_gap) {
+		size_t move = new_gap - old_gap;
+
+		memmove(array + element_size * old_gap,
+			array + element_size * gap_end,
+				element_size * move);
+	}
+}
+
+/* Move the gap in a gap buffer: */
+#define move_gap(_array, _nr, _size, _old_gap, _new_gap)	\
+	__move_gap(_array, sizeof(_array[0]), _nr, _size, _old_gap, _new_gap)
+
 #define bubble_sort(_base, _nr, _cmp)					\
 do {									\
 	ssize_t _i, _end;						\