Rename from bcache-tools to bcachefs-tools

1 files changed, 817 insertions, 0 deletions

diff --git a/libbcachefs/super-io.c b/libbcachefs/super-io.c
new file mode 100644
index 00000000..9f41d71d
--- /dev/null
+++ b/libbcachefs/super-io.c
@@ -0,0 +1,817 @@
+
+#include "bcachefs.h"
+#include "checksum.h"
+#include "error.h"
+#include "io.h"
+#include "journal.h"
+#include "super-io.h"
+#include "super.h"
+#include "vstructs.h"
+
+#include <linux/backing-dev.h>
+#include <linux/sort.h>
+
+static inline void __bch2_sb_layout_size_assert(void)
+{
+	BUILD_BUG_ON(sizeof(struct bch_sb_layout) != 512);
+}
+
+struct bch_sb_field *bch2_sb_field_get(struct bch_sb *sb,
+				      enum bch_sb_field_type type)
+{
+	struct bch_sb_field *f;
+
+	/* XXX: need locking around superblock to access optional fields */
+
+	vstruct_for_each(sb, f)
+		if (le32_to_cpu(f->type) == type)
+			return f;
+	return NULL;
+}
+
+void bch2_free_super(struct bcache_superblock *sb)
+{
+	if (sb->bio)
+		bio_put(sb->bio);
+	if (!IS_ERR_OR_NULL(sb->bdev))
+		blkdev_put(sb->bdev, sb->mode);
+
+	free_pages((unsigned long) sb->sb, sb->page_order);
+	memset(sb, 0, sizeof(*sb));
+}
+
+static int __bch2_super_realloc(struct bcache_superblock *sb, unsigned order)
+{
+	struct bch_sb *new_sb;
+	struct bio *bio;
+
+	if (sb->page_order >= order && sb->sb)
+		return 0;
+
+	if (dynamic_fault("bcachefs:add:super_realloc"))
+		return -ENOMEM;
+
+	bio = bio_kmalloc(GFP_KERNEL, 1 << order);
+	if (!bio)
+		return -ENOMEM;
+
+	if (sb->bio)
+		bio_put(sb->bio);
+	sb->bio = bio;
+
+	new_sb = (void *) __get_free_pages(GFP_KERNEL, order);
+	if (!new_sb)
+		return -ENOMEM;
+
+	if (sb->sb)
+		memcpy(new_sb, sb->sb, PAGE_SIZE << sb->page_order);
+
+	free_pages((unsigned long) sb->sb, sb->page_order);
+	sb->sb = new_sb;
+
+	sb->page_order = order;
+
+	return 0;
+}
+
+static int bch2_sb_realloc(struct bcache_superblock *sb, unsigned u64s)
+{
+	u64 new_bytes = __vstruct_bytes(struct bch_sb, u64s);
+	u64 max_bytes = 512 << sb->sb->layout.sb_max_size_bits;
+
+	if (new_bytes > max_bytes) {
+		char buf[BDEVNAME_SIZE];
+
+		pr_err("%s: superblock too big: want %llu but have %llu",
+		       bdevname(sb->bdev, buf), new_bytes, max_bytes);
+		return -ENOSPC;
+	}
+
+	return __bch2_super_realloc(sb, get_order(new_bytes));
+}
+
+static int bch2_fs_sb_realloc(struct bch_fs *c, unsigned u64s)
+{
+	u64 bytes = __vstruct_bytes(struct bch_sb, u64s);
+	struct bch_sb *sb;
+	unsigned order = get_order(bytes);
+
+	if (c->disk_sb && order <= c->disk_sb_order)
+		return 0;
+
+	sb = (void *) __get_free_pages(GFP_KERNEL|__GFP_ZERO, order);
+	if (!sb)
+		return -ENOMEM;
+
+	if (c->disk_sb)
+		memcpy(sb, c->disk_sb, PAGE_SIZE << c->disk_sb_order);
+
+	free_pages((unsigned long) c->disk_sb, c->disk_sb_order);
+
+	c->disk_sb = sb;
+	c->disk_sb_order = order;
+	return 0;
+}
+
+static struct bch_sb_field *__bch2_sb_field_resize(struct bch_sb *sb,
+						  struct bch_sb_field *f,
+						  unsigned u64s)
+{
+	unsigned old_u64s = f ? le32_to_cpu(f->u64s) : 0;
+
+	if (!f) {
+		f = vstruct_last(sb);
+		memset(f, 0, sizeof(u64) * u64s);
+		f->u64s = cpu_to_le32(u64s);
+		f->type = 0;
+	} else {
+		void *src, *dst;
+
+		src = vstruct_end(f);
+		f->u64s = cpu_to_le32(u64s);
+		dst = vstruct_end(f);
+
+		memmove(dst, src, vstruct_end(sb) - src);
+
+		if (dst > src)
+			memset(src, 0, dst - src);
+	}
+
+	le32_add_cpu(&sb->u64s, u64s - old_u64s);
+
+	return f;
+}
+
+struct bch_sb_field *bch2_sb_field_resize(struct bcache_superblock *sb,
+					 enum bch_sb_field_type type,
+					 unsigned u64s)
+{
+	struct bch_sb_field *f = bch2_sb_field_get(sb->sb, type);
+	ssize_t old_u64s = f ? le32_to_cpu(f->u64s) : 0;
+	ssize_t d = -old_u64s + u64s;
+
+	if (bch2_sb_realloc(sb, le32_to_cpu(sb->sb->u64s) + d))
+		return NULL;
+
+	f = __bch2_sb_field_resize(sb->sb, f, u64s);
+	f->type = type;
+	return f;
+}
+
+struct bch_sb_field *bch2_fs_sb_field_resize(struct bch_fs *c,
+					    enum bch_sb_field_type type,
+					    unsigned u64s)
+{
+	struct bch_sb_field *f = bch2_sb_field_get(c->disk_sb, type);
+	ssize_t old_u64s = f ? le32_to_cpu(f->u64s) : 0;
+	ssize_t d = -old_u64s + u64s;
+	struct bch_dev *ca;
+	unsigned i;
+
+	lockdep_assert_held(&c->sb_lock);
+
+	if (bch2_fs_sb_realloc(c, le32_to_cpu(c->disk_sb->u64s) + d))
+		return NULL;
+
+	/* XXX: we're not checking that offline device have enough space */
+
+	for_each_online_member(ca, c, i) {
+		struct bcache_superblock *sb = &ca->disk_sb;
+
+		if (bch2_sb_realloc(sb, le32_to_cpu(sb->sb->u64s) + d)) {
+			percpu_ref_put(&ca->ref);
+			return NULL;
+		}
+	}
+
+	f = __bch2_sb_field_resize(c->disk_sb, f, u64s);
+	f->type = type;
+	return f;
+}
+
+static const char *validate_sb_layout(struct bch_sb_layout *layout)
+{
+	u64 offset, prev_offset, max_sectors;
+	unsigned i;
+
+	if (uuid_le_cmp(layout->magic, BCACHE_MAGIC))
+		return "Not a bcachefs superblock layout";
+
+	if (layout->layout_type != 0)
+		return "Invalid superblock layout type";
+
+	if (!layout->nr_superblocks)
+		return "Invalid superblock layout: no superblocks";
+
+	if (layout->nr_superblocks > ARRAY_SIZE(layout->sb_offset))
+		return "Invalid superblock layout: too many superblocks";
+
+	max_sectors = 1 << layout->sb_max_size_bits;
+
+	prev_offset = le64_to_cpu(layout->sb_offset[0]);
+
+	for (i = 1; i < layout->nr_superblocks; i++) {
+		offset = le64_to_cpu(layout->sb_offset[i]);
+
+		if (offset < prev_offset + max_sectors)
+			return "Invalid superblock layout: superblocks overlap";
+		prev_offset = offset;
+	}
+
+	return NULL;
+}
+
+static int u64_cmp(const void *_l, const void *_r)
+{
+	u64 l = *((const u64 *) _l), r = *((const u64 *) _r);
+
+	return l < r ? -1 : l > r ? 1 : 0;
+}
+
+const char *bch2_validate_journal_layout(struct bch_sb *sb,
+					struct bch_member_cpu mi)
+{
+	struct bch_sb_field_journal *journal;
+	const char *err;
+	unsigned nr;
+	unsigned i;
+	u64 *b;
+
+	journal = bch2_sb_get_journal(sb);
+	if (!journal)
+		return NULL;
+
+	nr = bch2_nr_journal_buckets(journal);
+	if (!nr)
+		return NULL;
+
+	b = kmalloc_array(sizeof(u64), nr, GFP_KERNEL);
+	if (!b)
+		return "cannot allocate memory";
+
+	for (i = 0; i < nr; i++)
+		b[i] = le64_to_cpu(journal->buckets[i]);
+
+	sort(b, nr, sizeof(u64), u64_cmp, NULL);
+
+	err = "journal bucket at sector 0";
+	if (!b[0])
+		goto err;
+
+	err = "journal bucket before first bucket";
+	if (b[0] < mi.first_bucket)
+		goto err;
+
+	err = "journal bucket past end of device";
+	if (b[nr - 1] >= mi.nbuckets)
+		goto err;
+
+	err = "duplicate journal buckets";
+	for (i = 0; i + 1 < nr; i++)
+		if (b[i] == b[i + 1])
+			goto err;
+
+	err = NULL;
+err:
+	kfree(b);
+	return err;
+}
+
+static const char *bch2_sb_validate_members(struct bch_sb *sb)
+{
+	struct bch_sb_field_members *mi;
+	unsigned i;
+
+	mi = bch2_sb_get_members(sb);
+	if (!mi)
+		return "Invalid superblock: member info area missing";
+
+	if ((void *) (mi->members + sb->nr_devices) >
+	    vstruct_end(&mi->field))
+		return "Invalid superblock: bad member info";
+
+	for (i = 0; i < sb->nr_devices; i++) {
+		if (bch2_is_zero(mi->members[i].uuid.b, sizeof(uuid_le)))
+			continue;
+
+		if (le16_to_cpu(mi->members[i].bucket_size) <
+		    BCH_SB_BTREE_NODE_SIZE(sb))
+			return "bucket size smaller than btree node size";
+	}
+
+	return NULL;
+}
+
+const char *bch2_validate_cache_super(struct bcache_superblock *disk_sb)
+{
+	struct bch_sb *sb = disk_sb->sb;
+	struct bch_sb_field *f;
+	struct bch_sb_field_members *sb_mi;
+	struct bch_member_cpu mi;
+	const char *err;
+	u16 block_size;
+
+	switch (le64_to_cpu(sb->version)) {
+	case BCACHE_SB_VERSION_CDEV_V4:
+		break;
+	default:
+		return"Unsupported superblock version";
+	}
+
+	if (BCH_SB_INITIALIZED(sb) &&
+	    le64_to_cpu(sb->version) != BCACHE_SB_VERSION_CDEV_V4)
+		return "Unsupported superblock version";
+
+	block_size = le16_to_cpu(sb->block_size);
+
+	if (!is_power_of_2(block_size) ||
+	    block_size > PAGE_SECTORS)
+		return "Bad block size";
+
+	if (bch2_is_zero(sb->user_uuid.b, sizeof(uuid_le)))
+		return "Bad user UUID";
+
+	if (bch2_is_zero(sb->uuid.b, sizeof(uuid_le)))
+		return "Bad internal UUID";
+
+	if (!sb->nr_devices ||
+	    sb->nr_devices <= sb->dev_idx ||
+	    sb->nr_devices > BCH_SB_MEMBERS_MAX)
+		return "Bad cache device number in set";
+
+	if (!BCH_SB_META_REPLICAS_WANT(sb) ||
+	    BCH_SB_META_REPLICAS_WANT(sb) >= BCH_REPLICAS_MAX)
+		return "Invalid number of metadata replicas";
+
+	if (!BCH_SB_META_REPLICAS_REQ(sb) ||
+	    BCH_SB_META_REPLICAS_REQ(sb) >= BCH_REPLICAS_MAX)
+		return "Invalid number of metadata replicas";
+
+	if (!BCH_SB_META_REPLICAS_HAVE(sb) ||
+	    BCH_SB_META_REPLICAS_HAVE(sb) >
+	    BCH_SB_META_REPLICAS_WANT(sb))
+		return "Invalid number of metadata replicas";
+
+	if (!BCH_SB_DATA_REPLICAS_WANT(sb) ||
+	    BCH_SB_DATA_REPLICAS_WANT(sb) >= BCH_REPLICAS_MAX)
+		return "Invalid number of data replicas";
+
+	if (!BCH_SB_DATA_REPLICAS_REQ(sb) ||
+	    BCH_SB_DATA_REPLICAS_REQ(sb) >= BCH_REPLICAS_MAX)
+		return "Invalid number of metadata replicas";
+
+	if (!BCH_SB_DATA_REPLICAS_HAVE(sb) ||
+	    BCH_SB_DATA_REPLICAS_HAVE(sb) >
+	    BCH_SB_DATA_REPLICAS_WANT(sb))
+		return "Invalid number of data replicas";
+
+	if (!BCH_SB_BTREE_NODE_SIZE(sb))
+		return "Btree node size not set";
+
+	if (!is_power_of_2(BCH_SB_BTREE_NODE_SIZE(sb)))
+		return "Btree node size not a power of two";
+
+	if (BCH_SB_BTREE_NODE_SIZE(sb) > BTREE_NODE_SIZE_MAX)
+		return "Btree node size too large";
+
+	if (BCH_SB_GC_RESERVE(sb) < 5)
+		return "gc reserve percentage too small";
+
+	if (1U << BCH_SB_JOURNAL_ENTRY_SIZE(sb) < block_size)
+		return "max journal entry size too small";
+
+	/* 4 mb max: */
+	if (512U << BCH_SB_JOURNAL_ENTRY_SIZE(sb) > JOURNAL_ENTRY_SIZE_MAX)
+		return "max journal entry size too big";
+
+	if (!sb->time_precision ||
+	    le32_to_cpu(sb->time_precision) > NSEC_PER_SEC)
+		return "invalid time precision";
+
+	/* validate layout */
+	err = validate_sb_layout(&sb->layout);
+	if (err)
+		return err;
+
+	vstruct_for_each(sb, f) {
+		if (!f->u64s)
+			return "Invalid superblock: invalid optional field";
+
+		if (vstruct_next(f) > vstruct_last(sb))
+			return "Invalid superblock: invalid optional field";
+
+		if (le32_to_cpu(f->type) >= BCH_SB_FIELD_NR)
+			return "Invalid superblock: unknown optional field type";
+	}
+
+	err = bch2_sb_validate_members(sb);
+	if (err)
+		return err;
+
+	sb_mi = bch2_sb_get_members(sb);
+	mi = bch2_mi_to_cpu(sb_mi->members + sb->dev_idx);
+
+	if (mi.nbuckets > LONG_MAX)
+		return "Too many buckets";
+
+	if (mi.nbuckets - mi.first_bucket < 1 << 10)
+		return "Not enough buckets";
+
+	if (!is_power_of_2(mi.bucket_size) ||
+	    mi.bucket_size < PAGE_SECTORS ||
+	    mi.bucket_size < block_size)
+		return "Bad bucket size";
+
+	if (get_capacity(disk_sb->bdev->bd_disk) <
+	    mi.bucket_size * mi.nbuckets)
+		return "Invalid superblock: device too small";
+
+	err = bch2_validate_journal_layout(sb, mi);
+	if (err)
+		return err;
+
+	return NULL;
+}
+
+/* device open: */
+
+static const char *bch2_blkdev_open(const char *path, fmode_t mode,
+				   void *holder, struct block_device **ret)
+{
+	struct block_device *bdev;
+
+	*ret = NULL;
+	bdev = blkdev_get_by_path(path, mode, holder);
+	if (bdev == ERR_PTR(-EBUSY))
+		return "device busy";
+
+	if (IS_ERR(bdev))
+		return "failed to open device";
+
+	if (mode & FMODE_WRITE)
+		bdev_get_queue(bdev)->backing_dev_info.capabilities
+			|= BDI_CAP_STABLE_WRITES;
+
+	*ret = bdev;
+	return NULL;
+}
+
+static void bch2_sb_update(struct bch_fs *c)
+{
+	struct bch_sb *src = c->disk_sb;
+	struct bch_sb_field_members *mi = bch2_sb_get_members(src);
+	struct bch_dev *ca;
+	unsigned i;
+
+	lockdep_assert_held(&c->sb_lock);
+
+	c->sb.uuid		= src->uuid;
+	c->sb.user_uuid		= src->user_uuid;
+	c->sb.block_size	= le16_to_cpu(src->block_size);
+	c->sb.btree_node_size	= BCH_SB_BTREE_NODE_SIZE(src);
+	c->sb.nr_devices	= src->nr_devices;
+	c->sb.clean		= BCH_SB_CLEAN(src);
+	c->sb.meta_replicas_have= BCH_SB_META_REPLICAS_HAVE(src);
+	c->sb.data_replicas_have= BCH_SB_DATA_REPLICAS_HAVE(src);
+	c->sb.str_hash_type	= BCH_SB_STR_HASH_TYPE(src);
+	c->sb.encryption_type	= BCH_SB_ENCRYPTION_TYPE(src);
+	c->sb.time_base_lo	= le64_to_cpu(src->time_base_lo);
+	c->sb.time_base_hi	= le32_to_cpu(src->time_base_hi);
+	c->sb.time_precision	= le32_to_cpu(src->time_precision);
+
+	for_each_member_device(ca, c, i)
+		ca->mi = bch2_mi_to_cpu(mi->members + i);
+}
+
+/* doesn't copy member info */
+static void __copy_super(struct bch_sb *dst, struct bch_sb *src)
+{
+	struct bch_sb_field *src_f, *dst_f;
+
+	dst->version		= src->version;
+	dst->seq		= src->seq;
+	dst->uuid		= src->uuid;
+	dst->user_uuid		= src->user_uuid;
+	memcpy(dst->label,	src->label, sizeof(dst->label));
+
+	dst->block_size		= src->block_size;
+	dst->nr_devices		= src->nr_devices;
+
+	dst->time_base_lo	= src->time_base_lo;
+	dst->time_base_hi	= src->time_base_hi;
+	dst->time_precision	= src->time_precision;
+
+	memcpy(dst->flags,	src->flags,	sizeof(dst->flags));
+	memcpy(dst->features,	src->features,	sizeof(dst->features));
+	memcpy(dst->compat,	src->compat,	sizeof(dst->compat));
+
+	vstruct_for_each(src, src_f) {
+		if (src_f->type == BCH_SB_FIELD_journal)
+			continue;
+
+		dst_f = bch2_sb_field_get(dst, src_f->type);
+		dst_f = __bch2_sb_field_resize(dst, dst_f,
+				le32_to_cpu(src_f->u64s));
+
+		memcpy(dst_f, src_f, vstruct_bytes(src_f));
+	}
+}
+
+int bch2_sb_to_fs(struct bch_fs *c, struct bch_sb *src)
+{
+	struct bch_sb_field_journal *journal_buckets =
+		bch2_sb_get_journal(src);
+	unsigned journal_u64s = journal_buckets
+		? le32_to_cpu(journal_buckets->field.u64s)
+		: 0;
+
+	lockdep_assert_held(&c->sb_lock);
+
+	if (bch2_fs_sb_realloc(c, le32_to_cpu(src->u64s) - journal_u64s))
+		return -ENOMEM;
+
+	__copy_super(c->disk_sb, src);
+	bch2_sb_update(c);
+
+	return 0;
+}
+
+int bch2_sb_from_fs(struct bch_fs *c, struct bch_dev *ca)
+{
+	struct bch_sb *src = c->disk_sb, *dst = ca->disk_sb.sb;
+	struct bch_sb_field_journal *journal_buckets =
+		bch2_sb_get_journal(dst);
+	unsigned journal_u64s = journal_buckets
+		? le32_to_cpu(journal_buckets->field.u64s)
+		: 0;
+	unsigned u64s = le32_to_cpu(src->u64s) + journal_u64s;
+	int ret;
+
+	ret = bch2_sb_realloc(&ca->disk_sb, u64s);
+	if (ret)
+		return ret;
+
+	__copy_super(dst, src);
+
+	return 0;
+}
+
+/* read superblock: */
+
+static const char *read_one_super(struct bcache_superblock *sb, u64 offset)
+{
+	struct bch_csum csum;
+	size_t bytes;
+	unsigned order;
+reread:
+	bio_reset(sb->bio);
+	sb->bio->bi_bdev = sb->bdev;
+	sb->bio->bi_iter.bi_sector = offset;
+	sb->bio->bi_iter.bi_size = PAGE_SIZE << sb->page_order;
+	bio_set_op_attrs(sb->bio, REQ_OP_READ, REQ_SYNC|REQ_META);
+	bch2_bio_map(sb->bio, sb->sb);
+
+	if (submit_bio_wait(sb->bio))
+		return "IO error";
+
+	if (uuid_le_cmp(sb->sb->magic, BCACHE_MAGIC))
+		return "Not a bcachefs superblock";
+
+	if (le64_to_cpu(sb->sb->version) != BCACHE_SB_VERSION_CDEV_V4)
+		return "Unsupported superblock version";
+
+	bytes = vstruct_bytes(sb->sb);
+
+	if (bytes > 512 << sb->sb->layout.sb_max_size_bits)
+		return "Bad superblock: too big";
+
+	order = get_order(bytes);
+	if (order > sb->page_order) {
+		if (__bch2_super_realloc(sb, order))
+			return "cannot allocate memory";
+		goto reread;
+	}
+
+	if (BCH_SB_CSUM_TYPE(sb->sb) >= BCH_CSUM_NR)
+		return "unknown csum type";
+
+	/* XXX: verify MACs */
+	csum = csum_vstruct(NULL, BCH_SB_CSUM_TYPE(sb->sb),
+			    (struct nonce) { 0 }, sb->sb);
+
+	if (bch2_crc_cmp(csum, sb->sb->csum))
+		return "bad checksum reading superblock";
+
+	return NULL;
+}
+
+const char *bch2_read_super(struct bcache_superblock *sb,
+			   struct bch_opts opts,
+			   const char *path)
+{
+	u64 offset = opt_defined(opts.sb) ? opts.sb : BCH_SB_SECTOR;
+	struct bch_sb_layout layout;
+	const char *err;
+	unsigned i;
+
+	memset(sb, 0, sizeof(*sb));
+	sb->mode = FMODE_READ;
+
+	if (!(opt_defined(opts.noexcl) && opts.noexcl))
+		sb->mode |= FMODE_EXCL;
+
+	if (!(opt_defined(opts.nochanges) && opts.nochanges))
+		sb->mode |= FMODE_WRITE;
+
+	err = bch2_blkdev_open(path, sb->mode, sb, &sb->bdev);
+	if (err)
+		return err;
+
+	err = "cannot allocate memory";
+	if (__bch2_super_realloc(sb, 0))
+		goto err;
+
+	err = "dynamic fault";
+	if (bch2_fs_init_fault("read_super"))
+		goto err;
+
+	err = read_one_super(sb, offset);
+	if (!err)
+		goto got_super;
+
+	if (offset != BCH_SB_SECTOR) {
+		pr_err("error reading superblock: %s", err);
+		goto err;
+	}
+
+	pr_err("error reading default superblock: %s", err);
+
+	/*
+	 * Error reading primary superblock - read location of backup
+	 * superblocks:
+	 */
+	bio_reset(sb->bio);
+	sb->bio->bi_bdev = sb->bdev;
+	sb->bio->bi_iter.bi_sector = BCH_SB_LAYOUT_SECTOR;
+	sb->bio->bi_iter.bi_size = sizeof(struct bch_sb_layout);
+	bio_set_op_attrs(sb->bio, REQ_OP_READ, REQ_SYNC|REQ_META);
+	/*
+	 * use sb buffer to read layout, since sb buffer is page aligned but
+	 * layout won't be:
+	 */
+	bch2_bio_map(sb->bio, sb->sb);
+
+	err = "IO error";
+	if (submit_bio_wait(sb->bio))
+		goto err;
+
+	memcpy(&layout, sb->sb, sizeof(layout));
+	err = validate_sb_layout(&layout);
+	if (err)
+		goto err;
+
+	for (i = 0; i < layout.nr_superblocks; i++) {
+		u64 offset = le64_to_cpu(layout.sb_offset[i]);
+
+		if (offset == BCH_SB_SECTOR)
+			continue;
+
+		err = read_one_super(sb, offset);
+		if (!err)
+			goto got_super;
+	}
+	goto err;
+got_super:
+	pr_debug("read sb version %llu, flags %llu, seq %llu, journal size %u",
+		 le64_to_cpu(sb->sb->version),
+		 le64_to_cpu(sb->sb->flags),
+		 le64_to_cpu(sb->sb->seq),
+		 le16_to_cpu(sb->sb->u64s));
+
+	err = "Superblock block size smaller than device block size";
+	if (le16_to_cpu(sb->sb->block_size) << 9 <
+	    bdev_logical_block_size(sb->bdev))
+		goto err;
+
+	return NULL;
+err:
+	bch2_free_super(sb);
+	return err;
+}
+
+/* write superblock: */
+
+static void write_super_endio(struct bio *bio)
+{
+	struct bch_dev *ca = bio->bi_private;
+
+	/* XXX: return errors directly */
+
+	bch2_dev_fatal_io_err_on(bio->bi_error, ca, "superblock write");
+
+	closure_put(&ca->fs->sb_write);
+	percpu_ref_put(&ca->io_ref);
+}
+
+static bool write_one_super(struct bch_fs *c, struct bch_dev *ca, unsigned idx)
+{
+	struct bch_sb *sb = ca->disk_sb.sb;
+	struct bio *bio = ca->disk_sb.bio;
+
+	if (idx >= sb->layout.nr_superblocks)
+		return false;
+
+	if (!percpu_ref_tryget(&ca->io_ref))
+		return false;
+
+	sb->offset = sb->layout.sb_offset[idx];
+
+	SET_BCH_SB_CSUM_TYPE(sb, c->opts.metadata_checksum);
+	sb->csum = csum_vstruct(c, BCH_SB_CSUM_TYPE(sb),
+				(struct nonce) { 0 }, sb);
+
+	bio_reset(bio);
+	bio->bi_bdev		= ca->disk_sb.bdev;
+	bio->bi_iter.bi_sector	= le64_to_cpu(sb->offset);
+	bio->bi_iter.bi_size	=
+		roundup(vstruct_bytes(sb),
+			bdev_logical_block_size(ca->disk_sb.bdev));
+	bio->bi_end_io		= write_super_endio;
+	bio->bi_private		= ca;
+	bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_SYNC|REQ_META);
+	bch2_bio_map(bio, sb);
+
+	closure_bio_submit(bio, &c->sb_write);
+	return true;
+}
+
+void bch2_write_super(struct bch_fs *c)
+{
+	struct closure *cl = &c->sb_write;
+	struct bch_dev *ca;
+	unsigned i, super_idx = 0;
+	bool wrote;
+
+	lockdep_assert_held(&c->sb_lock);
+
+	closure_init_stack(cl);
+
+	le64_add_cpu(&c->disk_sb->seq, 1);
+
+	for_each_online_member(ca, c, i)
+		bch2_sb_from_fs(c, ca);
+
+	if (c->opts.nochanges)
+		goto out;
+
+	do {
+		wrote = false;
+		for_each_online_member(ca, c, i)
+			if (write_one_super(c, ca, super_idx))
+				wrote = true;
+
+		closure_sync(cl);
+		super_idx++;
+	} while (wrote);
+out:
+	/* Make new options visible after they're persistent: */
+	bch2_sb_update(c);
+}
+
+void bch2_check_mark_super_slowpath(struct bch_fs *c, const struct bkey_i *k,
+				   bool meta)
+{
+	struct bch_member *mi;
+	struct bkey_s_c_extent e = bkey_i_to_s_c_extent(k);
+	const struct bch_extent_ptr *ptr;
+	unsigned nr_replicas = 0;
+
+	mutex_lock(&c->sb_lock);
+
+	/* recheck, might have raced */
+	if (bch2_check_super_marked(c, k, meta)) {
+		mutex_unlock(&c->sb_lock);
+		return;
+	}
+
+	mi = bch2_sb_get_members(c->disk_sb)->members;
+
+	extent_for_each_ptr(e, ptr)
+		if (!ptr->cached) {
+			(meta
+			 ? SET_BCH_MEMBER_HAS_METADATA
+			 : SET_BCH_MEMBER_HAS_DATA)(mi + ptr->dev, true);
+			nr_replicas++;
+		}
+
+	nr_replicas = min_t(unsigned, nr_replicas,
+			    (meta
+			     ? BCH_SB_META_REPLICAS_HAVE
+			     : BCH_SB_DATA_REPLICAS_HAVE)(c->disk_sb));
+	(meta
+	 ? SET_BCH_SB_META_REPLICAS_HAVE
+	 : SET_BCH_SB_DATA_REPLICAS_HAVE)(c->disk_sb, nr_replicas);
+
+	bch2_write_super(c);
+	mutex_unlock(&c->sb_lock);
+}