Adding upstream version 6.7.7.upstream/6.7.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1967 insertions, 0 deletions

diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
new file mode 100644
index 0000000000..6ab756a485
--- /dev/null
+++ b/fs/bcachefs/journal_io.c
@@ -0,0 +1,1967 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "bcachefs.h"
+#include "alloc_background.h"
+#include "alloc_foreground.h"
+#include "btree_io.h"
+#include "btree_update_interior.h"
+#include "buckets.h"
+#include "checksum.h"
+#include "disk_groups.h"
+#include "error.h"
+#include "journal.h"
+#include "journal_io.h"
+#include "journal_reclaim.h"
+#include "journal_seq_blacklist.h"
+#include "replicas.h"
+#include "sb-clean.h"
+#include "trace.h"
+
+static struct nonce journal_nonce(const struct jset *jset)
+{
+	return (struct nonce) {{
+		[0] = 0,
+		[1] = ((__le32 *) &jset->seq)[0],
+		[2] = ((__le32 *) &jset->seq)[1],
+		[3] = BCH_NONCE_JOURNAL,
+	}};
+}
+
+static bool jset_csum_good(struct bch_fs *c, struct jset *j)
+{
+	return bch2_checksum_type_valid(c, JSET_CSUM_TYPE(j)) &&
+		!bch2_crc_cmp(j->csum,
+			      csum_vstruct(c, JSET_CSUM_TYPE(j), journal_nonce(j), j));
+}
+
+static inline u32 journal_entry_radix_idx(struct bch_fs *c, u64 seq)
+{
+	return (seq - c->journal_entries_base_seq) & (~0U >> 1);
+}
+
+static void __journal_replay_free(struct bch_fs *c,
+				  struct journal_replay *i)
+{
+	struct journal_replay **p =
+		genradix_ptr(&c->journal_entries,
+			     journal_entry_radix_idx(c, le64_to_cpu(i->j.seq)));
+
+	BUG_ON(*p != i);
+	*p = NULL;
+	kvpfree(i, offsetof(struct journal_replay, j) +
+		vstruct_bytes(&i->j));
+}
+
+static void journal_replay_free(struct bch_fs *c, struct journal_replay *i)
+{
+	i->ignore = true;
+
+	if (!c->opts.read_entire_journal)
+		__journal_replay_free(c, i);
+}
+
+struct journal_list {
+	struct closure		cl;
+	u64			last_seq;
+	struct mutex		lock;
+	int			ret;
+};
+
+#define JOURNAL_ENTRY_ADD_OK		0
+#define JOURNAL_ENTRY_ADD_OUT_OF_RANGE	5
+
+/*
+ * Given a journal entry we just read, add it to the list of journal entries to
+ * be replayed:
+ */
+static int journal_entry_add(struct bch_fs *c, struct bch_dev *ca,
+			     struct journal_ptr entry_ptr,
+			     struct journal_list *jlist, struct jset *j)
+{
+	struct genradix_iter iter;
+	struct journal_replay **_i, *i, *dup;
+	struct journal_ptr *ptr;
+	size_t bytes = vstruct_bytes(j);
+	u64 last_seq = !JSET_NO_FLUSH(j) ? le64_to_cpu(j->last_seq) : 0;
+	int ret = JOURNAL_ENTRY_ADD_OK;
+
+	/* Is this entry older than the range we need? */
+	if (!c->opts.read_entire_journal &&
+	    le64_to_cpu(j->seq) < jlist->last_seq)
+		return JOURNAL_ENTRY_ADD_OUT_OF_RANGE;
+
+	/*
+	 * genradixes are indexed by a ulong, not a u64, so we can't index them
+	 * by sequence number directly: Assume instead that they will all fall
+	 * within the range of +-2billion of the filrst one we find.
+	 */
+	if (!c->journal_entries_base_seq)
+		c->journal_entries_base_seq = max_t(s64, 1, le64_to_cpu(j->seq) - S32_MAX);
+
+	/* Drop entries we don't need anymore */
+	if (last_seq > jlist->last_seq && !c->opts.read_entire_journal) {
+		genradix_for_each_from(&c->journal_entries, iter, _i,
+				       journal_entry_radix_idx(c, jlist->last_seq)) {
+			i = *_i;
+
+			if (!i || i->ignore)
+				continue;
+
+			if (le64_to_cpu(i->j.seq) >= last_seq)
+				break;
+			journal_replay_free(c, i);
+		}
+	}
+
+	jlist->last_seq = max(jlist->last_seq, last_seq);
+
+	_i = genradix_ptr_alloc(&c->journal_entries,
+				journal_entry_radix_idx(c, le64_to_cpu(j->seq)),
+				GFP_KERNEL);
+	if (!_i)
+		return -BCH_ERR_ENOMEM_journal_entry_add;
+
+	/*
+	 * Duplicate journal entries? If so we want the one that didn't have a
+	 * checksum error:
+	 */
+	dup = *_i;
+	if (dup) {
+		if (bytes == vstruct_bytes(&dup->j) &&
+		    !memcmp(j, &dup->j, bytes)) {
+			i = dup;
+			goto found;
+		}
+
+		if (!entry_ptr.csum_good) {
+			i = dup;
+			goto found;
+		}
+
+		if (!dup->csum_good)
+			goto replace;
+
+		fsck_err(c, journal_entry_replicas_data_mismatch,
+			 "found duplicate but non identical journal entries (seq %llu)",
+			 le64_to_cpu(j->seq));
+		i = dup;
+		goto found;
+	}
+replace:
+	i = kvpmalloc(offsetof(struct journal_replay, j) + bytes, GFP_KERNEL);
+	if (!i)
+		return -BCH_ERR_ENOMEM_journal_entry_add;
+
+	i->nr_ptrs	= 0;
+	i->csum_good	= entry_ptr.csum_good;
+	i->ignore	= false;
+	unsafe_memcpy(&i->j, j, bytes, "embedded variable length struct");
+	i->ptrs[i->nr_ptrs++] = entry_ptr;
+
+	if (dup) {
+		if (dup->nr_ptrs >= ARRAY_SIZE(dup->ptrs)) {
+			bch_err(c, "found too many copies of journal entry %llu",
+				le64_to_cpu(i->j.seq));
+			dup->nr_ptrs = ARRAY_SIZE(dup->ptrs) - 1;
+		}
+
+		/* The first ptr should represent the jset we kept: */
+		memcpy(i->ptrs + i->nr_ptrs,
+		       dup->ptrs,
+		       sizeof(dup->ptrs[0]) * dup->nr_ptrs);
+		i->nr_ptrs += dup->nr_ptrs;
+		__journal_replay_free(c, dup);
+	}
+
+	*_i = i;
+	return 0;
+found:
+	for (ptr = i->ptrs; ptr < i->ptrs + i->nr_ptrs; ptr++) {
+		if (ptr->dev == ca->dev_idx) {
+			bch_err(c, "duplicate journal entry %llu on same device",
+				le64_to_cpu(i->j.seq));
+			goto out;
+		}
+	}
+
+	if (i->nr_ptrs >= ARRAY_SIZE(i->ptrs)) {
+		bch_err(c, "found too many copies of journal entry %llu",
+			le64_to_cpu(i->j.seq));
+		goto out;
+	}
+
+	i->ptrs[i->nr_ptrs++] = entry_ptr;
+out:
+fsck_err:
+	return ret;
+}
+
+/* this fills in a range with empty jset_entries: */
+static void journal_entry_null_range(void *start, void *end)
+{
+	struct jset_entry *entry;
+
+	for (entry = start; entry != end; entry = vstruct_next(entry))
+		memset(entry, 0, sizeof(*entry));
+}
+
+#define JOURNAL_ENTRY_REREAD	5
+#define JOURNAL_ENTRY_NONE	6
+#define JOURNAL_ENTRY_BAD	7
+
+static void journal_entry_err_msg(struct printbuf *out,
+				  u32 version,
+				  struct jset *jset,
+				  struct jset_entry *entry)
+{
+	prt_str(out, "invalid journal entry, version=");
+	bch2_version_to_text(out, version);
+
+	if (entry) {
+		prt_str(out, " type=");
+		prt_str(out, bch2_jset_entry_types[entry->type]);
+	}
+
+	if (!jset) {
+		prt_printf(out, " in superblock");
+	} else {
+
+		prt_printf(out, " seq=%llu", le64_to_cpu(jset->seq));
+
+		if (entry)
+			prt_printf(out, " offset=%zi/%u",
+				   (u64 *) entry - jset->_data,
+				   le32_to_cpu(jset->u64s));
+	}
+
+	prt_str(out, ": ");
+}
+
+#define journal_entry_err(c, version, jset, entry, _err, msg, ...)	\
+({									\
+	struct printbuf _buf = PRINTBUF;				\
+									\
+	journal_entry_err_msg(&_buf, version, jset, entry);		\
+	prt_printf(&_buf, msg, ##__VA_ARGS__);				\
+									\
+	switch (flags & BKEY_INVALID_WRITE) {				\
+	case READ:							\
+		mustfix_fsck_err(c, _err, "%s", _buf.buf);		\
+		break;							\
+	case WRITE:							\
+		bch2_sb_error_count(c, BCH_FSCK_ERR_##_err);		\
+		bch_err(c, "corrupt metadata before write: %s\n", _buf.buf);\
+		if (bch2_fs_inconsistent(c)) {				\
+			ret = -BCH_ERR_fsck_errors_not_fixed;		\
+			goto fsck_err;					\
+		}							\
+		break;							\
+	}								\
+									\
+	printbuf_exit(&_buf);						\
+	true;								\
+})
+
+#define journal_entry_err_on(cond, ...)					\
+	((cond) ? journal_entry_err(__VA_ARGS__) : false)
+
+#define FSCK_DELETED_KEY	5
+
+static int journal_validate_key(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned level, enum btree_id btree_id,
+				struct bkey_i *k,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	int write = flags & BKEY_INVALID_WRITE;
+	void *next = vstruct_next(entry);
+	struct printbuf buf = PRINTBUF;
+	int ret = 0;
+
+	if (journal_entry_err_on(!k->k.u64s,
+				 c, version, jset, entry,
+				 journal_entry_bkey_u64s_0,
+				 "k->u64s 0")) {
+		entry->u64s = cpu_to_le16((u64 *) k - entry->_data);
+		journal_entry_null_range(vstruct_next(entry), next);
+		return FSCK_DELETED_KEY;
+	}
+
+	if (journal_entry_err_on((void *) bkey_next(k) >
+				 (void *) vstruct_next(entry),
+				 c, version, jset, entry,
+				 journal_entry_bkey_past_end,
+				 "extends past end of journal entry")) {
+		entry->u64s = cpu_to_le16((u64 *) k - entry->_data);
+		journal_entry_null_range(vstruct_next(entry), next);
+		return FSCK_DELETED_KEY;
+	}
+
+	if (journal_entry_err_on(k->k.format != KEY_FORMAT_CURRENT,
+				 c, version, jset, entry,
+				 journal_entry_bkey_bad_format,
+				 "bad format %u", k->k.format)) {
+		le16_add_cpu(&entry->u64s, -((u16) k->k.u64s));
+		memmove(k, bkey_next(k), next - (void *) bkey_next(k));
+		journal_entry_null_range(vstruct_next(entry), next);
+		return FSCK_DELETED_KEY;
+	}
+
+	if (!write)
+		bch2_bkey_compat(level, btree_id, version, big_endian,
+				 write, NULL, bkey_to_packed(k));
+
+	if (bch2_bkey_invalid(c, bkey_i_to_s_c(k),
+			      __btree_node_type(level, btree_id), write, &buf)) {
+		printbuf_reset(&buf);
+		journal_entry_err_msg(&buf, version, jset, entry);
+		prt_newline(&buf);
+		printbuf_indent_add(&buf, 2);
+
+		bch2_bkey_val_to_text(&buf, c, bkey_i_to_s_c(k));
+		prt_newline(&buf);
+		bch2_bkey_invalid(c, bkey_i_to_s_c(k),
+				  __btree_node_type(level, btree_id), write, &buf);
+
+		mustfix_fsck_err(c, journal_entry_bkey_invalid,
+				 "%s", buf.buf);
+
+		le16_add_cpu(&entry->u64s, -((u16) k->k.u64s));
+		memmove(k, bkey_next(k), next - (void *) bkey_next(k));
+		journal_entry_null_range(vstruct_next(entry), next);
+
+		printbuf_exit(&buf);
+		return FSCK_DELETED_KEY;
+	}
+
+	if (write)
+		bch2_bkey_compat(level, btree_id, version, big_endian,
+				 write, NULL, bkey_to_packed(k));
+fsck_err:
+	printbuf_exit(&buf);
+	return ret;
+}
+
+static int journal_entry_btree_keys_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct bkey_i *k = entry->start;
+
+	while (k != vstruct_last(entry)) {
+		int ret = journal_validate_key(c, jset, entry,
+					       entry->level,
+					       entry->btree_id,
+					       k, version, big_endian,
+					       flags|BKEY_INVALID_JOURNAL);
+		if (ret == FSCK_DELETED_KEY)
+			continue;
+
+		k = bkey_next(k);
+	}
+
+	return 0;
+}
+
+static void journal_entry_btree_keys_to_text(struct printbuf *out, struct bch_fs *c,
+					     struct jset_entry *entry)
+{
+	struct bkey_i *k;
+	bool first = true;
+
+	jset_entry_for_each_key(entry, k) {
+		if (!first) {
+			prt_newline(out);
+			prt_printf(out, "%s: ", bch2_jset_entry_types[entry->type]);
+		}
+		prt_printf(out, "btree=%s l=%u ", bch2_btree_id_str(entry->btree_id), entry->level);
+		bch2_bkey_val_to_text(out, c, bkey_i_to_s_c(k));
+		first = false;
+	}
+}
+
+static int journal_entry_btree_root_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct bkey_i *k = entry->start;
+	int ret = 0;
+
+	if (journal_entry_err_on(!entry->u64s ||
+				 le16_to_cpu(entry->u64s) != k->k.u64s,
+				 c, version, jset, entry,
+				 journal_entry_btree_root_bad_size,
+				 "invalid btree root journal entry: wrong number of keys")) {
+		void *next = vstruct_next(entry);
+		/*
+		 * we don't want to null out this jset_entry,
+		 * just the contents, so that later we can tell
+		 * we were _supposed_ to have a btree root
+		 */
+		entry->u64s = 0;
+		journal_entry_null_range(vstruct_next(entry), next);
+		return 0;
+	}
+
+	ret = journal_validate_key(c, jset, entry, 1, entry->btree_id, k,
+				   version, big_endian, flags);
+	if (ret == FSCK_DELETED_KEY)
+		ret = 0;
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_btree_root_to_text(struct printbuf *out, struct bch_fs *c,
+					     struct jset_entry *entry)
+{
+	journal_entry_btree_keys_to_text(out, c, entry);
+}
+
+static int journal_entry_prio_ptrs_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	/* obsolete, don't care: */
+	return 0;
+}
+
+static void journal_entry_prio_ptrs_to_text(struct printbuf *out, struct bch_fs *c,
+					    struct jset_entry *entry)
+{
+}
+
+static int journal_entry_blacklist_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	int ret = 0;
+
+	if (journal_entry_err_on(le16_to_cpu(entry->u64s) != 1,
+				 c, version, jset, entry,
+				 journal_entry_blacklist_bad_size,
+		"invalid journal seq blacklist entry: bad size")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+	}
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_blacklist_to_text(struct printbuf *out, struct bch_fs *c,
+					    struct jset_entry *entry)
+{
+	struct jset_entry_blacklist *bl =
+		container_of(entry, struct jset_entry_blacklist, entry);
+
+	prt_printf(out, "seq=%llu", le64_to_cpu(bl->seq));
+}
+
+static int journal_entry_blacklist_v2_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct jset_entry_blacklist_v2 *bl_entry;
+	int ret = 0;
+
+	if (journal_entry_err_on(le16_to_cpu(entry->u64s) != 2,
+				 c, version, jset, entry,
+				 journal_entry_blacklist_v2_bad_size,
+		"invalid journal seq blacklist entry: bad size")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		goto out;
+	}
+
+	bl_entry = container_of(entry, struct jset_entry_blacklist_v2, entry);
+
+	if (journal_entry_err_on(le64_to_cpu(bl_entry->start) >
+				 le64_to_cpu(bl_entry->end),
+				 c, version, jset, entry,
+				 journal_entry_blacklist_v2_start_past_end,
+		"invalid journal seq blacklist entry: start > end")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+	}
+out:
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_blacklist_v2_to_text(struct printbuf *out, struct bch_fs *c,
+					       struct jset_entry *entry)
+{
+	struct jset_entry_blacklist_v2 *bl =
+		container_of(entry, struct jset_entry_blacklist_v2, entry);
+
+	prt_printf(out, "start=%llu end=%llu",
+	       le64_to_cpu(bl->start),
+	       le64_to_cpu(bl->end));
+}
+
+static int journal_entry_usage_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct jset_entry_usage *u =
+		container_of(entry, struct jset_entry_usage, entry);
+	unsigned bytes = jset_u64s(le16_to_cpu(entry->u64s)) * sizeof(u64);
+	int ret = 0;
+
+	if (journal_entry_err_on(bytes < sizeof(*u),
+				 c, version, jset, entry,
+				 journal_entry_usage_bad_size,
+				 "invalid journal entry usage: bad size")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_usage_to_text(struct printbuf *out, struct bch_fs *c,
+					struct jset_entry *entry)
+{
+	struct jset_entry_usage *u =
+		container_of(entry, struct jset_entry_usage, entry);
+
+	prt_printf(out, "type=%s v=%llu",
+	       bch2_fs_usage_types[u->entry.btree_id],
+	       le64_to_cpu(u->v));
+}
+
+static int journal_entry_data_usage_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct jset_entry_data_usage *u =
+		container_of(entry, struct jset_entry_data_usage, entry);
+	unsigned bytes = jset_u64s(le16_to_cpu(entry->u64s)) * sizeof(u64);
+	struct printbuf err = PRINTBUF;
+	int ret = 0;
+
+	if (journal_entry_err_on(bytes < sizeof(*u) ||
+				 bytes < sizeof(*u) + u->r.nr_devs,
+				 c, version, jset, entry,
+				 journal_entry_data_usage_bad_size,
+				 "invalid journal entry usage: bad size")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		goto out;
+	}
+
+	if (journal_entry_err_on(bch2_replicas_entry_validate(&u->r, c->disk_sb.sb, &err),
+				 c, version, jset, entry,
+				 journal_entry_data_usage_bad_size,
+				 "invalid journal entry usage: %s", err.buf)) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		goto out;
+	}
+out:
+fsck_err:
+	printbuf_exit(&err);
+	return ret;
+}
+
+static void journal_entry_data_usage_to_text(struct printbuf *out, struct bch_fs *c,
+					     struct jset_entry *entry)
+{
+	struct jset_entry_data_usage *u =
+		container_of(entry, struct jset_entry_data_usage, entry);
+
+	bch2_replicas_entry_to_text(out, &u->r);
+	prt_printf(out, "=%llu", le64_to_cpu(u->v));
+}
+
+static int journal_entry_clock_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct jset_entry_clock *clock =
+		container_of(entry, struct jset_entry_clock, entry);
+	unsigned bytes = jset_u64s(le16_to_cpu(entry->u64s)) * sizeof(u64);
+	int ret = 0;
+
+	if (journal_entry_err_on(bytes != sizeof(*clock),
+				 c, version, jset, entry,
+				 journal_entry_clock_bad_size,
+				 "bad size")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+	if (journal_entry_err_on(clock->rw > 1,
+				 c, version, jset, entry,
+				 journal_entry_clock_bad_rw,
+				 "bad rw")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_clock_to_text(struct printbuf *out, struct bch_fs *c,
+					struct jset_entry *entry)
+{
+	struct jset_entry_clock *clock =
+		container_of(entry, struct jset_entry_clock, entry);
+
+	prt_printf(out, "%s=%llu", clock->rw ? "write" : "read", le64_to_cpu(clock->time));
+}
+
+static int journal_entry_dev_usage_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	struct jset_entry_dev_usage *u =
+		container_of(entry, struct jset_entry_dev_usage, entry);
+	unsigned bytes = jset_u64s(le16_to_cpu(entry->u64s)) * sizeof(u64);
+	unsigned expected = sizeof(*u);
+	unsigned dev;
+	int ret = 0;
+
+	if (journal_entry_err_on(bytes < expected,
+				 c, version, jset, entry,
+				 journal_entry_dev_usage_bad_size,
+				 "bad size (%u < %u)",
+				 bytes, expected)) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+	dev = le32_to_cpu(u->dev);
+
+	if (journal_entry_err_on(!bch2_dev_exists2(c, dev),
+				 c, version, jset, entry,
+				 journal_entry_dev_usage_bad_dev,
+				 "bad dev")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+	if (journal_entry_err_on(u->pad,
+				 c, version, jset, entry,
+				 journal_entry_dev_usage_bad_pad,
+				 "bad pad")) {
+		journal_entry_null_range(entry, vstruct_next(entry));
+		return ret;
+	}
+
+fsck_err:
+	return ret;
+}
+
+static void journal_entry_dev_usage_to_text(struct printbuf *out, struct bch_fs *c,
+					    struct jset_entry *entry)
+{
+	struct jset_entry_dev_usage *u =
+		container_of(entry, struct jset_entry_dev_usage, entry);
+	unsigned i, nr_types = jset_entry_dev_usage_nr_types(u);
+
+	prt_printf(out, "dev=%u", le32_to_cpu(u->dev));
+
+	for (i = 0; i < nr_types; i++) {
+		if (i < BCH_DATA_NR)
+			prt_printf(out, " %s", bch2_data_types[i]);
+		else
+			prt_printf(out, " (unknown data type %u)", i);
+		prt_printf(out, ": buckets=%llu sectors=%llu fragmented=%llu",
+		       le64_to_cpu(u->d[i].buckets),
+		       le64_to_cpu(u->d[i].sectors),
+		       le64_to_cpu(u->d[i].fragmented));
+	}
+
+	prt_printf(out, " buckets_ec: %llu", le64_to_cpu(u->buckets_ec));
+}
+
+static int journal_entry_log_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	return 0;
+}
+
+static void journal_entry_log_to_text(struct printbuf *out, struct bch_fs *c,
+				      struct jset_entry *entry)
+{
+	struct jset_entry_log *l = container_of(entry, struct jset_entry_log, entry);
+	unsigned bytes = vstruct_bytes(entry) - offsetof(struct jset_entry_log, d);
+
+	prt_printf(out, "%.*s", bytes, l->d);
+}
+
+static int journal_entry_overwrite_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	return journal_entry_btree_keys_validate(c, jset, entry,
+				version, big_endian, READ);
+}
+
+static void journal_entry_overwrite_to_text(struct printbuf *out, struct bch_fs *c,
+					    struct jset_entry *entry)
+{
+	journal_entry_btree_keys_to_text(out, c, entry);
+}
+
+struct jset_entry_ops {
+	int (*validate)(struct bch_fs *, struct jset *,
+			struct jset_entry *, unsigned, int,
+			enum bkey_invalid_flags);
+	void (*to_text)(struct printbuf *, struct bch_fs *, struct jset_entry *);
+};
+
+static const struct jset_entry_ops bch2_jset_entry_ops[] = {
+#define x(f, nr)						\
+	[BCH_JSET_ENTRY_##f]	= (struct jset_entry_ops) {	\
+		.validate	= journal_entry_##f##_validate,	\
+		.to_text	= journal_entry_##f##_to_text,	\
+	},
+	BCH_JSET_ENTRY_TYPES()
+#undef x
+};
+
+int bch2_journal_entry_validate(struct bch_fs *c,
+				struct jset *jset,
+				struct jset_entry *entry,
+				unsigned version, int big_endian,
+				enum bkey_invalid_flags flags)
+{
+	return entry->type < BCH_JSET_ENTRY_NR
+		? bch2_jset_entry_ops[entry->type].validate(c, jset, entry,
+				version, big_endian, flags)
+		: 0;
+}
+
+void bch2_journal_entry_to_text(struct printbuf *out, struct bch_fs *c,
+				struct jset_entry *entry)
+{
+	if (entry->type < BCH_JSET_ENTRY_NR) {
+		prt_printf(out, "%s: ", bch2_jset_entry_types[entry->type]);
+		bch2_jset_entry_ops[entry->type].to_text(out, c, entry);
+	} else {
+		prt_printf(out, "(unknown type %u)", entry->type);
+	}
+}
+
+static int jset_validate_entries(struct bch_fs *c, struct jset *jset,
+				 enum bkey_invalid_flags flags)
+{
+	struct jset_entry *entry;
+	unsigned version = le32_to_cpu(jset->version);
+	int ret = 0;
+
+	vstruct_for_each(jset, entry) {
+		if (journal_entry_err_on(vstruct_next(entry) > vstruct_last(jset),
+				c, version, jset, entry,
+				journal_entry_past_jset_end,
+				"journal entry extends past end of jset")) {
+			jset->u64s = cpu_to_le32((u64 *) entry - jset->_data);
+			break;
+		}
+
+		ret = bch2_journal_entry_validate(c, jset, entry,
+					version, JSET_BIG_ENDIAN(jset), flags);
+		if (ret)
+			break;
+	}
+fsck_err:
+	return ret;
+}
+
+static int jset_validate(struct bch_fs *c,
+			 struct bch_dev *ca,
+			 struct jset *jset, u64 sector,
+			 enum bkey_invalid_flags flags)
+{
+	unsigned version;
+	int ret = 0;
+
+	if (le64_to_cpu(jset->magic) != jset_magic(c))
+		return JOURNAL_ENTRY_NONE;
+
+	version = le32_to_cpu(jset->version);
+	if (journal_entry_err_on(!bch2_version_compatible(version),
+			c, version, jset, NULL,
+			jset_unsupported_version,
+			"%s sector %llu seq %llu: incompatible journal entry version %u.%u",
+			ca ? ca->name : c->name,
+			sector, le64_to_cpu(jset->seq),
+			BCH_VERSION_MAJOR(version),
+			BCH_VERSION_MINOR(version))) {
+		/* don't try to continue: */
+		return -EINVAL;
+	}
+
+	if (journal_entry_err_on(!bch2_checksum_type_valid(c, JSET_CSUM_TYPE(jset)),
+			c, version, jset, NULL,
+			jset_unknown_csum,
+			"%s sector %llu seq %llu: journal entry with unknown csum type %llu",
+			ca ? ca->name : c->name,
+			sector, le64_to_cpu(jset->seq),
+			JSET_CSUM_TYPE(jset)))
+		ret = JOURNAL_ENTRY_BAD;
+
+	/* last_seq is ignored when JSET_NO_FLUSH is true */
+	if (journal_entry_err_on(!JSET_NO_FLUSH(jset) &&
+				 le64_to_cpu(jset->last_seq) > le64_to_cpu(jset->seq),
+				 c, version, jset, NULL,
+				 jset_last_seq_newer_than_seq,
+				 "invalid journal entry: last_seq > seq (%llu > %llu)",
+				 le64_to_cpu(jset->last_seq),
+				 le64_to_cpu(jset->seq))) {
+		jset->last_seq = jset->seq;
+		return JOURNAL_ENTRY_BAD;
+	}
+
+	ret = jset_validate_entries(c, jset, flags);
+fsck_err:
+	return ret;
+}
+
+static int jset_validate_early(struct bch_fs *c,
+			 struct bch_dev *ca,
+			 struct jset *jset, u64 sector,
+			 unsigned bucket_sectors_left,
+			 unsigned sectors_read)
+{
+	size_t bytes = vstruct_bytes(jset);
+	unsigned version;
+	enum bkey_invalid_flags flags = BKEY_INVALID_JOURNAL;
+	int ret = 0;
+
+	if (le64_to_cpu(jset->magic) != jset_magic(c))
+		return JOURNAL_ENTRY_NONE;
+
+	version = le32_to_cpu(jset->version);
+	if (journal_entry_err_on(!bch2_version_compatible(version),
+			c, version, jset, NULL,
+			jset_unsupported_version,
+			"%s sector %llu seq %llu: unknown journal entry version %u.%u",
+			ca ? ca->name : c->name,
+			sector, le64_to_cpu(jset->seq),
+			BCH_VERSION_MAJOR(version),
+			BCH_VERSION_MINOR(version))) {
+		/* don't try to continue: */
+		return -EINVAL;
+	}
+
+	if (bytes > (sectors_read << 9) &&
+	    sectors_read < bucket_sectors_left)
+		return JOURNAL_ENTRY_REREAD;
+
+	if (journal_entry_err_on(bytes > bucket_sectors_left << 9,
+			c, version, jset, NULL,
+			jset_past_bucket_end,
+			"%s sector %llu seq %llu: journal entry too big (%zu bytes)",
+			ca ? ca->name : c->name,
+			sector, le64_to_cpu(jset->seq), bytes))
+		le32_add_cpu(&jset->u64s,
+			     -((bytes - (bucket_sectors_left << 9)) / 8));
+fsck_err:
+	return ret;
+}
+
+struct journal_read_buf {
+	void		*data;
+	size_t		size;
+};
+
+static int journal_read_buf_realloc(struct journal_read_buf *b,
+				    size_t new_size)
+{
+	void *n;
+
+	/* the bios are sized for this many pages, max: */
+	if (new_size > JOURNAL_ENTRY_SIZE_MAX)
+		return -BCH_ERR_ENOMEM_journal_read_buf_realloc;
+
+	new_size = roundup_pow_of_two(new_size);
+	n = kvpmalloc(new_size, GFP_KERNEL);
+	if (!n)
+		return -BCH_ERR_ENOMEM_journal_read_buf_realloc;
+
+	kvpfree(b->data, b->size);
+	b->data = n;
+	b->size = new_size;
+	return 0;
+}
+
+static int journal_read_bucket(struct bch_dev *ca,
+			       struct journal_read_buf *buf,
+			       struct journal_list *jlist,
+			       unsigned bucket)
+{
+	struct bch_fs *c = ca->fs;
+	struct journal_device *ja = &ca->journal;
+	struct jset *j = NULL;
+	unsigned sectors, sectors_read = 0;
+	u64 offset = bucket_to_sector(ca, ja->buckets[bucket]),
+	    end = offset + ca->mi.bucket_size;
+	bool saw_bad = false, csum_good;
+	int ret = 0;
+
+	pr_debug("reading %u", bucket);
+
+	while (offset < end) {
+		if (!sectors_read) {
+			struct bio *bio;
+			unsigned nr_bvecs;
+reread:
+			sectors_read = min_t(unsigned,
+				end - offset, buf->size >> 9);
+			nr_bvecs = buf_pages(buf->data, sectors_read << 9);
+
+			bio = bio_kmalloc(nr_bvecs, GFP_KERNEL);
+			bio_init(bio, ca->disk_sb.bdev, bio->bi_inline_vecs, nr_bvecs, REQ_OP_READ);
+
+			bio->bi_iter.bi_sector = offset;
+			bch2_bio_map(bio, buf->data, sectors_read << 9);
+
+			ret = submit_bio_wait(bio);
+			kfree(bio);
+
+			if (bch2_dev_io_err_on(ret, ca, BCH_MEMBER_ERROR_read,
+					       "journal read error: sector %llu",
+					       offset) ||
+			    bch2_meta_read_fault("journal")) {
+				/*
+				 * We don't error out of the recovery process
+				 * here, since the relevant journal entry may be
+				 * found on a different device, and missing or
+				 * no journal entries will be handled later
+				 */
+				return 0;
+			}
+
+			j = buf->data;
+		}
+
+		ret = jset_validate_early(c, ca, j, offset,
+				    end - offset, sectors_read);
+		switch (ret) {
+		case 0:
+			sectors = vstruct_sectors(j, c->block_bits);
+			break;
+		case JOURNAL_ENTRY_REREAD:
+			if (vstruct_bytes(j) > buf->size) {
+				ret = journal_read_buf_realloc(buf,
+							vstruct_bytes(j));
+				if (ret)
+					return ret;
+			}
+			goto reread;
+		case JOURNAL_ENTRY_NONE:
+			if (!saw_bad)
+				return 0;
+			/*
+			 * On checksum error we don't really trust the size
+			 * field of the journal entry we read, so try reading
+			 * again at next block boundary:
+			 */
+			sectors = block_sectors(c);
+			goto next_block;
+		default:
+			return ret;
+		}
+
+		/*
+		 * This happens sometimes if we don't have discards on -
+		 * when we've partially overwritten a bucket with new
+		 * journal entries. We don't need the rest of the
+		 * bucket:
+		 */
+		if (le64_to_cpu(j->seq) < ja->bucket_seq[bucket])
+			return 0;
+
+		ja->bucket_seq[bucket] = le64_to_cpu(j->seq);
+
+		csum_good = jset_csum_good(c, j);
+		if (bch2_dev_io_err_on(!csum_good, ca, BCH_MEMBER_ERROR_checksum,
+				       "journal checksum error"))
+			saw_bad = true;
+
+		ret = bch2_encrypt(c, JSET_CSUM_TYPE(j), journal_nonce(j),
+			     j->encrypted_start,
+			     vstruct_end(j) - (void *) j->encrypted_start);
+		bch2_fs_fatal_err_on(ret, c,
+				"error decrypting journal entry: %i", ret);
+
+		mutex_lock(&jlist->lock);
+		ret = journal_entry_add(c, ca, (struct journal_ptr) {
+					.csum_good	= csum_good,
+					.dev		= ca->dev_idx,
+					.bucket		= bucket,
+					.bucket_offset	= offset -
+						bucket_to_sector(ca, ja->buckets[bucket]),
+					.sector		= offset,
+					}, jlist, j);
+		mutex_unlock(&jlist->lock);
+
+		switch (ret) {
+		case JOURNAL_ENTRY_ADD_OK:
+			break;
+		case JOURNAL_ENTRY_ADD_OUT_OF_RANGE:
+			break;
+		default:
+			return ret;
+		}
+next_block:
+		pr_debug("next");
+		offset		+= sectors;
+		sectors_read	-= sectors;
+		j = ((void *) j) + (sectors << 9);
+	}
+
+	return 0;
+}
+
+static CLOSURE_CALLBACK(bch2_journal_read_device)
+{
+	closure_type(ja, struct journal_device, read);
+	struct bch_dev *ca = container_of(ja, struct bch_dev, journal);
+	struct bch_fs *c = ca->fs;
+	struct journal_list *jlist =
+		container_of(cl->parent, struct journal_list, cl);
+	struct journal_replay *r, **_r;
+	struct genradix_iter iter;
+	struct journal_read_buf buf = { NULL, 0 };
+	unsigned i;
+	int ret = 0;
+
+	if (!ja->nr)
+		goto out;
+
+	ret = journal_read_buf_realloc(&buf, PAGE_SIZE);
+	if (ret)
+		goto err;
+
+	pr_debug("%u journal buckets", ja->nr);
+
+	for (i = 0; i < ja->nr; i++) {
+		ret = journal_read_bucket(ca, &buf, jlist, i);
+		if (ret)
+			goto err;
+	}
+
+	ja->sectors_free = ca->mi.bucket_size;
+
+	mutex_lock(&jlist->lock);
+	genradix_for_each_reverse(&c->journal_entries, iter, _r) {
+		r = *_r;
+
+		if (!r)
+			continue;
+
+		for (i = 0; i < r->nr_ptrs; i++) {
+			if (r->ptrs[i].dev == ca->dev_idx) {
+				unsigned wrote = bucket_remainder(ca, r->ptrs[i].sector) +
+					vstruct_sectors(&r->j, c->block_bits);
+
+				ja->cur_idx = r->ptrs[i].bucket;
+				ja->sectors_free = ca->mi.bucket_size - wrote;
+				goto found;
+			}
+		}
+	}
+found:
+	mutex_unlock(&jlist->lock);
+
+	if (ja->bucket_seq[ja->cur_idx] &&
+	    ja->sectors_free == ca->mi.bucket_size) {
+#if 0
+		/*
+		 * Debug code for ZNS support, where we (probably) want to be
+		 * correlated where we stopped in the journal to the zone write
+		 * points:
+		 */
+		bch_err(c, "ja->sectors_free == ca->mi.bucket_size");
+		bch_err(c, "cur_idx %u/%u", ja->cur_idx, ja->nr);
+		for (i = 0; i < 3; i++) {
+			unsigned idx = (ja->cur_idx + ja->nr - 1 + i) % ja->nr;
+
+			bch_err(c, "bucket_seq[%u] = %llu", idx, ja->bucket_seq[idx]);
+		}
+#endif
+		ja->sectors_free = 0;
+	}
+
+	/*
+	 * Set dirty_idx to indicate the entire journal is full and needs to be
+	 * reclaimed - journal reclaim will immediately reclaim whatever isn't
+	 * pinned when it first runs:
+	 */
+	ja->discard_idx = ja->dirty_idx_ondisk =
+		ja->dirty_idx = (ja->cur_idx + 1) % ja->nr;
+out:
+	bch_verbose(c, "journal read done on device %s, ret %i", ca->name, ret);
+	kvpfree(buf.data, buf.size);
+	percpu_ref_put(&ca->io_ref);
+	closure_return(cl);
+	return;
+err:
+	mutex_lock(&jlist->lock);
+	jlist->ret = ret;
+	mutex_unlock(&jlist->lock);
+	goto out;
+}
+
+void bch2_journal_ptrs_to_text(struct printbuf *out, struct bch_fs *c,
+			       struct journal_replay *j)
+{
+	unsigned i;
+
+	for (i = 0; i < j->nr_ptrs; i++) {
+		struct bch_dev *ca = bch_dev_bkey_exists(c, j->ptrs[i].dev);
+		u64 offset;
+
+		div64_u64_rem(j->ptrs[i].sector, ca->mi.bucket_size, &offset);
+
+		if (i)
+			prt_printf(out, " ");
+		prt_printf(out, "%u:%u:%u (sector %llu)",
+		       j->ptrs[i].dev,
+		       j->ptrs[i].bucket,
+		       j->ptrs[i].bucket_offset,
+		       j->ptrs[i].sector);
+	}
+}
+
+int bch2_journal_read(struct bch_fs *c,
+		      u64 *last_seq,
+		      u64 *blacklist_seq,
+		      u64 *start_seq)
+{
+	struct journal_list jlist;
+	struct journal_replay *i, **_i, *prev = NULL;
+	struct genradix_iter radix_iter;
+	struct bch_dev *ca;
+	unsigned iter;
+	struct printbuf buf = PRINTBUF;
+	bool degraded = false, last_write_torn = false;
+	u64 seq;
+	int ret = 0;
+
+	closure_init_stack(&jlist.cl);
+	mutex_init(&jlist.lock);
+	jlist.last_seq = 0;
+	jlist.ret = 0;
+
+	for_each_member_device(ca, c, iter) {
+		if (!c->opts.fsck &&
+		    !(bch2_dev_has_data(c, ca) & (1 << BCH_DATA_journal)))
+			continue;
+
+		if ((ca->mi.state == BCH_MEMBER_STATE_rw ||
+		     ca->mi.state == BCH_MEMBER_STATE_ro) &&
+		    percpu_ref_tryget(&ca->io_ref))
+			closure_call(&ca->journal.read,
+				     bch2_journal_read_device,
+				     system_unbound_wq,
+				     &jlist.cl);
+		else
+			degraded = true;
+	}
+
+	closure_sync(&jlist.cl);
+
+	if (jlist.ret)
+		return jlist.ret;
+
+	*last_seq	= 0;
+	*start_seq	= 0;
+	*blacklist_seq	= 0;
+
+	/*
+	 * Find most recent flush entry, and ignore newer non flush entries -
+	 * those entries will be blacklisted:
+	 */
+	genradix_for_each_reverse(&c->journal_entries, radix_iter, _i) {
+		enum bkey_invalid_flags flags = BKEY_INVALID_JOURNAL;
+
+		i = *_i;
+
+		if (!i || i->ignore)
+			continue;
+
+		if (!*start_seq)
+			*blacklist_seq = *start_seq = le64_to_cpu(i->j.seq) + 1;
+
+		if (JSET_NO_FLUSH(&i->j)) {
+			i->ignore = true;
+			continue;
+		}
+
+		if (!last_write_torn && !i->csum_good) {
+			last_write_torn = true;
+			i->ignore = true;
+			continue;
+		}
+
+		if (journal_entry_err_on(le64_to_cpu(i->j.last_seq) > le64_to_cpu(i->j.seq),
+					 c, le32_to_cpu(i->j.version), &i->j, NULL,
+					 jset_last_seq_newer_than_seq,
+					 "invalid journal entry: last_seq > seq (%llu > %llu)",
+					 le64_to_cpu(i->j.last_seq),
+					 le64_to_cpu(i->j.seq)))
+			i->j.last_seq = i->j.seq;
+
+		*last_seq	= le64_to_cpu(i->j.last_seq);
+		*blacklist_seq	= le64_to_cpu(i->j.seq) + 1;
+		break;
+	}
+
+	if (!*start_seq) {
+		bch_info(c, "journal read done, but no entries found");
+		return 0;
+	}
+
+	if (!*last_seq) {
+		fsck_err(c, dirty_but_no_journal_entries_post_drop_nonflushes,
+			 "journal read done, but no entries found after dropping non-flushes");
+		return 0;
+	}
+
+	bch_info(c, "journal read done, replaying entries %llu-%llu",
+		 *last_seq, *blacklist_seq - 1);
+
+	if (*start_seq != *blacklist_seq)
+		bch_info(c, "dropped unflushed entries %llu-%llu",
+			 *blacklist_seq, *start_seq - 1);
+
+	/* Drop blacklisted entries and entries older than last_seq: */
+	genradix_for_each(&c->journal_entries, radix_iter, _i) {
+		i = *_i;
+
+		if (!i || i->ignore)
+			continue;
+
+		seq = le64_to_cpu(i->j.seq);
+		if (seq < *last_seq) {
+			journal_replay_free(c, i);
+			continue;
+		}
+
+		if (bch2_journal_seq_is_blacklisted(c, seq, true)) {
+			fsck_err_on(!JSET_NO_FLUSH(&i->j), c,
+				    jset_seq_blacklisted,
+				    "found blacklisted journal entry %llu", seq);
+			i->ignore = true;
+		}
+	}
+
+	/* Check for missing entries: */
+	seq = *last_seq;
+	genradix_for_each(&c->journal_entries, radix_iter, _i) {
+		i = *_i;
+
+		if (!i || i->ignore)
+			continue;
+
+		BUG_ON(seq > le64_to_cpu(i->j.seq));
+
+		while (seq < le64_to_cpu(i->j.seq)) {
+			u64 missing_start, missing_end;
+			struct printbuf buf1 = PRINTBUF, buf2 = PRINTBUF;
+
+			while (seq < le64_to_cpu(i->j.seq) &&
+			       bch2_journal_seq_is_blacklisted(c, seq, false))
+				seq++;
+
+			if (seq == le64_to_cpu(i->j.seq))
+				break;
+
+			missing_start = seq;
+
+			while (seq < le64_to_cpu(i->j.seq) &&
+			       !bch2_journal_seq_is_blacklisted(c, seq, false))
+				seq++;
+
+			if (prev) {
+				bch2_journal_ptrs_to_text(&buf1, c, prev);
+				prt_printf(&buf1, " size %zu", vstruct_sectors(&prev->j, c->block_bits));
+			} else
+				prt_printf(&buf1, "(none)");
+			bch2_journal_ptrs_to_text(&buf2, c, i);
+
+			missing_end = seq - 1;
+			fsck_err(c, journal_entries_missing,
+				 "journal entries %llu-%llu missing! (replaying %llu-%llu)\n"
+				 "  prev at %s\n"
+				 "  next at %s",
+				 missing_start, missing_end,
+				 *last_seq, *blacklist_seq - 1,
+				 buf1.buf, buf2.buf);
+
+			printbuf_exit(&buf1);
+			printbuf_exit(&buf2);
+		}
+
+		prev = i;
+		seq++;
+	}
+
+	genradix_for_each(&c->journal_entries, radix_iter, _i) {
+		struct bch_replicas_padded replicas = {
+			.e.data_type = BCH_DATA_journal,
+			.e.nr_required = 1,
+		};
+		unsigned ptr;
+
+		i = *_i;
+		if (!i || i->ignore)
+			continue;
+
+		for (ptr = 0; ptr < i->nr_ptrs; ptr++) {
+			ca = bch_dev_bkey_exists(c, i->ptrs[ptr].dev);
+
+			if (!i->ptrs[ptr].csum_good)
+				bch_err_dev_offset(ca, i->ptrs[ptr].sector,
+						   "invalid journal checksum, seq %llu%s",
+						   le64_to_cpu(i->j.seq),
+						   i->csum_good ? " (had good copy on another device)" : "");
+		}
+
+		ret = jset_validate(c,
+				    bch_dev_bkey_exists(c, i->ptrs[0].dev),
+				    &i->j,
+				    i->ptrs[0].sector,
+				    READ);
+		if (ret)
+			goto err;
+
+		for (ptr = 0; ptr < i->nr_ptrs; ptr++)
+			replicas.e.devs[replicas.e.nr_devs++] = i->ptrs[ptr].dev;
+
+		bch2_replicas_entry_sort(&replicas.e);
+
+		printbuf_reset(&buf);
+		bch2_replicas_entry_to_text(&buf, &replicas.e);
+
+		if (!degraded &&
+		    !bch2_replicas_marked(c, &replicas.e) &&
+		    (le64_to_cpu(i->j.seq) == *last_seq ||
+		     fsck_err(c, journal_entry_replicas_not_marked,
+			      "superblock not marked as containing replicas for journal entry %llu\n  %s",
+			      le64_to_cpu(i->j.seq), buf.buf))) {
+			ret = bch2_mark_replicas(c, &replicas.e);
+			if (ret)
+				goto err;
+		}
+	}
+err:
+fsck_err:
+	printbuf_exit(&buf);
+	return ret;
+}
+
+/* journal write: */
+
+static void __journal_write_alloc(struct journal *j,
+				  struct journal_buf *w,
+				  struct dev_alloc_list *devs_sorted,
+				  unsigned sectors,
+				  unsigned *replicas,
+				  unsigned replicas_want)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct journal_device *ja;
+	struct bch_dev *ca;
+	unsigned i;
+
+	if (*replicas >= replicas_want)
+		return;
+
+	for (i = 0; i < devs_sorted->nr; i++) {
+		ca = rcu_dereference(c->devs[devs_sorted->devs[i]]);
+		if (!ca)
+			continue;
+
+		ja = &ca->journal;
+
+		/*
+		 * Check that we can use this device, and aren't already using
+		 * it:
+		 */
+		if (!ca->mi.durability ||
+		    ca->mi.state != BCH_MEMBER_STATE_rw ||
+		    !ja->nr ||
+		    bch2_bkey_has_device_c(bkey_i_to_s_c(&w->key), ca->dev_idx) ||
+		    sectors > ja->sectors_free)
+			continue;
+
+		bch2_dev_stripe_increment(ca, &j->wp.stripe);
+
+		bch2_bkey_append_ptr(&w->key,
+			(struct bch_extent_ptr) {
+				  .offset = bucket_to_sector(ca,
+					ja->buckets[ja->cur_idx]) +
+					ca->mi.bucket_size -
+					ja->sectors_free,
+				  .dev = ca->dev_idx,
+		});
+
+		ja->sectors_free -= sectors;
+		ja->bucket_seq[ja->cur_idx] = le64_to_cpu(w->data->seq);
+
+		*replicas += ca->mi.durability;
+
+		if (*replicas >= replicas_want)
+			break;
+	}
+}
+
+/**
+ * journal_write_alloc - decide where to write next journal entry
+ *
+ * @j:		journal object
+ * @w:		journal buf (entry to be written)
+ *
+ * Returns: 0 on success, or -EROFS on failure
+ */
+static int journal_write_alloc(struct journal *j, struct journal_buf *w)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct bch_devs_mask devs;
+	struct journal_device *ja;
+	struct bch_dev *ca;
+	struct dev_alloc_list devs_sorted;
+	unsigned sectors = vstruct_sectors(w->data, c->block_bits);
+	unsigned target = c->opts.metadata_target ?:
+		c->opts.foreground_target;
+	unsigned i, replicas = 0, replicas_want =
+		READ_ONCE(c->opts.metadata_replicas);
+
+	rcu_read_lock();
+retry:
+	devs = target_rw_devs(c, BCH_DATA_journal, target);
+
+	devs_sorted = bch2_dev_alloc_list(c, &j->wp.stripe, &devs);
+
+	__journal_write_alloc(j, w, &devs_sorted,
+			      sectors, &replicas, replicas_want);
+
+	if (replicas >= replicas_want)
+		goto done;
+
+	for (i = 0; i < devs_sorted.nr; i++) {
+		ca = rcu_dereference(c->devs[devs_sorted.devs[i]]);
+		if (!ca)
+			continue;
+
+		ja = &ca->journal;
+
+		if (sectors > ja->sectors_free &&
+		    sectors <= ca->mi.bucket_size &&
+		    bch2_journal_dev_buckets_available(j, ja,
+					journal_space_discarded)) {
+			ja->cur_idx = (ja->cur_idx + 1) % ja->nr;
+			ja->sectors_free = ca->mi.bucket_size;
+
+			/*
+			 * ja->bucket_seq[ja->cur_idx] must always have
+			 * something sensible:
+			 */
+			ja->bucket_seq[ja->cur_idx] = le64_to_cpu(w->data->seq);
+		}
+	}
+
+	__journal_write_alloc(j, w, &devs_sorted,
+			      sectors, &replicas, replicas_want);
+
+	if (replicas < replicas_want && target) {
+		/* Retry from all devices: */
+		target = 0;
+		goto retry;
+	}
+done:
+	rcu_read_unlock();
+
+	BUG_ON(bkey_val_u64s(&w->key.k) > BCH_REPLICAS_MAX);
+
+	return replicas >= c->opts.metadata_replicas_required ? 0 : -EROFS;
+}
+
+static void journal_buf_realloc(struct journal *j, struct journal_buf *buf)
+{
+	/* we aren't holding j->lock: */
+	unsigned new_size = READ_ONCE(j->buf_size_want);
+	void *new_buf;
+
+	if (buf->buf_size >= new_size)
+		return;
+
+	new_buf = kvpmalloc(new_size, GFP_NOFS|__GFP_NOWARN);
+	if (!new_buf)
+		return;
+
+	memcpy(new_buf, buf->data, buf->buf_size);
+
+	spin_lock(&j->lock);
+	swap(buf->data,		new_buf);
+	swap(buf->buf_size,	new_size);
+	spin_unlock(&j->lock);
+
+	kvpfree(new_buf, new_size);
+}
+
+static inline struct journal_buf *journal_last_unwritten_buf(struct journal *j)
+{
+	return j->buf + (journal_last_unwritten_seq(j) & JOURNAL_BUF_MASK);
+}
+
+static CLOSURE_CALLBACK(journal_write_done)
+{
+	closure_type(j, struct journal, io);
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct journal_buf *w = journal_last_unwritten_buf(j);
+	struct bch_replicas_padded replicas;
+	union journal_res_state old, new;
+	u64 v, seq;
+	int err = 0;
+
+	bch2_time_stats_update(!JSET_NO_FLUSH(w->data)
+			       ? j->flush_write_time
+			       : j->noflush_write_time, j->write_start_time);
+
+	if (!w->devs_written.nr) {
+		bch_err(c, "unable to write journal to sufficient devices");
+		err = -EIO;
+	} else {
+		bch2_devlist_to_replicas(&replicas.e, BCH_DATA_journal,
+					 w->devs_written);
+		if (bch2_mark_replicas(c, &replicas.e))
+			err = -EIO;
+	}
+
+	if (err)
+		bch2_fatal_error(c);
+
+	spin_lock(&j->lock);
+	seq = le64_to_cpu(w->data->seq);
+
+	if (seq >= j->pin.front)
+		journal_seq_pin(j, seq)->devs = w->devs_written;
+
+	if (!err) {
+		if (!JSET_NO_FLUSH(w->data)) {
+			j->flushed_seq_ondisk = seq;
+			j->last_seq_ondisk = w->last_seq;
+
+			bch2_do_discards(c);
+			closure_wake_up(&c->freelist_wait);
+
+			bch2_reset_alloc_cursors(c);
+		}
+	} else if (!j->err_seq || seq < j->err_seq)
+		j->err_seq	= seq;
+
+	j->seq_ondisk		= seq;
+
+	/*
+	 * Updating last_seq_ondisk may let bch2_journal_reclaim_work() discard
+	 * more buckets:
+	 *
+	 * Must come before signaling write completion, for
+	 * bch2_fs_journal_stop():
+	 */
+	if (j->watermark != BCH_WATERMARK_stripe)
+		journal_reclaim_kick(&c->journal);
+
+	/* also must come before signalling write completion: */
+	closure_debug_destroy(cl);
+
+	v = atomic64_read(&j->reservations.counter);
+	do {
+		old.v = new.v = v;
+		BUG_ON(journal_state_count(new, new.unwritten_idx));
+
+		new.unwritten_idx++;
+	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
+				       old.v, new.v)) != old.v);
+
+	bch2_journal_reclaim_fast(j);
+	bch2_journal_space_available(j);
+
+	closure_wake_up(&w->wait);
+	journal_wake(j);
+
+	if (!journal_state_count(new, new.unwritten_idx) &&
+	    journal_last_unwritten_seq(j) <= journal_cur_seq(j)) {
+		spin_unlock(&j->lock);
+		closure_call(&j->io, bch2_journal_write, c->io_complete_wq, NULL);
+	} else if (journal_last_unwritten_seq(j) == journal_cur_seq(j) &&
+		   new.cur_entry_offset < JOURNAL_ENTRY_CLOSED_VAL) {
+		struct journal_buf *buf = journal_cur_buf(j);
+		long delta = buf->expires - jiffies;
+
+		/*
+		 * We don't close a journal entry to write it while there's
+		 * previous entries still in flight - the current journal entry
+		 * might want to be written now:
+		 */
+
+		spin_unlock(&j->lock);
+		mod_delayed_work(c->io_complete_wq, &j->write_work, max(0L, delta));
+	} else {
+		spin_unlock(&j->lock);
+	}
+}
+
+static void journal_write_endio(struct bio *bio)
+{
+	struct bch_dev *ca = bio->bi_private;
+	struct journal *j = &ca->fs->journal;
+	struct journal_buf *w = journal_last_unwritten_buf(j);
+	unsigned long flags;
+
+	if (bch2_dev_io_err_on(bio->bi_status, ca, BCH_MEMBER_ERROR_write,
+			       "error writing journal entry %llu: %s",
+			       le64_to_cpu(w->data->seq),
+			       bch2_blk_status_to_str(bio->bi_status)) ||
+	    bch2_meta_write_fault("journal")) {
+		spin_lock_irqsave(&j->err_lock, flags);
+		bch2_dev_list_drop_dev(&w->devs_written, ca->dev_idx);
+		spin_unlock_irqrestore(&j->err_lock, flags);
+	}
+
+	closure_put(&j->io);
+	percpu_ref_put(&ca->io_ref);
+}
+
+static CLOSURE_CALLBACK(do_journal_write)
+{
+	closure_type(j, struct journal, io);
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct bch_dev *ca;
+	struct journal_buf *w = journal_last_unwritten_buf(j);
+	struct bch_extent_ptr *ptr;
+	struct bio *bio;
+	unsigned sectors = vstruct_sectors(w->data, c->block_bits);
+
+	extent_for_each_ptr(bkey_i_to_s_extent(&w->key), ptr) {
+		ca = bch_dev_bkey_exists(c, ptr->dev);
+		if (!percpu_ref_tryget(&ca->io_ref)) {
+			/* XXX: fix this */
+			bch_err(c, "missing device for journal write\n");
+			continue;
+		}
+
+		this_cpu_add(ca->io_done->sectors[WRITE][BCH_DATA_journal],
+			     sectors);
+
+		bio = ca->journal.bio;
+		bio_reset(bio, ca->disk_sb.bdev, REQ_OP_WRITE|REQ_SYNC|REQ_META);
+		bio->bi_iter.bi_sector	= ptr->offset;
+		bio->bi_end_io		= journal_write_endio;
+		bio->bi_private		= ca;
+
+		BUG_ON(bio->bi_iter.bi_sector == ca->prev_journal_sector);
+		ca->prev_journal_sector = bio->bi_iter.bi_sector;
+
+		if (!JSET_NO_FLUSH(w->data))
+			bio->bi_opf    |= REQ_FUA;
+		if (!JSET_NO_FLUSH(w->data) && !w->separate_flush)
+			bio->bi_opf    |= REQ_PREFLUSH;
+
+		bch2_bio_map(bio, w->data, sectors << 9);
+
+		trace_and_count(c, journal_write, bio);
+		closure_bio_submit(bio, cl);
+
+		ca->journal.bucket_seq[ca->journal.cur_idx] =
+			le64_to_cpu(w->data->seq);
+	}
+
+	continue_at(cl, journal_write_done, c->io_complete_wq);
+}
+
+static int bch2_journal_write_prep(struct journal *j, struct journal_buf *w)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct jset_entry *start, *end, *i, *next, *prev = NULL;
+	struct jset *jset = w->data;
+	unsigned sectors, bytes, u64s;
+	bool validate_before_checksum = false;
+	unsigned long btree_roots_have = 0;
+	int ret;
+
+	/*
+	 * Simple compaction, dropping empty jset_entries (from journal
+	 * reservations that weren't fully used) and merging jset_entries that
+	 * can be.
+	 *
+	 * If we wanted to be really fancy here, we could sort all the keys in
+	 * the jset and drop keys that were overwritten - probably not worth it:
+	 */
+	vstruct_for_each_safe(jset, i, next) {
+		unsigned u64s = le16_to_cpu(i->u64s);
+
+		/* Empty entry: */
+		if (!u64s)
+			continue;
+
+		/*
+		 * New btree roots are set by journalling them; when the journal
+		 * entry gets written we have to propagate them to
+		 * c->btree_roots
+		 *
+		 * But, every journal entry we write has to contain all the
+		 * btree roots (at least for now); so after we copy btree roots
+		 * to c->btree_roots we have to get any missing btree roots and
+		 * add them to this journal entry:
+		 */
+		if (i->type == BCH_JSET_ENTRY_btree_root) {
+			bch2_journal_entry_to_btree_root(c, i);
+			__set_bit(i->btree_id, &btree_roots_have);
+		}
+
+		/* Can we merge with previous entry? */
+		if (prev &&
+		    i->btree_id == prev->btree_id &&
+		    i->level	== prev->level &&
+		    i->type	== prev->type &&
+		    i->type	== BCH_JSET_ENTRY_btree_keys &&
+		    le16_to_cpu(prev->u64s) + u64s <= U16_MAX) {
+			memmove_u64s_down(vstruct_next(prev),
+					  i->_data,
+					  u64s);
+			le16_add_cpu(&prev->u64s, u64s);
+			continue;
+		}
+
+		/* Couldn't merge, move i into new position (after prev): */
+		prev = prev ? vstruct_next(prev) : jset->start;
+		if (i != prev)
+			memmove_u64s_down(prev, i, jset_u64s(u64s));
+	}
+
+	prev = prev ? vstruct_next(prev) : jset->start;
+	jset->u64s = cpu_to_le32((u64 *) prev - jset->_data);
+
+	start = end = vstruct_last(jset);
+
+	end	= bch2_btree_roots_to_journal_entries(c, end, btree_roots_have);
+
+	bch2_journal_super_entries_add_common(c, &end,
+				le64_to_cpu(jset->seq));
+	u64s	= (u64 *) end - (u64 *) start;
+	BUG_ON(u64s > j->entry_u64s_reserved);
+
+	le32_add_cpu(&jset->u64s, u64s);
+
+	sectors = vstruct_sectors(jset, c->block_bits);
+	bytes	= vstruct_bytes(jset);
+
+	if (sectors > w->sectors) {
+		bch2_fs_fatal_error(c, "aieeee! journal write overran available space, %zu > %u (extra %u reserved %u/%u)",
+				    vstruct_bytes(jset), w->sectors << 9,
+				    u64s, w->u64s_reserved, j->entry_u64s_reserved);
+		return -EINVAL;
+	}
+
+	jset->magic		= cpu_to_le64(jset_magic(c));
+	jset->version		= cpu_to_le32(c->sb.version);
+
+	SET_JSET_BIG_ENDIAN(jset, CPU_BIG_ENDIAN);
+	SET_JSET_CSUM_TYPE(jset, bch2_meta_checksum_type(c));
+
+	if (!JSET_NO_FLUSH(jset) && journal_entry_empty(jset))
+		j->last_empty_seq = le64_to_cpu(jset->seq);
+
+	if (bch2_csum_type_is_encryption(JSET_CSUM_TYPE(jset)))
+		validate_before_checksum = true;
+
+	if (le32_to_cpu(jset->version) < bcachefs_metadata_version_current)
+		validate_before_checksum = true;
+
+	if (validate_before_checksum &&
+	    (ret = jset_validate(c, NULL, jset, 0, WRITE)))
+		return ret;
+
+	ret = bch2_encrypt(c, JSET_CSUM_TYPE(jset), journal_nonce(jset),
+		    jset->encrypted_start,
+		    vstruct_end(jset) - (void *) jset->encrypted_start);
+	if (bch2_fs_fatal_err_on(ret, c,
+			"error decrypting journal entry: %i", ret))
+		return ret;
+
+	jset->csum = csum_vstruct(c, JSET_CSUM_TYPE(jset),
+				  journal_nonce(jset), jset);
+
+	if (!validate_before_checksum &&
+	    (ret = jset_validate(c, NULL, jset, 0, WRITE)))
+		return ret;
+
+	memset((void *) jset + bytes, 0, (sectors << 9) - bytes);
+	return 0;
+}
+
+static int bch2_journal_write_pick_flush(struct journal *j, struct journal_buf *w)
+{
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	int error = bch2_journal_error(j);
+
+	/*
+	 * If the journal is in an error state - we did an emergency shutdown -
+	 * we prefer to continue doing journal writes. We just mark them as
+	 * noflush so they'll never be used, but they'll still be visible by the
+	 * list_journal tool - this helps in debugging.
+	 *
+	 * There's a caveat: the first journal write after marking the
+	 * superblock dirty must always be a flush write, because on startup
+	 * from a clean shutdown we didn't necessarily read the journal and the
+	 * new journal write might overwrite whatever was in the journal
+	 * previously - we can't leave the journal without any flush writes in
+	 * it.
+	 *
+	 * So if we're in an error state, and we're still starting up, we don't
+	 * write anything at all.
+	 */
+	if (error && test_bit(JOURNAL_NEED_FLUSH_WRITE, &j->flags))
+		return -EIO;
+
+	if (error ||
+	    w->noflush ||
+	    (!w->must_flush &&
+	     (jiffies - j->last_flush_write) < msecs_to_jiffies(c->opts.journal_flush_delay) &&
+	     test_bit(JOURNAL_MAY_SKIP_FLUSH, &j->flags))) {
+		     w->noflush = true;
+		SET_JSET_NO_FLUSH(w->data, true);
+		w->data->last_seq	= 0;
+		w->last_seq		= 0;
+
+		j->nr_noflush_writes++;
+	} else {
+		j->last_flush_write = jiffies;
+		j->nr_flush_writes++;
+		clear_bit(JOURNAL_NEED_FLUSH_WRITE, &j->flags);
+	}
+
+	return 0;
+}
+
+CLOSURE_CALLBACK(bch2_journal_write)
+{
+	closure_type(j, struct journal, io);
+	struct bch_fs *c = container_of(j, struct bch_fs, journal);
+	struct bch_dev *ca;
+	struct journal_buf *w = journal_last_unwritten_buf(j);
+	struct bch_replicas_padded replicas;
+	struct bio *bio;
+	struct printbuf journal_debug_buf = PRINTBUF;
+	unsigned i, nr_rw_members = 0;
+	int ret;
+
+	BUG_ON(BCH_SB_CLEAN(c->disk_sb.sb));
+
+	j->write_start_time = local_clock();
+
+	spin_lock(&j->lock);
+	ret = bch2_journal_write_pick_flush(j, w);
+	spin_unlock(&j->lock);
+	if (ret)
+		goto err;
+
+	journal_buf_realloc(j, w);
+
+	ret = bch2_journal_write_prep(j, w);
+	if (ret)
+		goto err;
+
+	while (1) {
+		spin_lock(&j->lock);
+		ret = journal_write_alloc(j, w);
+		if (!ret || !j->can_discard)
+			break;
+
+		spin_unlock(&j->lock);
+		bch2_journal_do_discards(j);
+	}
+
+	if (ret) {
+		__bch2_journal_debug_to_text(&journal_debug_buf, j);
+		spin_unlock(&j->lock);
+		bch_err(c, "Unable to allocate journal write:\n%s",
+			journal_debug_buf.buf);
+		printbuf_exit(&journal_debug_buf);
+		goto err;
+	}
+
+	/*
+	 * write is allocated, no longer need to account for it in
+	 * bch2_journal_space_available():
+	 */
+	w->sectors = 0;
+
+	/*
+	 * journal entry has been compacted and allocated, recalculate space
+	 * available:
+	 */
+	bch2_journal_space_available(j);
+	spin_unlock(&j->lock);
+
+	w->devs_written = bch2_bkey_devs(bkey_i_to_s_c(&w->key));
+
+	if (c->opts.nochanges)
+		goto no_io;
+
+	for_each_rw_member(ca, c, i)
+		nr_rw_members++;
+
+	if (nr_rw_members > 1)
+		w->separate_flush = true;
+
+	/*
+	 * Mark journal replicas before we submit the write to guarantee
+	 * recovery will find the journal entries after a crash.
+	 */
+	bch2_devlist_to_replicas(&replicas.e, BCH_DATA_journal,
+				 w->devs_written);
+	ret = bch2_mark_replicas(c, &replicas.e);
+	if (ret)
+		goto err;
+
+	if (!JSET_NO_FLUSH(w->data) && w->separate_flush) {
+		for_each_rw_member(ca, c, i) {
+			percpu_ref_get(&ca->io_ref);
+
+			bio = ca->journal.bio;
+			bio_reset(bio, ca->disk_sb.bdev,
+				  REQ_OP_WRITE|REQ_PREFLUSH);
+			bio->bi_end_io		= journal_write_endio;
+			bio->bi_private		= ca;
+			closure_bio_submit(bio, cl);
+		}
+	}
+
+	continue_at(cl, do_journal_write, c->io_complete_wq);
+	return;
+no_io:
+	continue_at(cl, journal_write_done, c->io_complete_wq);
+	return;
+err:
+	bch2_fatal_error(c);
+	continue_at(cl, journal_write_done, c->io_complete_wq);
+}