bcachefs: Start using bpos.snapshot field

This patch starts treating the bpos.snapshot field like part of the key
in the btree code:

* bpos_successor() and bpos_predecessor() now include the snapshot field
* Keys in btrees that will be using snapshots (extents, inodes, dirents
  and xattrs) now always have their snapshot field set to U32_MAX

The btree iterator code gets a new flag, BTREE_ITER_ALL_SNAPSHOTS, that
determines whether we're iterating over keys in all snapshots or not -
internally, this controlls whether bkey_(successor|predecessor)
increment/decrement the snapshot field, or only the higher bits of the
key.

We add a new member to struct btree_iter, iter->snapshot: when
BTREE_ITER_ALL_SNAPSHOTS is not set, iter->pos.snapshot should always
equal iter->snapshot, which will be 0 for btrees that don't use
snapshots, and alsways U32_MAX for btrees that will use snapshots
(until we enable snapshot creation).

This patch also introduces a new metadata version number, and compat
code for reading from/writing to older versions - this isn't a forced
upgrade (yet).

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

22 files changed, 251 insertions, 73 deletions

diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
index 111f7d3c312e..2172d3cf3680 100644
--- a/fs/bcachefs/bcachefs_format.h
+++ b/fs/bcachefs/bcachefs_format.h
@@ -142,19 +142,18 @@ struct bpos {
 #define KEY_SNAPSHOT_MAX		((__u32)~0U)
 #define KEY_SIZE_MAX			((__u32)~0U)
 
-static inline struct bpos POS(__u64 inode, __u64 offset)
+static inline struct bpos SPOS(__u64 inode, __u64 offset, __u32 snapshot)
 {
-	struct bpos ret;
-
-	ret.inode	= inode;
-	ret.offset	= offset;
-	ret.snapshot	= 0;
-
-	return ret;
+	return (struct bpos) {
+		.inode		= inode,
+		.offset		= offset,
+		.snapshot	= snapshot,
+	};
 }
 
-#define POS_MIN				POS(0, 0)
-#define POS_MAX				POS(KEY_INODE_MAX, KEY_OFFSET_MAX)
+#define POS_MIN				SPOS(0, 0, 0)
+#define POS_MAX				SPOS(KEY_INODE_MAX, KEY_OFFSET_MAX, KEY_SNAPSHOT_MAX)
+#define POS(_inode, _offset)		SPOS(_inode, _offset, 0)
 
 /* Empty placeholder struct, for container_of() */
 struct bch_val {
@@ -1208,7 +1207,8 @@ enum bcachefs_metadata_version {
 	bcachefs_metadata_version_new_versioning	= 10,
 	bcachefs_metadata_version_bkey_renumber		= 10,
 	bcachefs_metadata_version_inode_btree_change	= 11,
-	bcachefs_metadata_version_max			= 12,
+	bcachefs_metadata_version_snapshot		= 12,
+	bcachefs_metadata_version_max			= 13,
 };
 
 #define bcachefs_metadata_version_current	(bcachefs_metadata_version_max - 1)
@@ -1749,7 +1749,7 @@ struct btree_node {
 	/* Closed interval: */
 	struct bpos		min_key;
 	struct bpos		max_key;
-	struct bch_extent_ptr	ptr;
+	struct bch_extent_ptr	_ptr; /* not used anymore */
 	struct bkey_format	format;
 
 	union {
diff --git a/fs/bcachefs/bkey.c b/fs/bcachefs/bkey.c
index 8b2befac95d4..a0379f980f7e 100644
--- a/fs/bcachefs/bkey.c
+++ b/fs/bcachefs/bkey.c
@@ -617,15 +617,19 @@ const char *bch2_bkey_format_validate(struct bkey_format *f)
 		return "incorrect number of fields";
 
 	for (i = 0; i < f->nr_fields; i++) {
+		unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
+		u64 unpacked_mask = ~((~0ULL << 1) << (unpacked_bits - 1));
 		u64 field_offset = le64_to_cpu(f->field_offset[i]);
 
-		if (f->bits_per_field[i] > 64)
+		if (f->bits_per_field[i] > unpacked_bits)
 			return "field too large";
 
-		if (field_offset &&
-		    (f->bits_per_field[i] == 64 ||
-		    (field_offset + ((1ULL << f->bits_per_field[i]) - 1) <
-		     field_offset)))
+		if ((f->bits_per_field[i] == unpacked_bits) && field_offset)
+			return "offset + bits overflow";
+
+		if (((field_offset + ((1ULL << f->bits_per_field[i]) - 1)) &
+		     unpacked_mask) <
+		    field_offset)
 			return "offset + bits overflow";
 
 		bits += f->bits_per_field[i];
@@ -1126,11 +1130,12 @@ void bch2_bkey_pack_test(void)
 	struct bkey_packed p;
 
 	struct bkey_format test_format = {
-		.key_u64s	= 2,
+		.key_u64s	= 3,
 		.nr_fields	= BKEY_NR_FIELDS,
 		.bits_per_field = {
 			13,
 			64,
+			32,
 		},
 	};
 
diff --git a/fs/bcachefs/bkey.h b/fs/bcachefs/bkey.h
index df23c5b48969..72b4267031d8 100644
--- a/fs/bcachefs/bkey.h
+++ b/fs/bcachefs/bkey.h
@@ -258,24 +258,46 @@ static inline unsigned bkey_format_key_bits(const struct bkey_format *format)
 		format->bits_per_field[BKEY_FIELD_SNAPSHOT];
 }
 
-static inline struct bpos bkey_successor(struct bpos p)
+static inline struct bpos bpos_successor(struct bpos p)
 {
-	struct bpos ret = p;
+	if (!++p.snapshot &&
+	    !++p.offset &&
+	    !++p.inode)
+		BUG();
 
-	if (!++ret.offset)
-		BUG_ON(!++ret.inode);
+	return p;
+}
 
-	return ret;
+static inline struct bpos bpos_predecessor(struct bpos p)
+{
+	if (!p.snapshot-- &&
+	    !p.offset-- &&
+	    !p.inode--)
+		BUG();
+
+	return p;
 }
 
-static inline struct bpos bkey_predecessor(struct bpos p)
+static inline struct bpos bpos_nosnap_successor(struct bpos p)
 {
-	struct bpos ret = p;
+	p.snapshot = 0;
 
-	if (!ret.offset--)
-		BUG_ON(!ret.inode--);
+	if (!++p.offset &&
+	    !++p.inode)
+		BUG();
 
-	return ret;
+	return p;
+}
+
+static inline struct bpos bpos_nosnap_predecessor(struct bpos p)
+{
+	p.snapshot = 0;
+
+	if (!p.offset-- &&
+	    !p.inode--)
+		BUG();
+
+	return p;
 }
 
 static inline u64 bkey_start_offset(const struct bkey *k)
diff --git a/fs/bcachefs/bkey_methods.c b/fs/bcachefs/bkey_methods.c
index 5e7eadeb3b57..6fe95b802e13 100644
--- a/fs/bcachefs/bkey_methods.c
+++ b/fs/bcachefs/bkey_methods.c
@@ -119,10 +119,17 @@ const char *__bch2_bkey_invalid(struct bch_fs *c, struct bkey_s_c k,
 			return "nonzero size field";
 	}
 
-	if (k.k->p.snapshot)
+	if (type != BKEY_TYPE_btree &&
+	    !btree_type_has_snapshots(type) &&
+	    k.k->p.snapshot)
 		return "nonzero snapshot";
 
 	if (type != BKEY_TYPE_btree &&
+	    btree_type_has_snapshots(type) &&
+	    k.k->p.snapshot != U32_MAX)
+		return "invalid snapshot field";
+
+	if (type != BKEY_TYPE_btree &&
 	    !bkey_cmp(k.k->p, POS_MAX))
 		return "POS_MAX key";
 
@@ -310,14 +317,15 @@ void __bch2_bkey_compat(unsigned level, enum btree_id btree_id,
 	const struct bkey_ops *ops;
 	struct bkey uk;
 	struct bkey_s u;
+	unsigned nr_compat = 5;
 	int i;
 
 	/*
 	 * Do these operations in reverse order in the write path:
 	 */
 
-	for (i = 0; i < 4; i++)
-	switch (!write ? i : 3 - i) {
+	for (i = 0; i < nr_compat; i++)
+	switch (!write ? i : nr_compat - 1 - i) {
 	case 0:
 		if (big_endian != CPU_BIG_ENDIAN)
 			bch2_bkey_swab_key(f, k);
@@ -351,6 +359,28 @@ void __bch2_bkey_compat(unsigned level, enum btree_id btree_id,
 		}
 		break;
 	case 3:
+		if (version < bcachefs_metadata_version_snapshot &&
+		    (level || btree_type_has_snapshots(btree_id))) {
+			struct bkey_i *u = packed_to_bkey(k);
+
+			if (u) {
+				u->k.p.snapshot = write
+					? 0 : U32_MAX;
+			} else {
+				u64 min_packed = f->field_offset[BKEY_FIELD_SNAPSHOT];
+				u64 max_packed = min_packed +
+					~(~0ULL << f->bits_per_field[BKEY_FIELD_SNAPSHOT]);
+
+				uk = __bch2_bkey_unpack_key(f, k);
+				uk.p.snapshot = write
+					? min_packed : min_t(u64, U32_MAX, max_packed);
+
+				BUG_ON(!bch2_bkey_pack_key(k, &uk, f));
+			}
+		}
+
+		break;
+	case 4:
 		if (!bkey_packed(k)) {
 			u = bkey_i_to_s(packed_to_bkey(k));
 		} else {
diff --git a/fs/bcachefs/bset.c b/fs/bcachefs/bset.c
index 5746199dfafb..de4dc2fac1d6 100644
--- a/fs/bcachefs/bset.c
+++ b/fs/bcachefs/bset.c
@@ -1438,7 +1438,7 @@ static void btree_node_iter_init_pack_failed(struct btree_node_iter *iter,
  *    to the search key is going to have 0 sectors after the search key.
  *
  *    But this does mean that we can't just search for
- *    bkey_successor(start_of_range) to get the first extent that overlaps with
+ *    bpos_successor(start_of_range) to get the first extent that overlaps with
  *    the range we want - if we're unlucky and there's an extent that ends
  *    exactly where we searched, then there could be a deleted key at the same
  *    position and we'd get that when we search instead of the preceding extent
diff --git a/fs/bcachefs/btree_cache.c b/fs/bcachefs/btree_cache.c
index 63b8423fa87c..85ac08b9270a 100644
--- a/fs/bcachefs/btree_cache.c
+++ b/fs/bcachefs/btree_cache.c
@@ -1018,7 +1018,7 @@ out:
 		if (sib != btree_prev_sib)
 			swap(n1, n2);
 
-		if (bpos_cmp(bkey_successor(n1->key.k.p),
+		if (bpos_cmp(bpos_successor(n1->key.k.p),
 			     n2->data->min_key)) {
 			char buf1[200], buf2[200];
 
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 2710e4b35da3..842840664562 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -64,7 +64,7 @@ static int bch2_gc_check_topology(struct bch_fs *c,
 	struct bpos node_end	= b->data->max_key;
 	struct bpos expected_start = bkey_deleted(&prev->k->k)
 		? node_start
-		: bkey_successor(prev->k->k.p);
+		: bpos_successor(prev->k->k.p);
 	char buf1[200], buf2[200];
 	bool update_min = false;
 	bool update_max = false;
@@ -1187,7 +1187,9 @@ static int bch2_gc_btree_gens(struct bch_fs *c, enum btree_id btree_id)
 	bch2_trans_init(&trans, c, 0, 0);
 
 	iter = bch2_trans_get_iter(&trans, btree_id, POS_MIN,
-				   BTREE_ITER_PREFETCH);
+				   BTREE_ITER_PREFETCH|
+				   BTREE_ITER_NOT_EXTENTS|
+				   BTREE_ITER_ALL_SNAPSHOTS);
 
 	while ((k = bch2_btree_iter_peek(iter)).k &&
 	       !(ret = bkey_err(k))) {
@@ -1405,7 +1407,7 @@ static void bch2_coalesce_nodes(struct bch_fs *c, struct btree_iter *iter,
 			n1->key.k.p = n1->data->max_key =
 				bkey_unpack_pos(n1, last);
 
-			n2->data->min_key = bkey_successor(n1->data->max_key);
+			n2->data->min_key = bpos_successor(n1->data->max_key);
 
 			memcpy_u64s(vstruct_last(s1),
 				    s2->start, u64s);
diff --git a/fs/bcachefs/btree_io.c b/fs/bcachefs/btree_io.c
index 468b1a294ce9..bc09f9377425 100644
--- a/fs/bcachefs/btree_io.c
+++ b/fs/bcachefs/btree_io.c
@@ -612,12 +612,6 @@ static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
 			     BTREE_ERR_MUST_RETRY, c, ca, b, i,
 			     "incorrect level");
 
-		if (BSET_BIG_ENDIAN(i) != CPU_BIG_ENDIAN) {
-			u64 *p = (u64 *) &bn->ptr;
-
-			*p = swab64(*p);
-		}
-
 		if (!write)
 			compat_btree_node(b->c.level, b->c.btree_id, version,
 					  BSET_BIG_ENDIAN(i), write, bn);
@@ -1328,8 +1322,8 @@ static int validate_bset_for_write(struct bch_fs *c, struct btree *b,
 	if (bch2_bkey_invalid(c, bkey_i_to_s_c(&b->key), BKEY_TYPE_btree))
 		return -1;
 
-	ret = validate_bset(c, NULL, b, i, sectors, WRITE, false) ?:
-		validate_bset_keys(c, b, i, &whiteout_u64s, WRITE, false);
+	ret = validate_bset_keys(c, b, i, &whiteout_u64s, WRITE, false) ?:
+		validate_bset(c, NULL, b, i, sectors, WRITE, false);
 	if (ret) {
 		bch2_inconsistent_error(c);
 		dump_stack();
@@ -1482,7 +1476,7 @@ void __bch2_btree_node_write(struct bch_fs *c, struct btree *b,
 		validate_before_checksum = true;
 
 	/* validate_bset will be modifying: */
-	if (le16_to_cpu(i->version) <= bcachefs_metadata_version_inode_btree_change)
+	if (le16_to_cpu(i->version) < bcachefs_metadata_version_current)
 		validate_before_checksum = true;
 
 	/* if we're going to be encrypting, check metadata validity first: */
diff --git a/fs/bcachefs/btree_io.h b/fs/bcachefs/btree_io.h
index f155a6cc1755..9c14cd30a09e 100644
--- a/fs/bcachefs/btree_io.h
+++ b/fs/bcachefs/btree_io.h
@@ -189,8 +189,8 @@ void bch2_btree_flush_all_writes(struct bch_fs *);
 void bch2_dirty_btree_nodes_to_text(struct printbuf *, struct bch_fs *);
 
 static inline void compat_bformat(unsigned level, enum btree_id btree_id,
-				 unsigned version, unsigned big_endian,
-				 int write, struct bkey_format *f)
+				  unsigned version, unsigned big_endian,
+				  int write, struct bkey_format *f)
 {
 	if (version < bcachefs_metadata_version_inode_btree_change &&
 	    btree_id == BTREE_ID_inodes) {
@@ -199,6 +199,16 @@ static inline void compat_bformat(unsigned level, enum btree_id btree_id,
 		swap(f->field_offset[BKEY_FIELD_INODE],
 		     f->field_offset[BKEY_FIELD_OFFSET]);
 	}
+
+	if (version < bcachefs_metadata_version_snapshot &&
+	    (level || btree_type_has_snapshots(btree_id))) {
+		u64 max_packed =
+			~(~0ULL << f->bits_per_field[BKEY_FIELD_SNAPSHOT]);
+
+		f->field_offset[BKEY_FIELD_SNAPSHOT] = write
+			? 0
+			: U32_MAX - max_packed;
+	}
 }
 
 static inline void compat_bpos(unsigned level, enum btree_id btree_id,
@@ -222,16 +232,24 @@ static inline void compat_btree_node(unsigned level, enum btree_id btree_id,
 	    btree_node_type_is_extents(btree_id) &&
 	    bpos_cmp(bn->min_key, POS_MIN) &&
 	    write)
-		bn->min_key = bkey_predecessor(bn->min_key);
+		bn->min_key = bpos_nosnap_predecessor(bn->min_key);
+
+	if (version < bcachefs_metadata_version_snapshot &&
+	    write)
+		bn->max_key.snapshot = 0;
 
 	compat_bpos(level, btree_id, version, big_endian, write, &bn->min_key);
 	compat_bpos(level, btree_id, version, big_endian, write, &bn->max_key);
 
+	if (version < bcachefs_metadata_version_snapshot &&
+	    !write)
+		bn->max_key.snapshot = U32_MAX;
+
 	if (version < bcachefs_metadata_version_inode_btree_change &&
 	    btree_node_type_is_extents(btree_id) &&
 	    bpos_cmp(bn->min_key, POS_MIN) &&
 	    !write)
-		bn->min_key = bkey_successor(bn->min_key);
+		bn->min_key = bpos_nosnap_successor(bn->min_key);
 }
 
 #endif /* _BCACHEFS_BTREE_IO_H */
diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 8c923aa01ea1..972486a1f724 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -18,6 +18,36 @@
 
 static void btree_iter_set_search_pos(struct btree_iter *, struct bpos);
 
+static inline struct bpos bkey_successor(struct btree_iter *iter, struct bpos p)
+{
+	EBUG_ON(btree_iter_type(iter) == BTREE_ITER_NODES);
+
+	/* Are we iterating over keys in all snapshots? */
+	if (iter->flags & BTREE_ITER_ALL_SNAPSHOTS) {
+		p = bpos_successor(p);
+	} else {
+		p = bpos_nosnap_successor(p);
+		p.snapshot = iter->snapshot;
+	}
+
+	return p;
+}
+
+static inline struct bpos bkey_predecessor(struct btree_iter *iter, struct bpos p)
+{
+	EBUG_ON(btree_iter_type(iter) == BTREE_ITER_NODES);
+
+	/* Are we iterating over keys in all snapshots? */
+	if (iter->flags & BTREE_ITER_ALL_SNAPSHOTS) {
+		p = bpos_predecessor(p);
+	} else {
+		p = bpos_nosnap_predecessor(p);
+		p.snapshot = iter->snapshot;
+	}
+
+	return p;
+}
+
 static inline bool is_btree_node(struct btree_iter *iter, unsigned l)
 {
 	return l < BTREE_MAX_DEPTH &&
@@ -30,7 +60,7 @@ static inline struct bpos btree_iter_search_key(struct btree_iter *iter)
 
 	if ((iter->flags & BTREE_ITER_IS_EXTENTS) &&
 	    bkey_cmp(pos, POS_MAX))
-		pos = bkey_successor(pos);
+		pos = bkey_successor(iter, pos);
 	return pos;
 }
 
@@ -591,10 +621,24 @@ err:
 
 static void bch2_btree_iter_verify(struct btree_iter *iter)
 {
+	enum btree_iter_type type = btree_iter_type(iter);
 	unsigned i;
 
 	EBUG_ON(iter->btree_id >= BTREE_ID_NR);
 
+	BUG_ON(!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
+	       iter->pos.snapshot != iter->snapshot);
+
+	BUG_ON((iter->flags & BTREE_ITER_IS_EXTENTS) &&
+	       (iter->flags & BTREE_ITER_ALL_SNAPSHOTS));
+
+	BUG_ON(type == BTREE_ITER_NODES &&
+	       !(iter->flags & BTREE_ITER_ALL_SNAPSHOTS));
+
+	BUG_ON(type != BTREE_ITER_NODES &&
+	       (iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
+	       !btree_type_has_snapshots(iter->btree_id));
+
 	bch2_btree_iter_verify_locks(iter);
 
 	for (i = 0; i < BTREE_MAX_DEPTH; i++)
@@ -605,6 +649,9 @@ static void bch2_btree_iter_verify_entry_exit(struct btree_iter *iter)
 {
 	enum btree_iter_type type = btree_iter_type(iter);
 
+	BUG_ON(!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS) &&
+	       iter->pos.snapshot != iter->snapshot);
+
 	BUG_ON((type == BTREE_ITER_KEYS ||
 		type == BTREE_ITER_CACHED) &&
 	       (bkey_cmp(iter->pos, bkey_start_pos(&iter->k)) < 0 ||
@@ -1434,7 +1481,7 @@ struct btree *bch2_btree_iter_next_node(struct btree_iter *iter)
 		 * Haven't gotten to the end of the parent node: go back down to
 		 * the next child node
 		 */
-		btree_iter_set_search_pos(iter, bkey_successor(iter->pos));
+		btree_iter_set_search_pos(iter, bpos_successor(iter->pos));
 
 		/* Unlock to avoid screwing up our lock invariants: */
 		btree_node_unlock(iter, iter->level);
@@ -1508,7 +1555,7 @@ inline bool bch2_btree_iter_advance(struct btree_iter *iter)
 	bool ret = bpos_cmp(pos, POS_MAX) != 0;
 
 	if (ret && !(iter->flags & BTREE_ITER_IS_EXTENTS))
-		pos = bkey_successor(pos);
+		pos = bkey_successor(iter, pos);
 	bch2_btree_iter_set_pos(iter, pos);
 	return ret;
 }
@@ -1519,7 +1566,7 @@ inline bool bch2_btree_iter_rewind(struct btree_iter *iter)
 	bool ret = bpos_cmp(pos, POS_MIN) != 0;
 
 	if (ret && !(iter->flags & BTREE_ITER_IS_EXTENTS))
-		pos = bkey_predecessor(pos);
+		pos = bkey_predecessor(iter, pos);
 	bch2_btree_iter_set_pos(iter, pos);
 	return ret;
 }
@@ -1535,7 +1582,7 @@ static inline bool btree_iter_set_pos_to_next_leaf(struct btree_iter *iter)
 	 * btree, in that case we want iter->pos to reflect that:
 	 */
 	if (ret)
-		btree_iter_set_search_pos(iter, bkey_successor(next_pos));
+		btree_iter_set_search_pos(iter, bpos_successor(next_pos));
 	else
 		bch2_btree_iter_set_pos(iter, POS_MAX);
 
@@ -1548,7 +1595,7 @@ static inline bool btree_iter_set_pos_to_prev_leaf(struct btree_iter *iter)
 	bool ret = bpos_cmp(next_pos, POS_MIN) != 0;
 
 	if (ret)
-		btree_iter_set_search_pos(iter, bkey_predecessor(next_pos));
+		btree_iter_set_search_pos(iter, bpos_predecessor(next_pos));
 	else
 		bch2_btree_iter_set_pos(iter, POS_MIN);
 
@@ -1594,13 +1641,13 @@ static inline struct bkey_s_c __btree_iter_peek(struct btree_iter *iter, bool wi
 		k = btree_iter_level_peek(iter, &iter->l[0]);
 
 		if (next_update &&
-		    bkey_cmp(next_update->k.p, iter->real_pos) <= 0)
+		    bpos_cmp(next_update->k.p, iter->real_pos) <= 0)
 			k = bkey_i_to_s_c(next_update);
 
 		if (likely(k.k)) {
 			if (bkey_deleted(k.k)) {
 				btree_iter_set_search_pos(iter,
-						bkey_successor(k.k->p));
+						bkey_successor(iter, k.k->p));
 				continue;
 			}
 
@@ -1739,7 +1786,7 @@ __bch2_btree_iter_peek_slot_extents(struct btree_iter *iter)
 		if (iter->pos.inode == KEY_INODE_MAX)
 			return bkey_s_c_null;
 
-		bch2_btree_iter_set_pos(iter, bkey_successor(iter->pos));
+		bch2_btree_iter_set_pos(iter, bkey_successor(iter, iter->pos));
 	}
 
 	pos = iter->pos;
@@ -1973,6 +2020,14 @@ struct btree_iter *__bch2_trans_get_iter(struct btree_trans *trans,
 {
 	struct btree_iter *iter, *best = NULL;
 
+	if ((flags & BTREE_ITER_TYPE) != BTREE_ITER_NODES &&
+	    !btree_type_has_snapshots(btree_id))
+		flags &= ~BTREE_ITER_ALL_SNAPSHOTS;
+
+	if (!(flags & BTREE_ITER_ALL_SNAPSHOTS))
+		pos.snapshot = btree_type_has_snapshots(btree_id)
+			? U32_MAX : 0;
+
 	/* We always want a fresh iterator for node iterators: */
 	if ((flags & BTREE_ITER_TYPE) == BTREE_ITER_NODES)
 		goto alloc_iter;
@@ -2007,11 +2062,14 @@ alloc_iter:
 
 	if ((flags & BTREE_ITER_TYPE) != BTREE_ITER_NODES &&
 	    btree_node_type_is_extents(btree_id) &&
-	    !(flags & BTREE_ITER_NOT_EXTENTS))
+	    !(flags & BTREE_ITER_NOT_EXTENTS) &&
+	    !(flags & BTREE_ITER_ALL_SNAPSHOTS))
 		flags |= BTREE_ITER_IS_EXTENTS;
 
 	iter->flags = flags;
 
+	iter->snapshot = pos.snapshot;
+
 	if (!(iter->flags & BTREE_ITER_INTENT))
 		bch2_btree_iter_downgrade(iter);
 	else if (!iter->locks_want)
@@ -2034,6 +2092,7 @@ struct btree_iter *bch2_trans_get_node_iter(struct btree_trans *trans,
 		__bch2_trans_get_iter(trans, btree_id, pos,
 				       BTREE_ITER_NODES|
 				       BTREE_ITER_NOT_EXTENTS|
+				       BTREE_ITER_ALL_SNAPSHOTS|
 				       flags);
 	unsigned i;
 
diff --git a/fs/bcachefs/btree_iter.h b/fs/bcachefs/btree_iter.h
index 176661b3b879..7585f989ad50 100644
--- a/fs/bcachefs/btree_iter.h
+++ b/fs/bcachefs/btree_iter.h
@@ -172,6 +172,9 @@ bool bch2_btree_iter_rewind(struct btree_iter *);
 
 static inline void bch2_btree_iter_set_pos(struct btree_iter *iter, struct bpos new_pos)
 {
+	if (!(iter->flags & BTREE_ITER_ALL_SNAPSHOTS))
+		new_pos.snapshot = iter->snapshot;
+
 	bkey_init(&iter->k);
 	iter->k.p = iter->pos = new_pos;
 }
diff --git a/fs/bcachefs/btree_types.h b/fs/bcachefs/btree_types.h
index bcd8db34d7ee..0bcf17159744 100644
--- a/fs/bcachefs/btree_types.h
+++ b/fs/bcachefs/btree_types.h
@@ -216,6 +216,7 @@ enum btree_iter_type {
 #define BTREE_ITER_CACHED_NOFILL	(1 << 9)
 #define BTREE_ITER_CACHED_NOCREATE	(1 << 10)
 #define BTREE_ITER_NOT_EXTENTS		(1 << 11)
+#define BTREE_ITER_ALL_SNAPSHOTS	(1 << 12)
 
 enum btree_iter_uptodate {
 	BTREE_ITER_UPTODATE		= 0,
@@ -245,6 +246,8 @@ struct btree_iter {
 	/* what we're searching for/what the iterator actually points to: */
 	struct bpos		real_pos;
 	struct bpos		pos_after_commit;
+	/* When we're filtering by snapshot, the snapshot ID we're looking for: */
+	unsigned		snapshot;
 
 	u16			flags;
 	u8			idx;
@@ -329,7 +332,7 @@ struct bkey_cached {
 struct btree_insert_entry {
 	unsigned		trigger_flags;
 	u8			bkey_type;
-	u8			btree_id;
+	enum btree_id		btree_id:8;
 	u8			level;
 	unsigned		trans_triggers_run:1;
 	unsigned		is_extent:1;
@@ -610,6 +613,17 @@ static inline bool btree_iter_is_extents(struct btree_iter *iter)
 	(BTREE_NODE_TYPE_HAS_TRANS_TRIGGERS|		\
 	 BTREE_NODE_TYPE_HAS_MEM_TRIGGERS)
 
+#define BTREE_ID_HAS_SNAPSHOTS				\
+	((1U << BTREE_ID_extents)|			\
+	 (1U << BTREE_ID_inodes)|			\
+	 (1U << BTREE_ID_dirents)|			\
+	 (1U << BTREE_ID_xattrs))
+
+static inline bool btree_type_has_snapshots(enum btree_id id)
+{
+	return (1 << id) & BTREE_ID_HAS_SNAPSHOTS;
+}
+
 enum btree_trigger_flags {
 	__BTREE_TRIGGER_NORUN,		/* Don't run triggers at all */
 
diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index ddb0d03e268c..aad262937645 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -69,7 +69,7 @@ static void btree_node_interior_verify(struct bch_fs *c, struct btree *b)
 			break;
 		}
 
-		next_node = bkey_successor(k.k->p);
+		next_node = bpos_successor(k.k->p);
 	}
 #endif
 }
@@ -289,7 +289,6 @@ static struct btree *bch2_btree_node_alloc(struct btree_update *as, unsigned lev
 	b->data->flags = 0;
 	SET_BTREE_NODE_ID(b->data, as->btree_id);
 	SET_BTREE_NODE_LEVEL(b->data, level);
-	b->data->ptr = bch2_bkey_ptrs_c(bkey_i_to_s_c(&b->key)).start->ptr;
 
 	if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
 		struct bkey_i_btree_ptr_v2 *bp = bkey_i_to_btree_ptr_v2(&b->key);
@@ -1100,6 +1099,7 @@ static struct btree *__btree_split_node(struct btree_update *as,
 	struct btree *n2;
 	struct bset *set1, *set2;
 	struct bkey_packed *k, *set2_start, *set2_end, *out, *prev = NULL;
+	struct bpos n1_pos;
 
 	n2 = bch2_btree_node_alloc(as, n1->c.level);
 	bch2_btree_update_add_new_node(as, n2);
@@ -1146,8 +1146,12 @@ static struct btree *__btree_split_node(struct btree_update *as,
 	n1->nr.packed_keys	= nr_packed;
 	n1->nr.unpacked_keys	= nr_unpacked;
 
-	btree_set_max(n1, bkey_unpack_pos(n1, prev));
-	btree_set_min(n2, bkey_successor(n1->key.k.p));
+	n1_pos = bkey_unpack_pos(n1, prev);
+	if (as->c->sb.version < bcachefs_metadata_version_snapshot)
+		n1_pos.snapshot = U32_MAX;
+
+	btree_set_max(n1, n1_pos);
+	btree_set_min(n2, bpos_successor(n1->key.k.p));
 
 	bch2_bkey_format_init(&s);
 	bch2_bkey_format_add_pos(&s, n2->data->min_key);
diff --git a/fs/bcachefs/btree_update_leaf.c b/fs/bcachefs/btree_update_leaf.c
index a32c8f34039c..88da89e8b170 100644
--- a/fs/bcachefs/btree_update_leaf.c
+++ b/fs/bcachefs/btree_update_leaf.c
@@ -223,9 +223,17 @@ static inline void btree_insert_entry_checks(struct btree_trans *trans,
 {
 	struct bch_fs *c = trans->c;
 
-	BUG_ON(bch2_debug_check_bkeys &&
-	       bch2_bkey_invalid(c, bkey_i_to_s_c(i->k), i->bkey_type));
-	BUG_ON(bpos_cmp(i->k->k.p, i->iter->real_pos));
+	if (bch2_debug_check_bkeys) {
+		const char *invalid = bch2_bkey_invalid(c,
+				bkey_i_to_s_c(i->k), i->bkey_type);
+		if (invalid) {
+			char buf[200];
+
+			bch2_bkey_val_to_text(&PBUF(buf), c, bkey_i_to_s_c(i->k));
+			panic("invalid bkey %s on insert: %s\n", buf, invalid);
+		}
+	}
+	BUG_ON(!i->is_extent && bpos_cmp(i->k->k.p, i->iter->real_pos));
 	BUG_ON(i->level		!= i->iter->level);
 	BUG_ON(i->btree_id	!= i->iter->btree_id);
 }
diff --git a/fs/bcachefs/debug.c b/fs/bcachefs/debug.c
index 059972e5a124..111310344cec 100644
--- a/fs/bcachefs/debug.c
+++ b/fs/bcachefs/debug.c
@@ -222,7 +222,9 @@ static ssize_t bch2_read_btree(struct file *file, char __user *buf,
 
 	bch2_trans_init(&trans, i->c, 0, 0);
 
-	iter = bch2_trans_get_iter(&trans, i->id, i->from, BTREE_ITER_PREFETCH);
+	iter = bch2_trans_get_iter(&trans, i->id, i->from,
+				   BTREE_ITER_PREFETCH|
+				   BTREE_ITER_ALL_SNAPSHOTS);
 	k = bch2_btree_iter_peek(iter);
 
 	while (k.k && !(err = bkey_err(k))) {
@@ -290,7 +292,7 @@ static ssize_t bch2_read_btree_formats(struct file *file, char __user *buf,
 		 * all nodes, meh
 		 */
 		i->from = bpos_cmp(POS_MAX, b->key.k.p)
-			? bkey_successor(b->key.k.p)
+			? bpos_successor(b->key.k.p)
 			: b->key.k.p;
 
 		if (!i->size)
diff --git a/fs/bcachefs/extents.c b/fs/bcachefs/extents.c
index 7ac3d7587655..1f28dea26ca2 100644
--- a/fs/bcachefs/extents.c
+++ b/fs/bcachefs/extents.c
@@ -179,7 +179,8 @@ const char *bch2_btree_ptr_v2_invalid(const struct bch_fs *c, struct bkey_s_c k)
 	if (bkey_val_u64s(k.k) > BKEY_BTREE_PTR_VAL_U64s_MAX)
 		return "value too big";
 
-	if (bp.v->min_key.snapshot)
+	if (c->sb.version < bcachefs_metadata_version_snapshot &&
+	    bp.v->min_key.snapshot)
 		return "invalid min_key.snapshot";
 
 	return bch2_bkey_ptrs_invalid(c, k);
@@ -211,8 +212,8 @@ void bch2_btree_ptr_v2_compat(enum btree_id btree_id, unsigned version,
 	    btree_node_type_is_extents(btree_id) &&
 	    bkey_cmp(bp.v->min_key, POS_MIN))
 		bp.v->min_key = write
-			? bkey_predecessor(bp.v->min_key)
-			: bkey_successor(bp.v->min_key);
+			? bpos_nosnap_predecessor(bp.v->min_key)
+			: bpos_nosnap_successor(bp.v->min_key);
 }
 
 /* KEY_TYPE_extent: */
diff --git a/fs/bcachefs/fsck.c b/fs/bcachefs/fsck.c
index ffb30ef7ef00..a3acae0ddfa9 100644
--- a/fs/bcachefs/fsck.c
+++ b/fs/bcachefs/fsck.c
@@ -1318,6 +1318,7 @@ static int check_inode(struct btree_trans *trans,
 		struct bkey_inode_buf p;
 
 		bch2_inode_pack(c, &p, &u);
+		p.inode.k.p = iter->pos;
 
 		ret = __bch2_trans_do(trans, NULL, NULL,
 				      BTREE_INSERT_NOFAIL|
diff --git a/fs/bcachefs/inode.c b/fs/bcachefs/inode.c
index f676daf404a2..7044ab73831c 100644
--- a/fs/bcachefs/inode.c
+++ b/fs/bcachefs/inode.c
@@ -332,6 +332,7 @@ int bch2_inode_write(struct btree_trans *trans,
 		return PTR_ERR(inode_p);
 
 	bch2_inode_pack(trans->c, inode_p, inode);
+	inode_p->inode.k.p.snapshot = iter->snapshot;
 	bch2_trans_update(trans, iter, &inode_p->inode.k_i, 0);
 	return 0;
 }
diff --git a/fs/bcachefs/io.c b/fs/bcachefs/io.c
index 5ee9a6c2f4fd..9c46f67c0d8e 100644
--- a/fs/bcachefs/io.c
+++ b/fs/bcachefs/io.c
@@ -332,6 +332,9 @@ int bch2_extent_update(struct btree_trans *trans,
 
 		if (i_sectors_delta || new_i_size) {
 			bch2_inode_pack(trans->c, &inode_p, &inode_u);
+
+			inode_p.inode.k.p.snapshot = iter->snapshot;
+
 			bch2_trans_update(trans, inode_iter,
 					  &inode_p.inode.k_i, 0);
 		}
@@ -447,6 +450,8 @@ int bch2_write_index_default(struct bch_write_op *op)
 
 		k = bch2_keylist_front(keys);
 
+		k->k.p.snapshot = iter->snapshot;
+
 		bch2_bkey_buf_realloc(&sk, c, k->k.u64s);
 		bkey_copy(sk.k, k);
 		bch2_cut_front(iter->pos, sk.k);
diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c
index 7783a874640a..4ab9cebee218 100644
--- a/fs/bcachefs/journal_io.c
+++ b/fs/bcachefs/journal_io.c
@@ -1449,7 +1449,7 @@ void bch2_journal_write(struct closure *cl)
 	if (bch2_csum_type_is_encryption(JSET_CSUM_TYPE(jset)))
 		validate_before_checksum = true;
 
-	if (le32_to_cpu(jset->version) <= bcachefs_metadata_version_inode_btree_change)
+	if (le32_to_cpu(jset->version) < bcachefs_metadata_version_current)
 		validate_before_checksum = true;
 
 	if (validate_before_checksum &&
diff --git a/fs/bcachefs/recovery.c b/fs/bcachefs/recovery.c
index 596f7c1e4245..a3a6abb88d6f 100644
--- a/fs/bcachefs/recovery.c
+++ b/fs/bcachefs/recovery.c
@@ -998,6 +998,13 @@ int bch2_fs_recovery(struct bch_fs *c)
 		goto err;
 	}
 
+	if (!(c->sb.compat & (1ULL << BCH_COMPAT_bformat_overflow_done))) {
+		bch_err(c, "filesystem may have incompatible bkey formats; run fsck from the compat branch to fix");
+		ret = -EINVAL;
+		goto err;
+
+	}
+
 	if (!(c->sb.features & (1ULL << BCH_FEATURE_alloc_v2))) {
 		bch_info(c, "alloc_v2 feature bit not set, fsck required");
 		c->opts.fsck = true;
@@ -1340,6 +1347,7 @@ int bch2_fs_initialize(struct bch_fs *c)
 			S_IFDIR|S_IRWXU|S_IRUGO|S_IXUGO, 0, NULL);
 	root_inode.bi_inum = BCACHEFS_ROOT_INO;
 	bch2_inode_pack(c, &packed_inode, &root_inode);
+	packed_inode.inode.k.p.snapshot = U32_MAX;
 
 	err = "error creating root directory";
 	ret = bch2_btree_insert(c, BTREE_ID_inodes,
diff --git a/fs/bcachefs/tests.c b/fs/bcachefs/tests.c
index 286587a118fe..3de48c593963 100644
--- a/fs/bcachefs/tests.c
+++ b/fs/bcachefs/tests.c
@@ -483,6 +483,7 @@ static int rand_insert(struct bch_fs *c, u64 nr)
 	for (i = 0; i < nr; i++) {
 		bkey_cookie_init(&k.k_i);
 		k.k.p.offset = test_rand();
+		k.k.p.snapshot = U32_MAX;
 
 		ret = __bch2_trans_do(&trans, NULL, NULL, 0,
 			__bch2_btree_insert(&trans, BTREE_ID_xattrs, &k.k_i));