bcachefs: Fix bkey format generation for 32 bit fields

Having a packed format that can represent a field larger than the
unpacked type breaks bkey_packed_successor() assertions - we need to fix this to start using the snapshot filed.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs_format.h

@@ -1374,6 +1374,7 @@ enum bch_sb_compat {
 	BCH_COMPAT_FEAT_ALLOC_INFO		= 0,
 	BCH_COMPAT_FEAT_ALLOC_METADATA		= 1,
 	BCH_COMPAT_FEAT_EXTENTS_ABOVE_BTREE_UPDATES_DONE = 2,
+	BCH_COMPAT_FEAT_BFORMAT_OVERFLOW_DONE	= 3,
 };
 
 /* options: */

fs/bcachefs/bkey.c

@@ -554,7 +554,12 @@ void bch2_bkey_format_add_pos(struct bkey_format_state *s, struct bpos p)
 static void set_format_field(struct bkey_format *f, enum bch_bkey_fields i,
 			     unsigned bits, u64 offset)
 {
-	offset = bits == 64 ? 0 : min(offset, U64_MAX - ((1ULL << bits) - 1));
+	unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
+	u64 unpacked_max = ~((~0ULL << 1) << (unpacked_bits - 1));
+
+	bits = min(bits, unpacked_bits);
+
+	offset = bits == unpacked_bits ? 0 : min(offset, unpacked_max - ((1ULL << bits) - 1));
 
 	f->bits_per_field[i]	= bits;
 	f->field_offset[i]	= cpu_to_le64(offset);

fs/bcachefs/move.c

@@ -829,13 +829,38 @@ static enum data_cmd migrate_btree_pred(struct bch_fs *c, void *arg,
 	return migrate_pred(c, arg, bkey_i_to_s_c(&b->key), io_opts, data_opts);
 }
 
+static bool bformat_needs_redo(struct bkey_format *f)
+{
+	unsigned i;
+
+	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] > unpacked_bits)
+			return true;
+
+		if ((f->bits_per_field[i] == unpacked_bits) && field_offset)
+			return true;
+
+		if (((field_offset + ((1ULL << f->bits_per_field[i]) - 1)) &
+		     unpacked_mask) <
+		    field_offset)
+			return true;
+	}
+
+	return false;
+}
+
 static enum data_cmd rewrite_old_nodes_pred(struct bch_fs *c, void *arg,
 					    struct btree *b,
 					    struct bch_io_opts *io_opts,
 					    struct data_opts *data_opts)
 {
 	if (b->version_ondisk != c->sb.version ||
-	    btree_node_need_rewrite(b)) {
+	    btree_node_need_rewrite(b) ||
+	    bformat_needs_redo(&b->format)) {
 		data_opts->target		= 0;
 		data_opts->nr_replicas		= 1;
 		data_opts->btree_insert_flags	= 0;
@@ -856,6 +881,7 @@ int bch2_scan_old_btree_nodes(struct bch_fs *c, struct bch_move_stats *stats)
 	if (!ret) {
 		mutex_lock(&c->sb_lock);
 		c->disk_sb.sb->compat[0] |= 1ULL << BCH_COMPAT_FEAT_EXTENTS_ABOVE_BTREE_UPDATES_DONE;
+		c->disk_sb.sb->compat[0] |= 1ULL << BCH_COMPAT_FEAT_BFORMAT_OVERFLOW_DONE;
 		c->disk_sb.sb->version_min = c->disk_sb.sb->version;
 		bch2_write_super(c);
 		mutex_unlock(&c->sb_lock);

fs/bcachefs/recovery.c

@@ -1201,7 +1201,8 @@ int bch2_fs_recovery(struct bch_fs *c)
 		bch_verbose(c, "quotas done");
 	}
 
-	if (!(c->sb.compat & (1ULL << BCH_COMPAT_FEAT_EXTENTS_ABOVE_BTREE_UPDATES_DONE))) {
+	if (!(c->sb.compat & (1ULL << BCH_COMPAT_FEAT_EXTENTS_ABOVE_BTREE_UPDATES_DONE)) ||
+	    !(c->sb.compat & (1ULL << BCH_COMPAT_FEAT_BFORMAT_OVERFLOW_DONE))) {
 		struct bch_move_stats stats = { 0 };
 
 		bch_verbose(c, "scanning for old btree nodes");
@@ -1287,6 +1288,7 @@ int bch2_fs_initialize(struct bch_fs *c)
 	c->disk_sb.sb->features[0] |= 1ULL << BCH_FEATURE_atomic_nlink;
 	c->disk_sb.sb->features[0] |= BCH_SB_FEATURES_ALL;
 	c->disk_sb.sb->compat[0] |= 1ULL << BCH_COMPAT_FEAT_EXTENTS_ABOVE_BTREE_UPDATES_DONE;
+	c->disk_sb.sb->compat[0] |= 1ULL << BCH_COMPAT_FEAT_BFORMAT_OVERFLOW_DONE;
 
 	bch2_write_super(c);
 	mutex_unlock(&c->sb_lock);