bcachefs: Add BTREE_PTR_RANGE_UPDATED

This is so that when we discover btree topology issues, we can just
update the pointer to a btree node and signal btree read path that the
min/max keys in the node header should be updated from the node pointer.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs_format.h

@@ -607,13 +607,14 @@ struct bch_btree_ptr_v2 {
 	__u64			mem_ptr;
 	__le64			seq;
 	__le16			sectors_written;
-	/* In case we ever decide to do variable size btree nodes: */
-	__le16			sectors;
+	__le16			flags;
 	struct bpos		min_key;
 	__u64			_data[0];
 	struct bch_extent_ptr	start[];
 } __attribute__((packed, aligned(8)));
 
+LE16_BITMASK(BTREE_PTR_RANGE_UPDATED,	struct bch_btree_ptr_v2, flags, 0, 1);
+
 struct bch_extent {
 	struct bch_val		v;
 

fs/bcachefs/btree_io.c

@@ -753,6 +753,11 @@ static int validate_bset(struct bch_fs *c, struct btree *b,
 			struct bch_btree_ptr_v2 *bp =
 				&bkey_i_to_btree_ptr_v2(&b->key)->v;
 
+			if (BTREE_PTR_RANGE_UPDATED(bp)) {
+				b->data->min_key = bp->min_key;
+				b->data->max_key = b->key.k.p;
+			}
+
 			btree_err_on(bkey_cmp(b->data->min_key, bp->min_key),
 				     BTREE_ERR_MUST_RETRY, c, b, NULL,
 				     "incorrect min_key: got %llu:%llu should be %llu:%llu",

fs/bcachefs/btree_update_interior.c

@@ -297,7 +297,6 @@ static struct btree *bch2_btree_node_alloc(struct btree_update *as, unsigned lev
 		bp->v.mem_ptr		= 0;
 		bp->v.seq		= b->data->keys.seq;
 		bp->v.sectors_written	= 0;
-		bp->v.sectors		= cpu_to_le16(c->opts.btree_node_size);
 	}
 
 	if (c->sb.features & (1ULL << BCH_FEATURE_new_extent_overwrite))

fs/bcachefs/extents.c

@@ -214,9 +214,8 @@ void bch2_btree_ptr_v2_to_text(struct printbuf *out, struct bch_fs *c,
 {
 	struct bkey_s_c_btree_ptr_v2 bp = bkey_s_c_to_btree_ptr_v2(k);
 
-	pr_buf(out, "seq %llx sectors %u written %u min_key ",
+	pr_buf(out, "seq %llx written %u min_key ",
 	       le64_to_cpu(bp.v->seq),
-	       le16_to_cpu(bp.v->sectors),
 	       le16_to_cpu(bp.v->sectors_written));
 
 	bch2_bpos_to_text(out, bp.v->min_key);
@@ -1081,10 +1080,9 @@ const char *bch2_bkey_ptrs_invalid(const struct bch_fs *c, struct bkey_s_c k)
 	unsigned nonce = UINT_MAX;
 	unsigned i;
 
-	if (k.k->type == KEY_TYPE_btree_ptr)
+	if (k.k->type == KEY_TYPE_btree_ptr ||
+	    k.k->type == KEY_TYPE_btree_ptr_v2)
 		size_ondisk = c->opts.btree_node_size;
-	if (k.k->type == KEY_TYPE_btree_ptr_v2)
-		size_ondisk = le16_to_cpu(bkey_s_c_to_btree_ptr_v2(k).v->sectors);
 
 	bkey_extent_entry_for_each(ptrs, entry) {
 		if (__extent_entry_type(entry) >= BCH_EXTENT_ENTRY_MAX)