bcachefs: Don't allocate stripes at POS_MIN

In the future, stripe index 0 will be a sentinal value. This patch
doesn't disallow stripes at POS_MIN yet, leaving that for when we do the
on disk format changes.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey.h

@@ -178,6 +178,11 @@ static inline struct bpos bpos_min(struct bpos l, struct bpos r)
 	return bkey_cmp(l, r) < 0 ? l : r;
 }
 
+static inline struct bpos bpos_max(struct bpos l, struct bpos r)
+{
+	return bkey_cmp(l, r) > 0 ? l : r;
+}
+
 void bch2_bpos_swab(struct bpos *);
 void bch2_bkey_swab_key(const struct bkey_format *, struct bkey_packed *);
 

fs/bcachefs/ec.c

@@ -690,7 +690,8 @@ static int ec_stripe_bkey_insert(struct bch_fs *c,
 	struct btree_trans trans;
 	struct btree_iter *iter;
 	struct bkey_s_c k;
-	struct bpos start_pos = POS(0, c->ec_stripe_hint);
+	struct bpos min_pos = POS(0, 1);
+	struct bpos start_pos = bpos_max(min_pos, POS(0, c->ec_stripe_hint));
 	int ret;
 
 	bch2_trans_init(&trans, c, 0, 0);
@@ -701,7 +702,7 @@ static int ec_stripe_bkey_insert(struct bch_fs *c,
 			   BTREE_ITER_SLOTS|BTREE_ITER_INTENT, k, ret) {
 		if (bkey_cmp(k.k->p, POS(0, U32_MAX)) > 0) {
 			if (start_pos.offset) {
-				start_pos = POS_MIN;
+				start_pos = min_pos;
 				bch2_btree_iter_set_pos(iter, start_pos);
 				continue;
 			}