bcachefs: Split extents if necessary in bch2_trans_update()

Currently, we handle multiple overlapping extents in the same
transaction commit by doing fixups in bch2_trans_update() - this patch
extents that to split updates when necessary. The next patch that
changes the reflink code to not fragment extents when making them
indirect will require this.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_update_leaf.c

@@ -1099,9 +1099,30 @@ int bch2_trans_update(struct btree_trans *trans, struct btree_iter *iter,
 		if (i < trans->updates + trans->nr_updates &&
 		    i->btree_id == n.btree_id &&
 		    bkey_cmp(n.k->k.p, bkey_start_pos(&i->k->k)) > 0) {
-			/* We don't handle splitting extents here: */
-			BUG_ON(bkey_cmp(bkey_start_pos(&n.k->k),
-					bkey_start_pos(&i->k->k)) > 0);
+			if (bkey_cmp(bkey_start_pos(&n.k->k),
+				     bkey_start_pos(&i->k->k)) > 0) {
+				struct btree_insert_entry split = *i;
+				int ret;
+
+				BUG_ON(trans->nr_updates + 1 >= BTREE_ITER_MAX);
+
+				split.k = bch2_trans_kmalloc(trans, bkey_bytes(&i->k->k));
+				ret = PTR_ERR_OR_ZERO(split.k);
+				if (ret)
+					return ret;
+
+				bkey_copy(split.k, i->k);
+				bch2_cut_back(bkey_start_pos(&n.k->k), split.k);
+
+				split.iter = bch2_trans_get_iter(trans, split.btree_id,
+								 bkey_start_pos(&split.k->k),
+								 BTREE_ITER_INTENT);
+				split.iter->flags |= BTREE_ITER_KEEP_UNTIL_COMMIT;
+				bch2_trans_iter_put(trans, split.iter);
+				array_insert_item(trans->updates, trans->nr_updates,
+						  i - trans->updates, split);
+				i++;
+			}
 
 			/*
 			 * When we have an extent that overwrites the start of another

fs/bcachefs/io.c

@@ -342,9 +342,8 @@ int bch2_extent_update(struct btree_trans *trans,
 		bch2_trans_iter_put(trans, inode_iter);
 	}
 
-	bch2_trans_update(trans, iter, k, 0);
-
-	ret = bch2_trans_commit(trans, disk_res, journal_seq,
+	ret =   bch2_trans_update(trans, iter, k, 0) ?:
+		bch2_trans_commit(trans, disk_res, journal_seq,
 				BTREE_INSERT_NOCHECK_RW|
 				BTREE_INSERT_NOFAIL);
 	if (ret)

fs/bcachefs/reflink.c

@@ -155,7 +155,9 @@ static int bch2_make_extent_indirect(struct btree_trans *trans,
 	*refcount	= 0;
 	memcpy(refcount + 1, &orig->v, bkey_val_bytes(&orig->k));
 
-	bch2_trans_update(trans, reflink_iter, r_v, 0);
+	ret = bch2_trans_update(trans, reflink_iter, r_v, 0);
+	if (ret)
+		goto err;
 
 	r_p = bch2_trans_kmalloc(trans, sizeof(*r_p));
 	if (IS_ERR(r_p)) {
@@ -168,7 +170,7 @@ static int bch2_make_extent_indirect(struct btree_trans *trans,
 	set_bkey_val_bytes(&r_p->k, sizeof(r_p->v));
 	r_p->v.idx = cpu_to_le64(bkey_start_offset(&r_v->k));
 
-	bch2_trans_update(trans, extent_iter, &r_p->k_i, 0);
+	ret = bch2_trans_update(trans, extent_iter, &r_p->k_i, 0);
 err:
 	if (!IS_ERR(reflink_iter))
 		c->reflink_hint = reflink_iter->pos.offset;