bcachefs: Fix a trans path overflow in bch2_btree_delete_range_trans()

bch2_btree_delete_range_trans() was using btree_trans_too_many_iters()
to avoid path overflow, but this was buggy here (and also
btree_trans_too_many_iters() is suspect in general).

btree_trans_too_many_iters() only returns true when we're close to the
maximum number of paths - within 8 - but extent insert/delete assumes
that it can use more paths than that.

Instead, we need to call bch2_trans_begin() on every loop iteration.
Since we don't want to call bch2_trans_begin() (restarting the outer
transaction) if the call was a no-op - if we had no work to do - we have
to structure things a bit oddly.

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

diff --git a/fs/bcachefs/btree_update_leaf.c b/fs/bcachefs/btree_update_leaf.c
index 31b60864b6da85a3bf8d86d29947dc6c35b080c1..98030f22ee05c9d3738b76c522e6f87bf8b69bd2 100644 (file)
--- a/fs/bcachefs/btree_update_leaf.c
+++ b/fs/bcachefs/btree_update_leaf.c
@@ -1651,15 +1651,18 @@ int bch2_btree_delete_range_trans(struct btree_trans *trans, enum btree_id id,
        int ret = 0;
 
        bch2_trans_iter_init(trans, &iter, id, start, BTREE_ITER_INTENT);
-retry:
-       while ((k = bch2_btree_iter_peek(&iter)).k &&
-              !(ret = bkey_err(k) ?:
-                btree_trans_too_many_iters(trans)) &&
-              bkey_cmp(iter.pos, end) < 0) {
+       while ((k = bch2_btree_iter_peek(&iter)).k) {
                struct disk_reservation disk_res =
                        bch2_disk_reservation_init(trans->c, 0);
                struct bkey_i delete;
 
+               ret = bkey_err(k);
+               if (ret)
+                       goto err;
+
+               if (bkey_cmp(iter.pos, end) >= 0)
+                       break;
+
                bkey_init(&delete.k);
 
                /*
@@ -1688,23 +1691,27 @@ retry:
 
                        ret = bch2_extent_trim_atomic(trans, &iter, &delete);
                        if (ret)
-                               break;
+                               goto err;
                }
 
                ret   = bch2_trans_update(trans, &iter, &delete, update_flags) ?:
                        bch2_trans_commit(trans, &disk_res, journal_seq,
                                          BTREE_INSERT_NOFAIL);
                bch2_disk_reservation_put(trans->c, &disk_res);
+err:
+               /*
+                * the bch2_trans_begin() call is in a weird place because we
+                * need to call it after every transaction commit, to avoid path
+                * overflow, but don't want to call it if the delete operation
+                * is a no-op and we have no work to do:
+                */
+               bch2_trans_begin(trans);
+
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+                       ret = 0;
                if (ret)
                        break;
        }
-
-       if (bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
-               bch2_trans_begin(trans);
-               ret = 0;
-               goto retry;
-       }
-
        bch2_trans_iter_exit(trans, &iter);
 
        if (!ret && trans_was_restarted(trans, restart_count))