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Date: Mon, 17 Feb 2020 20:19:40 +0300
From: Konstantin Osipov <kostja.osipov@gmail.com>
Message-ID: <20200217171940.GD11553@atlas>
References: <20200217155953.25803-1-gorcunov@gmail.com>
<20200217155953.25803-5-gorcunov@gmail.com>
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Subject: Re: [Tarantool-patches] [PATCH 4/4] box/txn: fix nil dereference in
txn_rollback
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To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: tml <tarantool-patches@dev.tarantool.org>
* Cyrill Gorcunov <gorcunov@gmail.com> [20/02/17 20:08]:
> In case if we get failed in allocation of new
> journal entry the txn_rollback will try to
> derefernce nil pointer
This is lgtm (apart from typos in the comment), however,
I think this patch is incomplete, since wal_write() still calls
rollback on failure to queue the task to cbus.
Could you please remove txn_rollback() from wal_write in scope of
this series?
I mean this part:
fail:
entry->res = -1;
journal_entry_complete(entry);
return -1;
}
(remove jounral_entry_complete() from here).
I think once you remove journal_entry_complete (which basically
calls rollback), you will be able to remove this ugly
"cleanr-then-restore" of txn as well:
> + /*
> + * Queue the entry for processing in journal
> + * engine. The semantics of complete_cb implies
> + * that fiber's txn (kept in storage) is nil
> + * becase WAL is a separet thread, for this
> + * sake we zap it here.
> + *
> + * Still this is messy since the caller runs
> + * txn_rollback if something bad happened. Thus
> + * restore the former txn on error path.
> + */
> + fiber_set_txn(fiber(), NULL);
> if (journal_write(req) < 0) {
> + fiber_set_txn(fiber(), txn);
> diag_set(ClientError, ER_WAL_IO);
> diag_log();
> return -1;
--
Konstantin Osipov, Moscow, Russia
https://scylladb.com