Re: [PATCH] entry: check for fstat() errors after checkout

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 21, 2020, 20:00 UTC
Message-ID: <xmqq1rl48wpt.fsf@gitster.c.googlers.com>
In-Reply-To: <CAHd-oW4_A7JRmdTqCMrDU7b6-PqBSpNVD-csm3y9Bype6Vn9rA@mail.gmail.com>

Matheus Tavares Bernardino <matheus.bernardino@usp.br> writes:

Show 17 quoted lines

> I was looking further at this code and noticed that the conditions
> under which we fstat() (or lstat()) an entry are slightly different
> throughout entry.c:
>
> - In write_entry()'s footer, we call lstat() iff stat->refresh_cache.
> - In write_entry()'s `write_file_entry` label, we call fstat_output()
> when !to_tempfile.
> - In streaming_write_entry() we call fstat_output() without checking
> if !to_tempfile.
> - And, finally, in fstat_output() itself, we check
> `state->refresh_cache && !state->base_dir_len`.
>
> I understand we always check state->refresh_cache to avoid getting
> stat information we won't really need later, as we are not updating
> the index. But why do we check !to_tempfile and !state->base_dir_len?
> Doesn't writing to a tempfile or using a checkout prefix already imply
> !state->refresh_cache?

You can easily blame the code back to e4c72923 (write_entry(): use fstat() instead of lstat() when file is open, 2009-02-09). Back then, only a single place assigned 0 to state.refresh_cache and that is in "checkout-index" with either base_dir_len or to_tempfile set.

I do not remember, and I am fairly sure Stolee does not remember either. If I have to guess, this was done merely to be extra cautious, perhaps? As refresh_cache bit is checked first, check for !to_tempfile and !base_dir_len would be dead at best and redundant at worst.